realistic rations · v introduction section 1 understanding the dairy cow and her feed 1.1 aims of...

D A I R Y L I N K — R E A L I S T I C R A T I O N S

Realistic Rations

Diane Ryan, NSW Agriculture, Camden

Scott Barnett, ProDairy, Scone

Vicki MacDonald, Elanco Animal Health, South Australia


Acknowledgments

Edited, designed and desktop published by Ann Munroe, Sydney, andMatthew Stevens, ScienceScape Editing, Sydney

Alex Ashwood, Program Leader (Dairy Nutrition and Management),Wollongbar

Stuart Court, Ridley’s Animal Products, Tamworth

Roy Kellaway, University of Sydney

Ian Lean, Consultant, Bovine Australasia, NSW

J. Gooden, University of Sydney (ACF Nutrition School Notes)

Department of Primary Industry, South Australia

Agriculture Victoria

Hoard’s Dairyman

Agdex 411/60

ISBN 0 7310 9816 1 (Dairylink monographic series)ISBN 0 7310 9810 X (Realistic Rations)

© NSW Agriculture 1997

This publication is copyright. Except as permitted under the CopyrightAct 1968 (Cth), no part of this publication may be produced by anyprocess, electronic or otherwise, without the specific written permission ofthe copyright owner. Neither may information be stored electronically inany form whatever without such permission.

NSW Agriculture does not accept any form of liability, be it contractual,tortious or otherwise, for the contents of this publication or for anyconsequences arising from its use or any reliance placed upon it. Theinformation, opinions and advice contained in this publication are of ageneral nature only and may not relate or be relevant to your particularcircumstances.

Pesticides Act 1978

Under the Pesticides Act you must use only a registered chemical. It mustnot be used for any purpose or in any way contrary to the directions onthe label unless a permit has been obtained under the Act.


iii

Foreword

Dairying is one of the most progressive rural industries in NSW.This is evidenced by substantial changes in herd sizes andincreases in production by cows and from farms.

An outcome of these increases is that management hasbecome more complex, requiring greater knowledge andtechnical skills.

As farmers become more competitive through increases inboth production and productivity, they will require even bettertechnical information and management skills. Most important,they will need to know how to use the information in improvingwhole-farm performance and profits. This statement is supportedby results of various Dairy Research and DevelopmentCorporation workshops and NSW Dairy Farmers’ Associationsurveys, which have clearly indicated that farmers requiretechnical packages that are current and relevant.

DairyLink is a series of integrated information packages thatlook at aspects of pasture, herd and feed management, andsuggest practical ways of getting the best from your cows andpastures. The DairyLink series is a result of collaborationbetween NSW Agriculture officers, agribusiness and farmers.

The packages will be the basis of workshops and meetings forNSW dairy farmers.

DairyLink has much to offer the NSW dairy industry inhelping improve farm productivity and profitability. Weencourage farmers to attend and participate in the DairyLinkworkshops and meetings.

Reg Smith, President,NSW Dairy Farmers’Association

Kevin Sheridan,Director-General,NSW Agriculture

John Craven, ProgramManager, FarmProduction, DRDC


iv

Preface

DairyLink is an innovative concept that introduces you to someimportant technical areas to help improve farm productivity andprofits.

The modules in the series are of value to farmers, students,consultants and extension service providers.

DairyLink consists of the following information packages:

Establishing PasturesManaging PasturesGrowing HeifersRealistic RationsConserving Feed

The modules have been developed as technical manuals andfarmer-friendly booklets, and are linked to the Tocal Dairy HomeStudy course.

I would like to take this opportunity to acknowledge andthank the various technical teams for doing an excellent job. Ialso appreciate the funding and support provided by DRDC.

Alex AshwoodDairyLink Series Coordinator


Contents

v

Introduction

Section 1Understanding the dairy cow and her feed 1.1Aims of this section 1.1How do cows use feed? 1.1How do we measure feed value? 1.5How much feed can a cow eat? 1.11What nutrients does the cow need? 1.15What feeds supply these nutrients? 1.25Getting value from feed analysis 1.32

Section 2

Costing pasture & supplements 2.1Aims of this section 2.2Why not feed pasture alone? 2.2How much does pasture cost? 2.4Why use supplements? 2.5How do I use supplements sensibly? 2.7How do I choose a cost-effective supplement? 2.9

Section 3Working out a ration 3.1Aims of this section 3.1Guidelines for feeding dairy cattle at different stages of lactation 3.1What else do I need to know before I can balance a cow’s diet? 3.1Working out whether a ration is adequate 3.5Can I use a computer for ration balancing? 3.12

Section 4Fine-tuning your feeding 4.1Aims of this section 4.1Body condition scoring 4.1Understanding the metabolic and nutritional diseases of dairy cows 4.3Changing milk composition by changing the ration 4.7Transition feeding 4.10

AppendixesAppendix 1: Measuring dry matter A.1Appendix 2: Minerals and vitamins for the lactating cow A.2

Further information


vi


Introduction 1

Introduction

When we are feeding a dairy cow, we are trying to achieve anaim. We want the cow to produce a certain amount of milk, to getpregnant and keep healthy. If the cow is a heifer, we want her togrow and be a productive cow in her maturity.

The feeding system we use to achieve our aims should bebased on both scientific and practical knowledge. We should havea good understanding of the relationship between the cow and herfeed. We should understand what makes up a cow’s diet and howit can be manipulated.

Realistic Rations is one of a series of DairyLink publicationssponsored by the Dairy Research and Development Corporation.It is a practical step-by-step guide that will take the mystery outof ration formulation. It assumes that you have a goodbackground in pasture establishment and management, grazingmanagement and the conservation of forages; these subjects arecovered by the companion volumes of DairyLink.

NSW Agriculture has worked closely with agribusiness,farmers and research officers to produce this publication.

Diane RyanNSW AgricultureElizabeth Macarthur Agricultural InstituteCamdenPhone (046) 29 3333

Fax (046) 29 3300


Introduction 2


1.1

Understanding the dairy cow & her feed

Figure 1.1: The cow’s digestive system

Aims of this section

Feeding a dairy cow means more thanpresenting adequate food. The dairy cowhas special requirements which her diethas to provide. Today’s dairy farmers needto be aware of these requirements; whenyou are determining how your cows willbe fed you should know what feeds arethe best to use.

Completing this section will give you agreater knowledge of:

• how a cow breaks down feed for herbody to use

• the importance of the rumen and itsbacteria

• how to determine the value of a feed

• the different components measured infeed and what they mean

• how much a cow can eat

• what nutrients are needed by the cow

• how much of these nutrients is requiredby the cow for health, growth,pregnancy and milk production

• what feeds supply different nutrients

• practical tips for getting good results

affect ration formulation.

How do cows use feed?

What is the cow’s digestive system andhow does it work?

Anatomy of the digestivesystem

The digestive system of ruminants (forexample, cows, sheep and deer) differsfrom that of other animals because it has a

when feeds are sent away to beanalysed.

Knowledge level required

To understand this section you need apractical knowledge of dairy cows anddairy farming. Reading the DairyLinkmanual Conserving Feed will give yousome valuable background on the typesand values of different silages and hays.

Information in the DairyLink manualsEstablishing Pastures and ManagingPastures provides details of pasture costsand grazing management, both of which


1.2

four chambered stomach, not a singlestomach. Figure 1.1 shows the cow’sdigestive system.

The digestive system starts at the mouthand ends at the anus. It is a continuous tubethat has special functions along its length,and has a number of accessories, calledglands, which help it work.

The digestive system’s main functionsare intake of food, breakdown of food intocompounds which can be used by thebody (digestion), transport of thecompounds into the body (absorption) andelimination of waste.

The mouth of the cow is well designedfor ripping pasture and grinding feed.

The tongue is extremely movable andhas a covering of sharp, backward-pointing projections that help direct foodtowards the throat.

The teeth are designed for grindingand chopping. There are no upper frontteeth (incisors)—instead, there is a dentalplate which the lower incisors come intocontact with.

The dental pattern for an adult cow is:Upper Jaw Lower Jaw

Left Right Left RightIncisors 0 0 4 4Canine 0 0 0 0Premolars 3 3 3 3

Molars 3 3 3 3

There are six glands which producesaliva to aid the initial digestion of food(salivary glands). Two glands are situatedbelow the ear (parotid), two near the backof the throat (mandibular) and two underthe tongue (sublingual). These glandsproduce 70–180 litres of alkaline (pH 7.7–8.7) saliva each day. The volume of salivaproduced depends on the diet.

The pharynx is the cavity between themouth and the opening of theoesophagus. The oesophagus is themuscular tube from the pharynx to thestomach. Food can be moved either up ordown the oesophagus by muscular

Food consists of chemical compounds(such as proteins, starch and fibre) whichcannot be used by the animal unless theyare broken down into smaller components.

contractions.The stomach has four chambers. It

fills the left-hand side of the abdomen,pushing the rest of the digestive tract tothe right-hand side.

The four parts of the stomach are therumen (‘paunch’), reticulum(‘honeycomb’), omasum (‘bible’) andabomasum (which is similar to the singlestomach of non-ruminants). The rumencontains microbes which aid digestion offood.

In the young ruminant, a grooveformed by two muscular folds runs alongthe top wall of the rumen area, connectingthe oesophagus with the abomasum. Thisreticular or oesophageal groove isstimulated by the action of suckling andallows colostrum and milk to bypass theimmature rumen. If the calf has access tohay and grain from the first week of life,the rumen-reticulum begins to functionand should be fully functional and able todigest forages by the third or fourth weekof life.

The small intestine leaves theabomasum and sits in the right-hand sideof the abdomen. It is about 40 metres longand has three parts, the duodenum,jejunum and ileum. The gall bladderand pancreas are two glands along thispart of the digestive tract; they providesecretions that help digestion in thissection of the gut.

The large intestine sits in the upperright part of the abdomen. It consist of thecaecum (similar to our appendix), colonand rectum. The caecum and colon,similar to the rumen, contain microbesthat aid digestion.

How digestion works


1.3

Figure 1.2: How the cow digests food

These components are transported into theblood system and circulated throughoutthe body to be used by the differentorgans. In the organs, the components canbe rebuilt into other compounds which thebody can use. For example, compoundsreaching the udder by the blood can bemade into milk fat and milk protein.Figure 1.2 shows how the cow digestsfood.

This process of breaking down andrebuilding components is known asmetabolism.

Enzymes are special proteins whichhelp drive the chemical reactions involvedin breaking down or rebuildingcompounds. In single-stomach animals,such as dogs and cats, glands associatedwith the digestive system are the mainsource of the enzymes needed fordigestion. In ruminants, enzymes releasedby microbes in the rumen digest about65% of food.

How the cow’s stomach digests food

Ruminants digest feeds primarily byfermentation by microbes in the rumen.

These microbes have specific functions.One group (anaerobic bacteria, protozoaand fungi) break down carbohydrates inthe diet. Another group (anaerobicbacteria and some fungi) break down thestructural fibre of plants. There is aworking relationship between themicrobes: the fungi might start thefermentation process by attacking theplant cell walls, then other microbes breakdown the products released into smallercompounds which are absorbed by thecow or else are used by the microbes fortheir own growth.

The rumen-reticulum first receivesthe food entering the stomach complex. Itis similar to a large fermentation vessel.The feedstuffs and the rumen microbesare continually mixed by muscularcontractions of the wall of the rumen. Thefeed may be digested by enzymesproduced by microbes or present in thesaliva. Because many compoundsproduced during digestion are acid, thesaliva helps buffer the rumen, maintainingthe ‘neutral’ (pH 5.8–6.8) environmentneeded by the microbes. Some of the


1.4

digested product (ammonia and volatilefatty acids) may be absorbed through therumen wall into the blood. Gas (methaneand carbon dioxide) may be producedduring the digestion process and isbelched out of the rumen.Energy, in theform of the molecule AdenosineTriphosphate (ATP), is taken up by themicrobes for their growth.

Fibrous feed is regurgitated up theoesophagus to the mouth to be morethoroughly chewed and reduced in sizebefore it is reswallowed; this is known asrumination or ‘chewing the cud’. On agrass-based diet, twice the amount of dryfeed material as was originally eatenpasses through the cycle of rumination.The small particles of food then pass on tothe reticulum and omasum. The valvebetween the reticulum and omasum keepsfeed particles in the rumen until they areless than 1–2 mm in size.

The omasum absorbs 30–60% ofwater leaving the rumen-reticulum. Thewater contains products of digestion suchas volatile fatty acids and minerals.

The abomasum is the equivalent of anon-ruminant’s stomach. It has acidsecretions that break down escaped rumenmicrobes and other compounds so thatthey are ready for digestion by the smallintestine.

The small intestine digests andabsorbs any fat or protein not digested bythe rumen, as well as some of the solublecarbohydrate. Escaped rumen microbesare digested and their protein absorbed.

The indigestible products pass into thelarge intestine, where they undergo asecond fermentation. Only 5–10% of thetotal digestion of feed occurs in the largeintestine. It contains microbes that attackthe insoluble carbohydrates and starch.Any volatile fatty acids produced(together with minerals and water) areabsorbed. The microbes from the largeintestine pass out with the undigested

material in the faeces.

Feeding the rumen

The fibrous pasture and forages in a cow’sdiet must be digested through the activityof microbes. Without these microbes, thecow will die. Feeding too much grain cancause certain microbes to break down thecarbohydrates in the grain, in preference tomicrobes which break down fibre. If theexcessive amounts of acid produced fromthe breakdown of the grain cannot beneutralised by the cow’s high pH saliva,the pH of the rumen decreases (becomesacidic). Certain microbes that are not suitedto the acidic conditions may be killed.Damage can occur to parts of the rumenwall—especially the folds, which areimportant for absorbing compounds intothe blood. Carbon dioxide gas can build upin the top of the rumen and can ‘bloat’ therumen unless it is able to be ‘burped’. Atone extreme the end result is poor digestionof fibre-based feeds; at the other extremethe cow becomes sick and dies.

It is important to make sure the rumen isfunctioning properly when you startfeeding a cow. To do this, you mustunderstand how to get a proper balance offeed types in the ration.

The value of a feed and its usefulness to ananimal are determined by what it containsand how much of it is eaten. The nutritivevalue of a feed is determined by thefollowing:

• what is in the feed

• how it is digested by the rumenmicrobes and by the cow

• the physiological state of the cow.

How do we measure feedvalue?

Feed analysis

Feed analysis determines what is present


1.5

Table 1.1: Brewers’ grain—proximate analysis

in a feed—it measures only one part of afeed’s nutritive value. Feed analysis is donewith special equipment in a laboratory,although in the future it will be possible todo analyses on-farm.

Proximate analysis is the chemicalanalysis of feed to assess its nutrientcontent. Table 1.1 shows the results of aproximate analysis of a feed.

Dry matter, metabolisable energy,crude protein and digestibility are someof the components determined. What dothese components mean? In this section,the following components which make upthe proximate analysis of feed will beexplained.

Dry Matter (DM)

• Dry matter intake (DMI)

Energy

• Gross Energy (GE)

• Digestible Energy (DE)

• Metabolisable Energy (ME)

• Net Energy System (NEl, NEm,NEp)

• Total Digestible Nutrients (TDN)

Protein

• Non protein nitrogen (NPN)

• Rumen Degradable Protein (RDP)

• Undegraded Dietary Protein (UDP)

• Bypass Protein

• Protein degradability (Pdg%)

Carbohydrates

• Fibre —Neutral Detergent Fibre (NDF) —Acid Detergent Fibre (ADF) —Lignin

—Crude Fibre (CF)

• Non-structural carbohydrates (NSC)

• Non-fibre carbohydrates (NFC)

Fats and oils

• Crude fat

Digestibility

• DMD

Dry matter

Dry matter (DM) is the feed materialremaining after a feed sample is dried sothat all moisture is removed. Water, whichis present in all feeds, does not provideany nutrients or energy needed by the cow.Dry matter is used as a measure of thequantity of feed that is fed to a cow.

Dry matter intake is the quantity ofmoisture-free feed consumed by a cow in a24-hour period.

Some nutrients in a feed (such as crudeprotein, neutral detergent fibre, aciddetergent fibre and minerals) are calculatedas a percentage of the ration’s dry matter;others (such as energy) are calculated as avalue per kilogram of dry matter.

The values of different feeds can be

Component Value

Dry matter (DM) 26.0%

Nitrogen 3.2%

Crude protein 19.8%

Acid detergent fibre 30.1%

Digestible dry matter 67.1%

Metabolisable energy 10.1 MJ/kg DM


1.6

compared by relating them to their drymatter content. It is important to knowthe dry matter content of feeds whenyou are changing from one feed toanother in a ration.

There are a number of laboratorymethods for measuring dry matter infeeds. A practical way of using amicrowave oven to determine dry matterpercentage is described in Appendix 1 atthe end of this manual.

Units of measurement

The dry matter percentage is the drymatter content of a sample of feed,expressed as a percentage of the wetsample. It is based on the difference inweight after the sample is dried. Appendix1 explains how to calculate dry matter

ration for a herd it is important to knowthe as fed weight, as this is important forweighing feed before mixing. To convertfrom a dry matter percentage to an as fedvalue, multiply the amount of feed on adry matter basis by the inverse of the drymatter percentage.

For example, if 100 kg DM of a feed isto be added to a ration mix, and the feedhas a dry matter percentage of 50%,then the total weight of the feed to beadded is 100 kg × 100/50 or 200 kg on anas fed basis.

Energy

Energy is needed for the normal bodyfunctions of the cow. It is the mostimportant nutrient for driving milkproduction. Energy is also needed forwalking, putting on body condition andnourishing the developing foetus if the cowis pregnant. Cows get their energy from the

Figure 1.3: Metabolisable energy is the energy available for use by the cow (adaptedfrom Agriculture Victoria, 1994)

percentage.

The amount of water present in a feed isthe inverse of the dry matter percentage. Soif a feed has a dry matter percentage of20%, then 80% of the feed is water (100 -20%).

Feeds may be described on a fresh, wetweight (‘as fed’) basis rather than a drymatter basis.When you are determining a

digestion of feed.The total energy in a feed is called its

gross energy. Not all of this energy isavailable to the cow—some of it will belost in the faeces. The remaining energy iscalled digestible energy—the portion of

ENERGY INTAKE

GROSS ENERGY

METABOLISABLE ENERGY

Faecal energy

Gas, heat & urine energy

DIGESTIBLE ENERGY

Maintenance Milk production Pregnancy Body condition


1.7

energy from the feed which is availablefor digestion.

During the process of digestion, energyis lost in the manufacture of wasteproducts which leave the body in the urineor as gas belched from the rumen(methane), and through excess heatproduction by the cow. The remainingenergy is now available to the cow forbody maintenance, milk production,pregnancy and body conditioning. Thisenergy is called metabolisable energy(see Figure 1.3).

Feeds may have similar gross energycontents but may vary in the total energyavailable for milk production and bodymaintenance. Only the energy availablefor use by the cow (metabolisable energy)is determined for different feeds. Thisenergy is expressed as megajoules ofmetabolisable energy per kilogram ofdry matter or MJME/kg DM.

The higher the MJME in a feed, thegreater the energy the feed provides to theanimal.


The basic unit of energy is a joule, whichequals 0.239 calories. One megajoule isone million joules.

The metabolisable energy system formeasuring a cow’s energy needs is used inAustralia. The results from any AustralianFeed Analysis laboratory express themetabolisable energy of the feed asMJME/kg DM.

In the USA, the net energy system isused. In the net energy system, there arethree components: net energy formaintenance (NEm), net energy forlactation (NEl) and net energy for growthand weight gain (NEg). Net energy isequivalent to metabolisable energy minusthe energy used in the process of digestionand metabolism but includes the energy inthe feed used for maintenance andproduction.

If you are reading an Americanpublication, the NEl value can beconverted to a metabolisable energy valueby dividing it by 0.62. If a total NE valueis given in megacalories, then this figurecan be converted to metabolisable energyin MJME by multiplying the value by 6.8.

If the publication expresses the resultsin megacalories instead of megajoules,convert the result to megajoules bydividing by 4.184.

Another term used in Americanpublications is total digestible nutrientsor TDN. TDN is a feed value calculatedfrom the total analysis of a feed. It iscommonly used to represent the digestibleenergy in a diet and is expressed as apercentage of gross energy. TDN can beconverted to a metabolisable energy valueby multiplying the value by 0.1476.

Protein

Feed contains the element nitrogen,which is normally found in the proteinpart of the feed. Protein is usually 16%nitrogen. Feed can also contain nitrogensfrom other sources; these are non-proteinnitrogens (NPNs), such as urea.

The percentage of crude protein in afeed is calculated by multiplying thenitrogen content by 6.25 (because proteincontains 16% or 16 in 100 parts nitrogen).This value contains both true protein andnon-protein nitrogen sources.

The nature of a protein and its passagethrough the rumen (see Figure 1.4) canaffect the following:

• the amount of protein digested andabsorbed in the rumen

• the amount of protein that passesthrough the rumen for digestion andabsorption in the small intestine.

Most protein entering the rumen can bebroken down by microbes if it is in therumen for long enough. A small amount ofprotein is indigestible by both microbial


1.8

(UDP), is not modified from its originalstate in the feedstuff. The amino acids itcontains are released to the cow when theprotein is digested in the small intestine.

In any feed, the protein will be acombination of RDP and UDP. Feeds witha high percentage of their protein as UDPare called bypass proteins. Slowing thepassage of a feed through a rumen canaffect its UDP percentage. The longertime a feed is in the rumen, the greater thechance of microbial attack and digestion.


The feed test will normally show theprotein content in the feed as crudeprotein. Crude protein is normallyexpressed as a percentage of a kilogram ofdry matter content (CP%).

To calculate the total amount of crudeprotein as grams per kilogram of drymatter in the feed, simply multiply thepercentage figure by 10.

For example, a feed can have 12%crude protein or 120 g/kg DM.

Sometimes the nitrogen value of a feedis given instead of a crude proteinpercentage. To convert the nitrogen valueto a crude protein percentage, multiply thenitrogen value by 6.25. Remember thatnot all nitrogen will be part of protein;some of the nitrogen might be non-proteinnitrogen such as urea. The nitrogen fromprotein and that from urea are notmeasured separately when a feed sampleis analysed.

The protein degradability (Pdg%) is notgiven on a feed test result. The test used todetermine this value is very expensive(about $1000) and is usually requested byfeed companies when evaluating one oftheir products. However, you can findprotein degradability percentages for anumber of feeds in the literature (NRC,1989).

The RDP value is often given as apercentage of the total crude protein. For

Figure 1.4: The components of crudeprotein (adapted from AgricultureVictoria, 1994)

and animal enzymes and will pass intactfrom the animal. No part of this protein willbe absorbed or used in metabolism.

Protein entering the rumen is brokendown by the microbes into amino acids.Most amino acids are further broken downto form ammonia, which is used by themicrobes to produce their own protein fortheir reproduction and growth. Proteinwhich is broken down in the rumen isRumen Degradable Protein (RDP).

Non-protein nitrogen is 100%degradable in the rumen. The excessammonia from NPN and proteinbreakdown is absorbed through the rumenwall into the blood and travels to the liverto be detoxified by the formation of urea.Urea is excreted from the body in theurine.

Some microbes will pass out of therumen into the abomasum. The proteinsthey contain are digested and absorbed bythe cow in the small intestine. Microbialprotein is the major source of protein forthe cow.

Protein which passes through therumen without being attacked by themicrobes will pass into the small intestineto be digested and absorbed. This protein,called Undegraded Dietary Protein

CRUDE PROTEIN

DIETARYPROTEIN

NON-PROTEINNITROGEN(NPN)

Rumendegradableprotein (RDP)

Rumenundegradableprotein (UDP)


1.9

example, the protein in a cereal grain maybe 90% degraded in the rumen.

The feed requirements for RDP andUDP are often expressed as grams per kgDM. If a feed has a CP of 12% or 120 g/kg DM and an RDP of 90%, everykilogram of feed dry matter will contain120 × 90/100g or 108 g of RDP.

be expressed as ADF, because this value isused by the laboratory in the calculationof energy. Some laboratories will providethe NDF value of the feed. Lignin can bemeasured in the feed, but it is not asuseful for balancing rations as ADF andNDF.

Some publications use the term crudefibre (CF). Crude fibre includes the ligninand most of the cellulose in the feed. Toget an approximation of CF, divide theADF value by 1.15.

Soluble carbohydrates

Non-structural carbohydrates (NSC)are the carbohydrates that are not part ofthe plant cell wall (NDF). They arepresent in the cell contents. NSC are alsocalled non-fibre carbohydrates or NFC.

NSC include soluble sugars, starchesand pectins. Sugars are an instant energysource for the rumen microbes. Starchesand pectins are storage carbohydrates thatare fermented more slowly than sugars.NSC are more completely and rapidlydigested in the rumen than the NDFcarbohydrates. They can also be digestedin the cow’s intestine. The ration shouldcontain 30–40% NSC in its total drymatter content.


Direct measures of non-structuralcarbohydrates are not carried out innormal feed analysis. NSC is usuallycalculated by subtracting all the othercomponents in the feed from 100. Thesecomponents are fibre (NDF or CF), crudeprotein (CP), fat and oil (ether extract orEE), water content (100 - DM%) andmineral content (ash). Ash is the portion offeed remaining after it has been combusted

Carbohydrates

The components of the feed that do notcontain nitrogen (and so are not included inthe crude protein determination), and all fibrecomponents, are the carbohydrates.Carbohydrates make up about 75% of aplant’s dry matter.

Fibre

Fibre provides the structural support forplants and cell walls. Feeds high in fibre arecalled roughages or forages. There are anumber of measures of a feed’s fibre content.

Neutral detergent fibre (NDF) is ameasurement of the amount of plant cell wallor ‘fibre’ in forages. When a forage is boiledin a detergent with neutral (pH 7) detergent,

all the contents of the cell dissolves exceptfor the cell wall or NDF.

NDF contains carbohydrates (celluloseand hemicellulose) that are partly digestedby the rumen bacteria but are not digestedby the cow’s intestines.

Acid detergent fibre (ADF) is theresidue of lignin and cellulose remainingwhen the plant cell wall is treated with anacidic detergent solution. ADF is a usefulmeasurement of the minimum fibre levelin a ration, and is used to help calculatethe energy value of a forage.

Lignin is the least digestible portion ofthe plant. It binds together the othercarbohydrates in the plant and gives theplant rigidity.


The fibre content in a feed will commonly

at 650°C; it is the inorganic or mineralpart of the feed.

In other words, the percentage of NSCin a feed can be calculated by the followingequation:


1.10

NSC = 100 – (CP + CF + ether extract + ash +

water content)

where all components are expressed ingrams.

Fats and oils

Fats and oils are sources of energy. Theyhave a similar structure to carbohydrates,except that they contain three fatty acidchains. For this reason they are calledtriglycerides. During breakdown(oxidation), they liberate 2.5 times moreenergy than carbohydrates of the sameweight.

if the feed contains fats or oils (forexample, oilseed meal).

Digestibility

The organic part of the feed consists ofeverything except the mineral component(ash). The organic matter contains theenergy of the feed, and there is a directrelationship between feed organic matterand gross energy. A proportion of theorganic matter of the feed isindigestible—it contains lignin and somecellulose.

The digestibility of a feed is theproportion that can be digested by ananimal. Digestibility is a guide to theenergy value of a feed. It is commonlymeasured as a percentage (%).Dry matter digestibility (DMD) = feed DM – faeces DM × 100%

feed DM

As grasses mature, the organic mattercontent becomes more indigestiblebecause the lignin content increases. Forthis reason, cows obtain greater energyfrom younger grasses; there is more feed

Figure 1.5: The relationship between digestibility and metabolisable energy (afterMAFF, 1984)


The crude fat of a feed is estimated by theether extract method. This methoddetermines all the components in the feedthat are soluble in ether—all the fats andoils as well as gums, resins and waxes.Ether extraction is not usually done in thefeed analysis laboratory unless it isrequested. For this reason, the truemetabolisable energy of a feed may behigher than that reported from feed analysis

4

5

6

7

8

9

10

11

12

13

14

50 55 60 65 70 75 80

DIGESTIBILITY (%)

ME

(M

J/kg

DM

)

STRAW

HAY

PASPALUM

MAIZE SILAGE

PERMANENT PASTURE

SUB/PERSIAN CLOVER

GRAIN


1.11

available for digestion for every unit ofweight of the plant.

The digestible organic matter in the drymatter portion of a plant (DOMD) givesinformation about the stage of growth of aplant and can be used to predict theenergy the plant can supply (see Figure1.5). This figure can be given as apercentage.

determined by her age, live weight andbody surface area. A young heifer will eatmore than an adult cow as a percentage ofher body weight. A heifer will eat theequivalent of 2.3% of her body weightdaily, and an adult dry cow will eat theequivalent of 1.5%. As an example, a 300kg heifer can eat up to 7 kg dry matter. Anadult dry cow weighing 470 kg will eat asimilar amount.

The size of the rumen and its ability toexpand are limited by the size of the bodycavity where the rumen is situated.Distension of the rumen (‘gut fill’)depends on the rate of breakdown of feedroughage and the flow of small particlesfrom the rumen. Fat cows can have lowerintakes because of the effect of fatdeposits in the rumen and because theyhave lower energy requirements.

Physiological state

Milk production and stage of lactation candrive a cow’s intake. Before a cow calves,her intake is reduced because of thephysical restriction on the size of therumen by the developing foetus andbecause of the hormonal changesassociated with pregnancy.

After a cow calves, milk productionbegins; it reaches a peak yield at about 5–7 weeks after calving. The cow’smetabolism has to adapt to this demand onher body reserves; her intake is initiallydepressed, but it gradually increases untilshe reaches full appetite at 8–20 weeksafter calving.

This delay in reaching full appetitewhile the cow is producing peak yieldmeans that the cow is in a negative energybalance for this period. She cannot eatenough to supply the nutrients needed forbody maintenance, milk production andfertility. Weight loss usually occurs aftercalving.

The period between peak yield and fullappetite can be shortened if the cow’s

dry matter intake.Cow factors• size and age

• physiological state

• genetics

• disease

• social interaction

• heat stressFeed factors• digestibility

• nutrient supply

• palatability

Physical factors

• ability to harvest pasture• grazing time• intake per bite

• access to feed

We will consider these factors in greaterdetail.

Cow factors

Size and age

The maintenance requirement of a cow is

An important constraint of any dairy cowration is how much the cow can eat. If youformulate a ration to supply the nutrientsfor body maintenance, walking, pregnancyand milk yield you must be able to supplyit in amounts that the cow can eat.

A number of factors can affect a cow’s

How much feed can acow eat?


1.12

rumen is encouraged to expand beforecalving. Medium quality forage, at least11 mm in length, can provide the ‘scratchfactor’ needed to stimulate rumencapacity. The cereal component of thelactating diet, without the mineral mixesor buffers, can be fed in small amounts tothe cow for a month before calving toadapt the rumen microbes to the new diet.

Making changes to the early lactationdiet and calving your cows in goodcondition will benefit the early lactationcow. These factors will be discussed later.

The intake of a lactating cow can be30–60% greater than that of a non-lactating cow. There are numerous waysof predicting how much a cow will eat,but they are not as practical as an on-farmmethod. One simple rule of thumb forpredicting dry matter intake is that alactating cow will eat 2.5% of her liveweight if given low quality forage, 3% oflive weight if given a medium to goodquality diet and 3.5% of live weight ifgiven a high quality diet. Intakes as highas 4%, 4.5% and 5% of live weight canoccur on well balanced rations, especiallyin Jersey cattle.

Another quick rule of thumb fordetermining the intake of a lactating cowrequires you to know both her live weightand milk production. Her dry matterintake will be about (2.2 × live weight +20 × daily milk production in litres) /100.Example: What is the dry matter intake of a500 kg cow producing 20 litres of milk a day?

Dry matter intake = (2.2 × 500 + 20 × 20)/100

= (1100 + 400)/100

= 1500/100

= 15 kg DM.

Genetics

Dry matter intake can be influenced by thecow’s genetics. High breeding value cowscan eat more. In these cows, a 5% increasein intake can result in a disproportionateincrease in milk production (up to 30%).

Disease

A drop in appetite is a common signof many diseases. The first sign ofdisease can be decreased in milkproduction, because the cow hasreduced her feed intake.

Decreased intake can be causedby:

• metabolic changes in the cow as a resultof disease (for example, milk fever orlow blood calcium)

• physical changes in the rumenstimulating gut fill (for example, bloat)

• tumours and wounds in the mouth,pharynx or oesophagus

• diseases of the feet that physicallyrestrict the ability of the cow to graze.

Social interaction

Cows are very social animals and have anestablished hierarchy or ‘pecking order’within the herd. They form social groups,which may be family groups or theirheifer group. The introduction of newanimals to a herd can interfere with thisstructure until the hierarchy is re-established. Normal grazing patterns canbecome disrupted, resulting in lower feedintakes.

Mating groups can also form,especially in seasonally calving herds or inlarge herds where there is a significantnumber of cows on heat. Increasedwalking activity and behavioural changescan result in decreased feed intakes.

Heifers are most affected when they areintroduced to a dairy herd. Many heiferscan calve when they are only 75% of theirmature weight. Individual heifers are on thelowest rung of the pecking order, especiallyif they are small and can be bullied by themore dominant cows. Heifers aredisadvantaged at feed bunks if space islimited or at grazing if pasture feed islimited. Heifers grazed in groups separate


1.13

Table 1.2: Relationship of dry matter intake (DMI) to temperature

from the adult herd have both higher feedintakes and milk production.

Heat stress

Dairy cows originated from cool,temperature climates and preferenvironmental temperatures less than 25°C.Dry matter intake declines as the ambienttemperature increases, as table 1.2 shows.

Heat stress caused by high temperaturescan be increased if:

• there is poor access to cool, clean water

• there is high humidity—this prevents

the rumen and small intestine

• the proportions of the different nutrientsabsorbed

• the type and level of nutrients in thefeed.

Amino acids, from the breakdown ofprotein, stimulate intake. Volatile fattyacids, from the breakdown of fibre, caninhibit intake.

If the nitrogen content of the diet(crude protein content) meets the needs ofthe rumen microbes, intake will increasewith increasing digestibility, providing theproducts produced during digestion haveno adverse effect on the rumen or the cow.Example: Grain has high digestibility (about80%), but too much grain can cause acidconditions in the rumen which affect thedigestion of fibre and reduce total intake. In acidrumen conditions, there is less nitrogen made intomicrobial protein, leading to fewer amino acidspassing into the small intestine, reducing intake.

evaporation of heat; cows can show

If bloat occurs from eating too much grain or fromeating clovers or lucerne, the distension of therumen is sensed as ‘gut fill’ and intake reduces.

If two feeds have the samedigestibility, intake will increase withincreasing nitrogen (protein) intake. Feedswith low digestibility usually have a lownitrogen content. Increasing nitrogen inthe diet (but only up to 10–12% CP) willprovide greater nitrogen to the rumenmicrobes, allowing greater microbialgrowth and a greater ability to digest fibre.Intake increases in response to theimproved fibre digestion.Example: White clover – ryegrass pasture andryegrass pasture have the same high digestibility.The higher milk production seen on white clover

Mean day temperature ( EC) Mean night temperature ( EC) % reduction in DMI

25ñ30 20ñ25 10

30ñ35 20ñ30 20

35ñ40 25ñ30 30

heat stress at relatively low temperaturesif the humidity is high

• stock have to walk long distances

• stock do not have shade.

Feed factors

Digestibility

Dry matter intake increases by up to 65–80% with increasing digestibility of feed.Highly digestible feeds such as youngpastures have comparatively less structuralfibre (lignin) and are digested rapidly,allowing fast passage through the rumen.Gut fill is slower. Feeds with lowdigestibility (such as very mature pastures)limit intake by slowing the digestion andrumen passage and by accelerating gut fill.

Nutrient supply

Dry matter intake can be affected by:

• the quantities of nutrients absorbed by


1.14

ruminating.Farm management practices can

severely limit grazing time. Excessivetime spent in the milking yard andwalking to and from pasture at milkingtime, as well as poor access to water in thepaddock (requiring the cows to seek out awater trough in another place) will reducethe amount of time available to the cowfor grazing.

Intake per bite

The amount of pasture available candetermine how much a cow will eat at eachbite. A cow will eat her requirement inpasture if she is provided with twice thedry matter content of pasture she needs.Cows are selective grazers and will seekout the more digestible (and higherenergy) pasture in the longer pasture. Ifthe cow is offered less than this, she willstill eat the pasture but to a lower height.Her intake of the shorter pasture will beless. She will also be unable to selectpasture and will take in less digestibleparts of the pasture as well.

Access to feed

Cows should be allowed sufficient accessto feed. In a pasture, the presence ofweeds, dead plant material and manure patscan hinder the cows’ ability to graze.

At a feed bunk, there should besufficient space for each cow to eat without

– ryegrass pastures occurs because cows on thesepastures have a greater nitrogen intake, whichstimulates more microbial activity and a higherintake of pasture than occurs in cows grazed on

Ability to harvest pasture

The pasture intake of a cow can be definedby a number of physical factors:

• the time spent grazing (grazing time)

• the number of times the cow bites thepasture (rate of biting)

• the amount of pasture harvested at eachbite (intake per bite).

The total daily intake of pasture can becalculated by multiplying the grazing time(in minutes) by the rate of biting (bites perminute) by the intake per bite (kilogramsper bite).

Both the grazing time and the intakeper bite can be influenced by farmermanagement. The rate of biting is an

individual character of a cow.

Grazing time

When a cow is at pasture, she can beeither eating, ruminating (‘chewing hercud’) or resting. Cows graze mainly duringthe day, but night-time grazing increases ifthe day temperature is hot and humid. Theaverage time most cows can spend grazingis 7–8 hours. Another 8 hours may be spent

ryegrass alone.

Palatability

Palatability is the cow’s immediateresponse to the feed. The sight, smell,touch and taste of a feed can affectwhether a cow will eat or refuse a feed.The palatability of poor quality roughageshas a greater influence on intake than thepalatability of better quality forages.

Exposing a calf to a variety ofdifferent feeds can influence how itaccepts them in later life. One practicalway of doing this is to feed small amountsof the milkers’ ration to heifers.

Physical factors

competing with another cow. Access isvery important if most of the cows’ feedrequirement is fed at the bunk. Thereshould be at least 76 cm of feeding spacefor each cow. Headstalls or self-lockingstalls can allow cows adequate access tothe feed.

In herds feeding on partly or totallymixed rations, separating the herd intodifferent lactation group can benefit feedintake. Early lactation cows should haveunimpeded access to the bunk area, andthere should be sufficient space for every


1.15

cow. High-producing cows should bepresented with 10% more feed than theyrequire. For mid- to late lactation cows,space should be sufficient for only 50–75% of the group to be eating at any onetime.

The feed bunk should be cleaned outregularly, especially if feed with highmoisture content is fed. If these feeds areleft, moulds can build up and make thefeed unpalatable, even when new feed isadded.

Cattle fed in feedlots or on feed padshave a higher intake and milk productionthan pasture-fed cattle. Feedlot rationshave a higher dry matter content thanpastures, but the fibre content is usuallylower. Pastures with a high dry mattercontent also have a high fibre content,which limits feed intake (the digestibilityis lower). The rate of eating is faster in thefeedlot, because highly digestible feed ispresented to the cow—it doesn’t have tosearch for it in a pasture. Pasture-fedcattle have to walk longer distances whengrazing and use more energy in this activitythan feedlot cattle.

What nutrients does thecow need?

The nutrients needed by the cow (indescending importance) are water, energy,protein, fibre, macro minerals, microminerals and trace elements and vitamins.

Water

This is the most important nutrientrequired.

As saliva, water serves as an importantlubricant for swallowing and regurgitation.It is needed for the process of digestion andabsorption.

A lactating dairy cow needs a lot ofwater. Her body is 70–75% water, and

the milk she produces is over 85%water. Inadequate water will markedlyreduce milk production.

Usually a large proportion of the cow’swater intake is supplied by pasture. Whenyou supplement the cow’ diet with grainand hay, the need to supply extra waterincreases.

As the environmental temperature andthe cow’s milk yield increase, so does thewater requirement. Table 1.3 overleafshows the water intake of 600 kg Holsteincows at different temperatures and milkyields.How much water do your cows need? Use table1.3 as a guide. For example on a cool spring day(14°C), a 600 kg cow producing 30 litres a daywould need 103 litres of water. This would besupplied by water in the feed and drinking water.On a warm day in spring (24°C), the same cowwould need 133 litres of water from the feed and

the trough.

Dry cows and heifers need less water.For each kilogram of dry matter eaten, drycows and heifers need 5–7 litres of water,again depending on the environmentaltemperature. If a dry cow on a warm springday was eating 10 kg dry matter of grainand hay, then she would need about 70litres of drinking water at the trough.

In dry, hot weather the requirement forwater increases.

Energy

Energy is the next important nutrient and isthe chief limiting nutrient of most feeds(although it is not an actual substance likeprotein or minerals). When complexsubstances are broken down, energy isreleased and becomes available to theanimal. Carbohydrates such as sugars andstarches (non-structural carbohydrates) andcellulose, hemicellulose and lignin(structural carbohydrates or fibre) are themain energy sources in a cow’s diet. Fats(and to a lesser extent, protein) also provideenergy.


1.16

Table 1.3: Water intake of 600 kg Holstein cows at different temperatures and milkyields

Butyrate, another volatile fatty acidproduced in the rumen, is metabolised inthe liver to ketone bodies, the source ofenergy for fatty acid synthesis, skeletalmuscles and other body tissues. Ketonebodies are also produced when body fat ismobilised; they are used as an alternativeenergy source for the cow.

Fats are degraded in the rumen or, if ina protected form, pass to the intestine.Fats and oils are modified in the rumeninto saturated fat and absorbed. They areeither converted to a specific animal bodyfat (usually a triglyceride) or oxidised to agas if they are used as an energy source.Every lactation a cow goes through theprocess of accumulating and oxidising herbody fat.

If there is too much fat in a cow’s diet,fibre particles become coated with fat,making the surfaces difficult for microbialattack. Large amounts of fats can:

• depress the digestion of forages

• reduce the total feed intake

• lower the acetate to propionate ratio

• reduce the availability of calcium

• reduce the production of microbialprotein.

Cows can tolerate as much as 900 g offat a day in their diet (or 5–7% of theration’s total dry matter).

Protected fats escape microbialdigestion and can be used to overcome theproblem of increased breakdown of fat inthe rumen.

The structural and non-structuralcarbohydrates are converted to volatile fattyacids in the rumen. Acetic, propionic andbutyric acids (acetate, propionate andbutyrate) are the main volatile fatty acidsformed. The starches and pectens whichescape the rumen are converted to glucose inthe small intestine.

From The Nutrient Requirements of Livestock 1980

The proportion of volatile fatty acidsproduced depends on the original diet. Ifthe diet mainly contains structuralcarbohydrates (forages such as pasture andhay), the cellulose-digesting bacteria willpredominate and large quantities of acetatewill be produced. Acetate is theimmediate precursor of milk fat. Adeficiency of acetate can result in lowmilk fat percentage.

If the diet contains a large proportionof non-structural carbohydrates that arerapidly fermentable in the rumen (such ascereal grains) different bacteria will befavoured and a higher proportion ofpropionate will be produced. Propionateis converted in the liver to glucose.Glucose provides the energy for theproduction of lactose and synthesis ofprotein in milk. Lactose secretion is themain determinant of milk yield. Adeficiency of propionate can result indecreased milk yield and milkcomposition. Glucose provides theenergy needed for live weight gain. Ifthe cow has a deficiency of propionate shecan start to mobilise her own body tissueand lose weight.

Milk yield Environmental temperature ( EC)! 17 to 10 11 to 15 16 to 20 21 to 25

10 78 81 92 10520 88 92 104 11930 99 103 116 13340 109 113 128 147


1.17

Table 1.4: Energy needed formaintenance

Milk production

Energy is the most important nutrientdetermining milk production and milkprotein content. The amount of energyneeded depends on the number of litresproduced and the composition of the milk(milk fat and protein content). Table 1.6shows the amount of energy needed toproduce a litre of milk of a number ofdifferent compositions.

How much energy is needed bythe cow?

The metabolisable energy in a feed has tobe partitioned to the different bodyfunctions. In decreasing order ofimportance, energy will be partitioned tomaintenance, activity, pregnancy and milkproduction. If the energy in the feed isinsufficient for all body functions, milkproduction will be the first functionaffected.

Maintenance

How much energy does a cow need for herbody maintenance? Table 1.4 shows theenergy required daily for maintenance atdifferent live weights.

Activity

Cows need energy for walking. If thetopography of the dairy is flat, a cow will

need an extra 1 MJ of ME for eachkilometre walked. If the topography ishilly, more energy is used and a cow mayneed up to 5 MJ of ME per kilometre.

Pregnancy

What energy is required for a pregnantcow? The growing calf foetus is drawingall of its energy from its mother. In thelast four months of pregnancy, thedemands of the foetus must be allowed for.Table 1.5 shows the extra energy requiredby the cow for pregnancy.

Body condition

Cows gaining condition require extraenergy. For each kg of weight gained, anextra 34 MJ of ME is needed.

When a cow loses condition, energybecomes available to the cow. For each kgof weight lost, 28 MJ of ME is released forthe cow to use.

When we assess the condition of a cow,we use a system called ‘condition scoring’(see later). In Australia, the scoring system

we use ranges from 1–8 ‘conditionscores’, which are based on the degree offatness of the cow. For Holstein–Friesians,one condition score is equivalent to 42 kglive weight. For Jerseys, one conditionscore is about 26 kg live weight.

The energy needed for a Holstein–Friesian to gain one condition score is 42× 34 MJ of ME or 1428 MJ of ME. Thisenergy requirement is above that alreadyneeded for maintenance, lactation andpregnancy.

Rules of thumb

Is there another way of calculating cowenergy requirements?

There are a number of rules of thumb forquickly estimating how much energy a

Live weight (kg) Energy required(MJ of ME)

350 40

400 45

450 49

500 54

550 59

600 63

650 68

700 73


1.18

Table 1.5: Energy needed for pregnancy

Table 1.6: Energy needed to produce milk of various fat and protein compositions

requirement for the average cow will be134 MJ. This figure is a quick guide onlybut it can be useful to help you assess ifthe energy in the ration is adequate.

cow needs. One rough guide is to use themaintenance requirement which is typicalfor the herd, multiply the average milkproduction by 5 MJ, and add the twofigures together to get an estimate of thecow’s energy requirement. If the averagelive weight of a Holstein–Friesian herd is550 kg then (from table 1.4) themaintenance requirement is 59 MJ. If theaverage milk production is 15 litres, theenergy requirement for milk productionwill be 15 × 5 MJ or 75 MJ. So the total

Example: What is the energy requirement for a550 kg Holstein-Friesian cow, in late lactation,producing 15 litres of 3.2% protein, 3.8% fatmilk. The cow is 6 months pregnant. The dairy isabout 2 km flat walk from the day paddocks. Thenight paddocks are close to the dairy.

Use Table 1.4 to find the maintenance require-ment for a 550 cow: 59 MJ

Use Table 1.5 to find the energyneeded for pregnancy: 8 MJUse Table 1.6 to find the energy needed for each

litre of 3.2% protein and3.8% fat milk (5.2 MJ) and multiplythis value by the daily production of15 litres: 78 MJ

Calculate the energy needed for walking 4 kmper day (from the section on Activity, this will beabout 1 MJ per kilometre on flat land): 4 MJTotal energy needed: 149 MJ

How much energy is needed if the same cow is togain 0.5 kg live weight a day?

Month of pregnancy

6 7 8 9

Extra energyneeded (MJof ME perday)

7ñ8 10 14 19ñ20

Milk protein %

2.6 2.8 3.0 3.2 3.4 3.6

Milkfat %

Energy needed for milk productionMJME/day)

3.0 4.5 4.5 4.6 4.7 4.8 4.8

3.2 4.6 4.7 4.7 4.8 4.9 5.0

3.4 4.7 4.8 4.9 4.9 5.0 5.1

3.6 4.9 4.9 5.0 5.1 5.1 5.2

3.8 5.0 5.1 5.1 5.2 5.3 5.3

4.0 5.1 5.2 5.3 5.3 5.4 5.5

4.2 5.3 5.3 5.4 5.5 5.5 5.6

4.4 5.4 5.5 5.5 5.6 5.7 5.7

4.6 5.5 5.6 5.7 5.7 5.8 5.9

4.8 5.6 5.7 5.8 5.9 5.9 6.0

5.0 5.8 5.8 5.9 6.0 6.1 6.1

5.2 5.9 6.0 6.0 6.1 6.2 6.3


1.19

to supply the different essential aminoacids. Some feeds are unbalanced in theessential amino acids they supply. Theseunbalanced protein feeds (such as corngluten meal) are less efficient for thesynthesis of milk protein than balancedprotein sources (such as soybean meal). Rumen bacteria supplymost of the essential amino acidmethionine and rumen protozoa supplymost of the lysine. The overall diet canpreferentially encourage the growth of onespecies of microbe over another byproviding the substrate preferred by onegroup of microbes.

Too much protein in the diet can causeexcessive ammonia production in therumen, especially if the energy level in thediet is inadequate. If this is the case, therumen microbes don’t have enough energyto convert the ammonia to protein. Theammonia is absorbed from the rumen andenters the bloodstream and travels to theliver. The liver converts the ammonia tourea for excretion into the urine. Energy isneeded for this process. High bloodammonia levels is associated with reducedconception in cows (especially heifers).

If there is not enough protein in thediet or too much dietary energy comparedwith protein, microbial protein synthesisdecreases, resulting in a decrease in thetotal amount of protein available to thecow. The excess energy is used for puttingon body condition rather than for milkproduction.

If there is not enough energy in thediet, the dietary protein (especially UDP)can be used as an energy source, resultingin a poor milk response.

How much protein does a cowneed?

The amount of crude protein a cow needsvaries throughout lactation. The amount ofprotein required per energy unit in the diet

Protein

Proteins are made up of amino acids. Thecow needs 25 amino acids for bodymetabolism, growth, milk production andthe development of the foetus. Of theseamino acids, there are 10 which the cow

From the section on Body Condition, for everykilogram of weight gain the cow requires 34 MJ ofME. So to gain 0.5 kg per day, the cow will needan extra 17 MJ per day.

cannot make. These are the essentialamino acids, which must be supplied inthe diet or can be released after thedigestion of the rumen microbes (microbialprotein) in the small intestine.

The essential amino acids are:

• methionine

• lysine

• histidine

• threonine

• phenylalanine

• tryptophan

• arginine

• branched chain amino acids

Methionine and lysine are consideredthe main limiting amino acids in cows formilk production.

Amino acids can come from twosources:

• rumen microbes that pass out of therumen into the small intestine and aredigested.

• dietary protein that escapes the rumenand is digested in the small intestine(UDP).

Rumen microbes use the ammonia andnitrogen released from either dietaryprotein broken down in the rumen (RDP)or from non-protein nitrogen sources suchas urea to manufacture their own protein.RDP could be classified as the dietaryprotein needed by the rumen microbes, notthe cow.

Feeds and microbes vary in their ability


1.20

is much higher for milk production than formaintenance.

A range of crude protein percentages isgiven below. The high range value issuitable for high-producing cows andthose cows receiving significant amountsof supplements. The crude protein shouldcontain 30–35% of UDP.

• In early lactation, the diet shouldcontain 16–18 % crude protein. If thecow is producing over 16 litres a day,the crude protein percentage should beabout 18%, with a proportion of theprotein as UDP. According to Kellaway,the UDP requirement for cowsproducing over 16 litres per day is 93 gfor each litre over 16 litres.

Example: How much UDP does a cow producing30 litres in early lactation need?

The cow needs 93 × (30–16) g or 93 × 14 g ofUDP or 1302 g.

• In mid-lactation, the diet should contain

Table 1.7: Protein needed formaintenance

BF = butterfat

P = protein

Table 1.8: Protein needed for milkproduction

her back’—using her body energyreserves.

If the ration is deficient in feedsproviding sufficient energy formaintenance, growth and reproduction,especially in early lactation, the proteinsupplement will be used by the cow tomake up this shortfall in energy. Theminimum UDP and RDP requirements for

cows at different live weight and milkproduction are shown in table 1.9. Theassumptions used to calculate these figuresare:

• 8–10 g of microbial protein isproduced for every MJ of MEconsumed

• the ‘type’ cow used in the table is notpregnant and is producing milk with an

14–16% crude protein.

• In late lactation, the diet should contain12–14% crude protein.

• Dry cows should receive 10–12%crude protein.

• Springers may need 15% crude proteinif they are receiving a special ration.

For some rations you will need morespecific information on proteinrequirements. This is given in table 1.7 and1.8.

Do cows need UDP?

The answer to this question depends onyour farm management, the geneticpotential of your cows, and the feedmaking up the rest of the cows’ ration.Early lactation cows with a potential forhigh milk production will need UDP. Inearly lactation the cow’s appetite isdepressed and she may not be able toconsume enough nutrients for her potentialmilk production. She will be ‘milking off

Liveweight

(kg )

Crude protein needed formaintenance (g/day)

450 400

500 430

550 460

600 490

650 520

700 540

Crude protein (g) needed for each litre ofmilk

4.5% BF3.6% P

4.0% BF3.4% P

3.5% BF3.2% P

92 87 82


1.21

average composition of 4.0% BF and3.2% P

Table 1.9: Minimum UDP and RDP needs of cows for various levels of milkproduction at various weights, and energy (MJME)

used as the main determinant of fibre inthe diet. In Australia, NDF is not routinelymeasured in feeds and, at present, has tobe requested as an additional test.

The minimum ADF content in the totalration should range from 19 to 21%.

If NDF values are available for thediet, the following guidelines, althoughbased on US information, may be useful,especially if partial mixed or total mixedrations are fed (routinely or duringdrought).

The minimum forage dry matter intake(for hays, silages and pastures) is 2% liveweight. A 500 kg dairy cow should beeating a minimum of 10 kg DM of foragedaily.

The minimum crude fibre content is17% or NDF content of 25 to 30%. As arule, 75% of the NDF in the diet shouldcome from forages. If maize silage is fed,the NDF provided by forage should be30%.

The minimum amount of forage NDF is0.9% live weight. A 500 kg cow should getat least 4.5 kg NDF from the foragecomponent of the diet. The maximum NDF

Fibre

The source of the fibre and how it isdegraded in the rumen is important to thecow. Cellulose is the major energy sourcefor rumen microbes. Acetic acid is amajor breakdown product and is importantfor the production of milk and milk fatproduction. The importance of fibre hasbeen explained in the Energy sectionabove.

Not all fibre or fibre supplements arenutritional. (Some can be useful as bulk inhigh grain diets.) The ADF from matureforages, straws and cottonseed hulls ispoorly digested in the rumen because muchof it is indigestible.

How much fibre is needed bythe cow?

A minimum level of dietary fibre isneeded to promote rumen function andmaintain the milk fat test. The fibrecontent in a diet can be measured as crudefibre, NDF and ADF. In the USA, NDF is

Liveweight(kg)

Milk production (litres/day)

15 20 25 30 35

MJME

RDPUDP(g)

MJME

RDPUDP(g)

MJME

RDPUDP(g)

MJME

RDPUDP(g)

MJME

RDPUDP(g)

450 129 1084229

155 1302323

182 1529411

208 1747506

235 1974594

500 134 1126219

160 1344314

187 1571402

213 1789496

240 2016584

550 139 1168209

165 1386304

192 1613392

218 1831486

245 2058574

600 143 1201206

169 1420300

196 1646389

222 1865482

249 2092570


1.22

intake for feedlot cows is 1.25% liveweight or, for a 500 kg cow, 6.25 kg NDFdaily. NDF levels greater than this candecrease dry matter intake because ofaccelerated gut fill.

Fibre deficiency does not normallyoccur in pasture fed cattle. Lack of dietaryfibre, especially from forage sources, canoccur during droughts. Lush springpastures can be low in NDF. If thesepastures are fed with high levels of cerealgrains, the ration can lack adequate fibrefor maintaining milk fat percentage.

When low fibre diets are fed, buffersmay be needed in the ration, especially ifcereal grains are fed at greater than 4–5kg/cow/day.

The length of the fibre source fed is

ration is to calculate the percentage ofcows chewing their cud. If less than 50%of cows are chewing their cud at any time,then there is insufficient fibre in theration.

Minerals, trace elements andvitamins

These are essential nutrients needed fornormal metabolism and the function ofdifferent enzymes. The cow’s need forthese nutrients can vary with her liveweight, reproductive stage, level of milkproduction and other stresses. Forexample, heat stress increases the cow’srequirement for sodium and potassium.The Appendix lists the mineral andvitamin requirements for dairy cattle.

The mineral content of pastures andgrain feeds can vary throughout the year,depending on the soil type, irrigation andfertiliser use and the species of pasture orgrain grown.

The macrominerals required by thecow are calcium, phosphorus, sodium,magnesium, potassium and sulphur.Suboptimal intake of these minerals canresult in reduced milk production, reducedfertility and increased incidence ofmetabolic diseases.

Tropical pastures have a lower mineralcontent than temperate pastures. This ismainly true for sodium and phosphorus,and for calcium at certain growth stages(see the DairyLink Managing Pasturesmanual); also, different tropical pastureshave different levels. The magnesiumcontent in a pasture declines after potashand nitrogen fertilisers are used.

Cereal grains have low levels of mostminerals, especially calcium and sodium.Although cereal grains are believed to be agood source of phosphorus, thephosphorus content can vary dependingon the level of superphosphate use on thecrop.

important. The minimum length of forageshould be 2.5–3.0 cm. Hay should belonger than 4 cm to be effective asroughage. For silage chop, 15–20%should be 2.5–3.0 cm long, to provide aneffective fibre length of 8–10 mm. Ashorter chop length will allow betterpacking of the silage but will reduce thebuffering capacity. For maize silage,which contains substantial amounts ofgrain, a chop length of 11 mm or longercan provide effective roughage, althoughits buffering capacity can be less than thatof other silages.

You should calculate the forage toconcentrate ratio of the diet, as it can havean important impact on the milk fatpercentage. The length of the fibre canaffect this ratio. Long fibre stimulateschewing and salivation, resulting inincreased buffering by saliva. On pasture,the minimum forage to concentrate ratio is60:40. Lower ratios can result in milk fatdepression. Forage to concentrate rationsof 30:70 are possible for cattle on a totalmixed ration, providing the forage sourceis long chop hay.

One practical method of determining ifthere is sufficient effective fibre in the


1.23

The microminerals required by thecow are cobalt, copper, iodine, iron,manganese, molybdenum, selenium andzinc. The cow needs these minerals in traceamounts. Excessive amounts can be toxic.Deficiencies of these minerals can result ina poor response to infection, especially atcalving time. Using micro- mineralsupplements can give variable responses inmilk production. Supplementing with zinc

uptake of selenium even if the dietcontains adequate selenium.

Blood, urine and milk testing forminerals and vitamins is a better methodfor determining if the cow’s diet hasenough of these components. Ifdeficiencies are found, the mineral orvitamin can be added to the diet as apremix; added to the water supply;directly administered to the cow as aninjection or slow release bolus; orincluded in fertilisers for pastures orcrops.

What are the mineral andvitamin requirements of a cow?

The mineral and vitamin requirements of acow will vary with stage of lactation, theconditions under which she is housed orfed, environmental conditions, the qualityof the feed and other components of thefeed. Tables 1.10 and 1.11 arerecommendations for a 550 kg adultlactating cow producing 25 litres of milkand consuming 20 kg DM daily. Theyshould be used as a guide for the level ofminerals and vitamins that should besupplied in the feed.

If supplemental fat is fed, the calciumlevel may need to be increased to 0.95%and magnesium level increased to 0.30%.

In hot conditions, increased levels ofmagnesium (0.30%), potassium (1.30–1.50%) and sodium (0.50%) may be ofbenefit.

Table 1.11 shows the recommendedrequirements of the fat soluble vitamin A,D and E for a 550 kg cow producing 25litres per day, consuming 20 kg of drymatter daily. This table would be of use ifthe ration to be fed was a total mixed rationwhere the cows had no access to freshpasture. Vitamin K, another fat solublevitamin, is not required in the rationbecause it is synthesised in the rumen.

(as zinc methionine) reportedly improveshoof condition and hardness.

Many of the vitamins needed by thecow are supplied by green pasture. Whenpasture is limited or unavailable, or whenthe cows are being fed a ration consistingof cereal grains and conserved forage,vitamins A and E will need to be added tothe diet. Pastures containing high levels ofpolyunsaturated fatty acids (such as someclovers) or pastures that have beensprayed with oil or detergent to controlbloat can be deficient in vitamin E ortocopherol.

In the USA, vitamin A or betacarotene supplementation is required forudder health.

Analysing the diet for minerals andvitamins may not be enough to determine ifthe cow is receiving adequate amounts.There are many interactions amongdifferent mineral and vitamins in the cow,and a deficiency or excess of one mineralor vitamin can affect the function ofanother mineral and vitamin, even if thereare sufficient amounts in the body.Important interactions which can affectthe cow’s health are the relationshipsbetween calcium, magnesium and sodium;calcium and phosphorus; vitamin E,vitamin A and selenium; selenium andcopper; selenium and sulphur; and copperand molybdenum. Other components inthe diet can affect the levels of mineralsand vitamins in the cow. For example, adiet with inadequate protein can inhibit the


1.24

Table 1.10: Recommended mineral requirements for lactating dairy cattle

What feeds supply thesenutrients?

(Also see the DairyLink ManagingPastures manual.) Pasture supplies all ofthe nutrients required by the dairy cow.This statement might be surprising, butwithin limits it is true. Unfortunately, theideal pasture does not occur on all dairyfarms, nor does it exist throughout the year.The species of pasture, the season of the

year and how effectively the pasture isused affect the quality of nutrientssupplied to the cow. These conditions alsodetermine the quantity of pasture

available.Deficiencies of both the quality and

quantity of nutrients can occur in pasture,and you should know how and when touse supplements to correct thesedeficiencies. This is the basis of rationbalancing. This section examines the

Table 1.11: Recommended vitamin requirements for dairy cattle on total mixedrations

Mineral Recommended range inration

Maximum level inration

Estimatedamount/day

Macro-minerals

Calcium 0.43ñ0.77 2.0 116 g

Phosphorus 0.28ñ0.49 1.0 75 g

Magnesium 0.20ñ0.25 0.50 41 g

Potassium 0.90ñ1.00 3.0 184 g

Sodium 0.18 37 g

Chlorine 0.25 51 g

Sulphur 0.20ñ0.25 0.40 41 g

Micro-minerals

Cobalt 0.10 10 2 mg

Copper 10 100 204 mg

Iodine 0.60 50 12 mg

Iron 50 1000 1020 mg

Manganese 40 1000 816 mg

Selenium 0.10 3 mg

Zinc 40ñ60 500 816 mg

Ration levels

Vitamin Unit Recommended Maximum Estimated amount perday

A IU/kg 3260 - 4000 67,500 65250

D IU/kg 1000 10,000 20,250

E IU/kg 16 2025 315


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sorghum require fine grinding orhammer milling to release their starch.These two grains can also be cooked orsteam flaked.

By-product feeds

The production or manufacture of foodindustry commodities results in theproduction of waste that has littlecommercial value as a product. Dairiesoperating near areas where thesecommodities are produced can use thewaste or by-products from theproduction process as cattle feedingredients.

By-product feeds potentially containchemical residues. Any fruit andvegetable waste, fibre waste or seed fromcrops that have been treated withpesticides and herbicides, as well as‘new’ by-products not previously used incattle rations, should be tested forchemical residues. Never assume thatresidue testing has been performed ona feed. Always ask for residueinformation before you use a by-product feed.

Some by-product feeds might have ahigher energy content than that reportedon the feed analysis report. In the absenceof more complex and expensive analysis,the energy content of processed orpelleted feed is estimated from itsdigestibility and may be lower than thetrue energy content. Biscuit meal maycontain vegetable oil, a concentratedenergy source, as well as soluble sugars.Citrus pulp, although important as asource of fibre, is also a good source ofsoluble carbohydrates such as pectin.

Table 1.12 gives an analysis ofcommon energy feeds.

Fats and oils

Fats are a concentrated source of energythat can supply up to 35 MJME/kg DM.

feedstuffs that can supply differentcategories of nutrients.

Energy supplements

Cereals

Cereal grains and their by-products are themain sources of energy supplements. Thesesupplements can be fed whole, or as part ofa pelleted ration or ration mix.

As a rule, the dry matter and energycontents of most cereal grains are similar.The main exception is oats, which can belower in energy. By contrast, the proteincontent of grains can be very variable andcan range from less than 6% crude protein toover 16% crude protein. It is a good idea toanalyse cereal grains for crude proteincontent with each harvest shipment; neverassume that the next shipment will be similarto the last.

Cereal grains can be poor sources ofUDP (except for maize and sorghum).Grains are medium–high in phosphorus butlow in calcium.

A large percentage of whole grain canpass through to the faeces undigested,resulting in a loss of energy to the cow andloss of money to the farmer. Usually thecontact time between the rumen microbesand whole grain is too short for the grainseed coat to be broken down. Consequentlythe grain is poorly digested.

All grains, with the possible exception ofoats, benefit from some degree ofprocessing, because it makes the grain moreaccessible to digestion in the rumen. Thedegree of processing needed for a graindepends on its starch content. Withprocessing, the grain starch and solublecarbohydrates (NSC) become more availableto the rumen microbes and the rate ofrumen fermentation increases.

Wheat, barley and triticale should berolled or cracked. These grains contain thehighest amounts of starch. Corn and


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Fats are useful when the maximumamount of grain to forage ration is fed andthe diet still cannot meet the cow’s energyneeds. Milk responses to adding fat can beup to 3 litres, with an increase of 0.33% inmilk fat for each kilogram of fat eaten.

Fats that contain all the hydrogenatoms possible in their structure aresaturated fats. Those which contain lessthan the maximum amount of hydrogen areunsaturated fats.

Unsaturated fats are less stable, have alower melting point and are more prone togo rancid than saturated fats. Unsaturatedfats are found in oilseeds like soybean andcottonseed, and in the oils from theseseeds.

Saturated fats are found in tallow and

+ These are only the commonly used by-product feeds. Many by-products from a number ofagricultural industries can be used in cattle rations. The analysis for a number of the feeds is listed inseveral Australian publications, for example: the Funny Feeds booklet from NSW Agriculture; DairyCattle Production, Proceedings No.161, a 1991 publication available from the Post GraduateFoundation in Veterinary Science (phone 02 9264 2122); and the CAMDAIRY computer program.

Table 1.12: Analysis of some common energy feeds

fats of animal origin.High fat concentrations in the diet

(greater than 7% of the ration) can havenegative effects on rumen digestion andmicrobial growth. Feeding saturated fatsreduces the chance of these adverseeffects occurring. Vegetable oils should beavoided. Oilseeds such as soybeans andcottonseed can be used, because althoughthey contain unsaturated fat it is releasedslowly as the seeds are digested.

When you feed fat in a ration the fibrelevel of the ration should be high, with atleast 21% ADF, and an NDF of 28–32%.Calcium and magnesium levels should beraised because these minerals are lessavailable in the rumen, and since rumenbacteria do not benefit from the added

Feed DM% Metabolisable energy

MJME/kg DM

Crude protein (%)

NDF(%)

Average Range Average Range

Cereal grains

Barley 90 13 12ñ13 11 7ñ15 20

Wheat 90 13 12ñ13 12 9ñ16 12

Oats 90 11 9ñ12 9 6ñ13 26

Triticale 90 13 12ñ13 12 8ñ16 8

Maize 90 14 12ñ16 10 7ñ14 9

Sorghum 90 10 7ñ13 11 6ñ15 10

By-products+

Wheat pollard 90 11 17 36

Biscuit 84 11 10ñ13 8 4ñ12 18

Citrus pulp 18 10 8ñ11 8 6ñ11 23

Brewersí grain 25 10 9ñ11.5 23 21ñ26 42

Cereal grains

Sorghum

By-products+


1.27

energy as fat, the level of UDP in the rationshould also be increased. Fat should beadded gradually to the diet because it can

digestion. The end result is a build-up ofacid products in the rumen. The microbescapable of breaking down these acidproducts can be overwhelmed, so that theyslow down production of the by-productsneeded by other microbes (including thosethat digest fibre) for growth. As fibredigestion decreases the rumen functionslows, and the cow’s appetite drops.

This condition is called lactic acidosis.It can sometimes occur if cows are fed a‘slug’ of cereal grain in the bails duringmilking.

The risk of lactic acidosis can increasedramatically with some grains if they areprocessed. Milling or crushing can makethe grain starch more readily available fordigestion in the rumen. Wheat andtriticale have a high starch content andare highly rumen-digestible (about 60% isdigested in the rumen). The risk ofacidosis is greater using these grains, sothey should be coarsely processed.

The risk of acidosis is lower withwhole, uncracked barley and oats, whichhave a rumen digestibility is about 40%.Oats, which have a fibrous husk, stimulategreater saliva production and more naturalbuffering than other grains. Cracking thegrains increases digestibility.

The least risk occurs with sorghum andcorn. With these, about 30% of the grain

reduce palatability of the diet.Protected fats bypass the rumen and

are digested in the small intestine. Thesefats can be fed at higher levels withoutaffecting rumen digestion. However, theyare very expensive and should be fed onlyto high producing cows in earlylactation—these cows will be losing liveweight at a rate that can affect their futurefertility and health.

Most feeds contain some fat. Whenyou add fat to the diet, make sure youaccount for the fat in the entire ration. Ifthe ration is dusty, up to 1% of liquid fator oil can be added to settle the dustproviding the ration does not already ahigh percentage of fat.

Buffers

What are buffers?

Buffers are substances that help combatthe reduced pH that can occur in therumen from the formation of acids. Salivais a natural buffer that contains sodiumbicarbonate and sodium biphosphate. Feedadditives used as buffers include sodiumbicarbonate, magnesium oxide (causmag),sodium bentonite and limestone. Thesefeed additives vary widely in their abilityto buffer the rumen from very effective touseless.

Why do we need buffers?

Under normal conditions, saliva buffersthe formation of acid products in therumen. Saliva is produced in response to afibrous diet, which stimulates chewing.

When cows are fed large amounts ofcereal grains, the starch in the grain israpidly fermented to produce lactic acid.This acid has a greater ability to reducerumen pH than the volatile fatty acidsnormally released from fibre and protein

starch is digested in the rumen. When theyare fed whole or with little processing,many grains appear in the manure. Bothgrains can be finely processed to improvedigestion.

During drought or at other times whenthere is little pasture or conserved forage,saliva production and its buffering effectis reduced. Take care feeding cerealgrains, because the risk of rumen acidosiscan be high. Oats, which have a fibroushusk, may be the safest grain to feed if fedwhole.

Feeding buffers can reduce the risk ofacidosis in diets which are high grain/low


1.28

fibre or in which the grain portion of thediet is fed separately from the fibreportion (such as in the milking bails). Thefeed additives which have been used asbuffers, the recommended amounts to useand their effectiveness as buffers are listedin table 1.13.

Avoid sudden changes in dairy cattlerations. Such changes would includeintroducing cattle to grain or changingfrom one grain type to other (for example,oats to wheat). Rumen microbes should beallowed to adapt to the change in diet—otherwise milk production and cow healthwill suffer.

Table 1.14 gives a timetable forintroducing pasture-fed cattle to 3 kg/headof cereal grain supplements.

After about 3 weeks the cows will haveadapted to the grain diet and you will beable to stop adding the buffer.

Protein supplements

Protein can be provided by a number ofsupplements. Urea is regarded as a protein

Table 1.13: Some feed additives used as buffers

feed because it is a source of nitrogen formicrobial protein synthesis. It can be usedas a substitute for true protein in feedrations and is effective when fed with anadequate energy source. Table 1.15 tellsyou what’s in some common proteinsupplements.

The protein meals are usually a goodsource of UDP, although the quality canvary. The UDP levels in vegetable proteinmeals vary, but generally increase withprocessing. The manufacturing processes(usually heating and pressing) can vary,and the degree of protection of the proteinquality and degradability can also vary.Peanut meal has the same Pdg% assunflower and safflower meals – that is,10% greater than that of soyabean meal.Some manufacturers use formaldehyde toreduce the Pdg% of some vegetable meals.

The protein in grain legumes is readilydegradable. The percentage of protein inlegumes is similar to that in brewers’grain. The crude protein in brewers’ grainis approximately 30% UDP because of theheat generated by the fermentation process.

Additive % of totaldiet DM

kg/tonne ofgrain

Comment

Sodiumbicarbonate

1.5ñ2.0 15ñ20 Neutralises rumen acids.Unpalatable if fed at more than4% of ration. Can clump if feedis moist.

Magnesium oxide(causmag)

Up to 1 10 Neutralises rumen acids.Source of magnesium fortreatment of grass tetany. Donot use in springer or close-uprations.

Sodium bentonite Up to 4 Up to 40 Uncertain effectiveness asbuffer. Affects intake of grainby moderating grain digestionin rumen.

Calciumcarbonate(limestone)

1.5 15 Uncertain effectiveness as abuffer. Source of calcium.


1.29

Table 1.14: Suggested timetable forintroducing a cereal grain supplement

Table 1.15: Analysis of some common protein supplements

hays and silages provide fibre in the ration.These supplements are usually goodsources of energy and crude protein,although the quality can vary as it dependson the maturity of the pasture or crop.Table 1.16 shows what’s in some commonroughage supplements.

As roughages mature, the NDFpercentage increases but the metabolisableenergy and crude protein percentagesdecrease. Hay cut from late-floweringlucerne would be an excellent source oftotal fibre but would have a lower energylevel (8.2) and crude protein percentage(15%) than hay made from early-floweringlucerne (9.2 MJME; 22% CP).

The quality of silage is affected by howit is conserved and stored. When silage ismade, the carbohydrates in the originalforage are converted into fatty acids. Thedecreased pH stops bacterial growth, sothat the silage remains good until it is fed.You can find out how well the silage hasfermented by measuring (in addition to theusual dry matter, crude protein, energy andfibre content) the acidity (pH), the amounts

Because of the ‘mad cow’ scare inEurope there is a voluntary ban on the useof animal protein in cattle rations. A similarban has existed for the use of chicken littersince outbreaks of botulism occurred infeedlot cattle using this supplement as aprotein source.

Roughage supplements

Pastures and conserved forages such as

Day Grain percow(kg)

Buffer (forexample, sodium

bicarbonate)(% of ration)

1 0.5ñ1.0 0.5

3 1.0ñ1.5 0.5

5 1.5ñ2.0 1.0

7 2.0ñ2.5 1.5

9 2.5ñ3.5 2.0

Feed DM% MetabolisableEnergy

MJME/kg DM

Crude Protein(%)

NDF(%)


Urea 100 0 250 0

Grain legumes

Lupins 92 13 12ñ14 31 27ñ41 27

Cowpea 88 13 24 21ñ26 43ñ61

Faba bean 91 12.5 26 n/a

Protein meal

Soybean 88 13 51 15

Sunflower 93 10 33 40

Cottonseed 85 12 42 37ñ45 30

Urea

Grain legumes

Faba bean

Protein meal


1.30

and types of acids formed during theensilage process, the ammonia and theNSC. This analysis can be requested froma Feed Analysis Laboratory.

acids, extensive fermentation with mainlyacetic acid, high ammonia, low energy,unstable. Silages of this grading have beendamaged through poor storage. Theoriginal pasture or crop may have beentoo wet, or did not contain enoughcarbohydrate to produce enough acid, andtoo much of the protein was broken downto ammonia. Cows that eat it have a lowdry matter intake because of its slowdigestibility.

Grade VI. Highly acid silage withboth lactic and volatile fatty acids and lowprotein breakdown. Reduces the cows’ dry

high energy, low pH (below 4.0). Reducesthe cows’ dry matter intake unless fedwith a buffer such as sodium bicarbonate.

Grade V. Contains highly volatile fatty

In the UK, silages are graded accordingto the composition:

Grade I. High sugar levels with somefermentation acids. Mineral acids areadded during ensilage.

Grade II. Low-acid silage with highdry matter content. Wilted pasture isensiled without being damaged by rain orother mishap. Animals usually performwell on these silages.

Grade III. Normal. Contains mainlylactic acid with some acetic acid. Theammonia level is below 10% of the totalnitrogen. Animal performance will reflectthe chemical composition of the silageand will not be affected by thefermentation products.

Grade IV. High lactic acid content,

Table 1.16: Analysis of some common roughage supplements

* ranges reflect early-late maturing of harvest

matter intake.

Minerals

The mineral content of a feed orsupplement is of little value to formulatinga ration unless the availability, ordigestibility, of the mineral is known.Biological availability tells how a mineralis digested and used by the animal. As theavailability of a mineral decreases, theamount of the mineral needed to meet the

Feed DM%

Metabolisable energyMJME/kg DM

Crude protein(%)

NDF*(%)


Hays

Lucerne hay 85 8.7 8.2ñ9.2 20 15ñ22 49ñ57

Clover hay 88 9.3 8.2ñ10.2 16 13ñ18 40ñ43

Ryegrass/clover hay 84 9 12 49ñ67

Sorghum hay 89 8 8 68

Silages

Maize silage 30 9.9 8 48

Ryegrass/cloversilage

24 9 13 39ñ58

Sorghum silage 30 8 9 68

Hays

Sorghum hay

Silages


1.31

cow’s requirement will increase. Theavailability is also affected by the level ofother minerals in the diet and the age of thestock. Table 1.17 gives the relativeavailabilities of some calcium, phosphorus,magnesium and sulphur sources for thecow.

Getting value from feedanalysis

How accurate are the results from yourfeed analysis laboratory? The answer isthat they are only as accurate as the sampleyou sent in for testing.

When you are sending in a feed samplefor analysis, follow these rules to makesure the results will be accurate:

• Make sure the sample represents thefeed you want to test.

If a sample is taken from a pasturethat contains a mix of different species,it should reflect this mix properly. Forexample, if the pasture is ryegrass with30% clover, the sample should containthis same mix.

If you’re taking a sample from hay orsilage, use a corer. If you want to test ahay shipment, take samples from at least20 bales to get an average result. Ifyou’re testing silage, take a sample fromthe centre of a round bale, about 10samples from the face of the pit, or asample from the silage before it is fedout. Don’t take a sample from theoutside edge of the bale or pit, as thispart has been exposed to air and is

Note: Bone meal is not recommended because of concerns over ‘mad cow disease’.

Table 1.17: Relative availabilities of calcium, phosphorus, magnesium and sulphurfrom common feed sources

Source

Relativeavailability

Calcium Phosphorus Magnesium Sulphur

High Calciumchloride

Monocalciumphosphate

Magnesiumoxide

Calciumsulphate

Monocalciumphosphate

Monosodiumphosphate

Magnesiumsulphate

Sodiumsulphate

Dicalciumphosphate

Ammoniumphosphate

Magnesiumcarbonate

Potassiumsulphate

Dicalciumphosphate

Magnesiumsulphate

Medium Calciumcarbonate

Sodium tri-polyphosphate

Magnesiumchloride

Limestone Defluorinatedphosphate

Low Forages Low fluorinerock phosphate

Dolomiticlimestone

Elementalsulphur

Soft rockphosphate

Forages, grains

Source

Relativeavailability


1.32

usually drier or has deteriorated inquality.

Sample cereal grains and feed mixes

residues in the cow, the calf or themilk. These components are usuallycontaminants such as pesticides,herbicides, insecticides and otherchemicals used in the production orpreservation of the feed. Any feedsource can contain these contaminantsand they should be tested for.

Some examples of how youcan benefit from feed analysis

The following examples are based on theinformation presented in this section. Usethem as a guide to determining thenutrient content of the feed you are givingyour cows.

from the storage bin, not from the feedbails.

• Send the sample to the laboratory ina sealed plastic bag.

If the sample is dry (such as a cerealgrain) this will stop it being lost duringtransport to the laboratory.

If the sample is moist (such aspasture) try to remove as much of theair as possible from the bag before it issealed. This will stop the sample dryingout and reduce the risk of mouldsdeveloping.

If the sample is silage, freeze itbefore transport and send it to thelaboratory as soon as possible. Silagecontains many volatile components andcan deteriorate rapidly when exposed toair.

• Send the sample to the laboratoryimmediately.

• Select the best test for your type offeed.

There are several ways the samplecan be analysed at the laboratory. TheNear InfraRed (NIR)spectrophotometry method canmeasure the important components ofcommon feeds such as single foragecrops or pastures and single cerealgrains. If you want tests on mixedfeeds (such as grain mix and pasturemix) or unusual feedstuffs (such as abiscuit meal or silage), or if you want awider than normal range of componentsmeasured, then the feed should beanalysed by laboratory methods called‘wet chemistry’.

Feeds may be sent to other specialistlaboratories for analysis for differentminerals, vitamins, toxins and moulds.

Feeds can contain other componentsthat have no feed value but can leave

Example 1: A cow eats 85 kg of ryegrass pasturea day. A sample of pasture is analysed and thefollowing results obtained:

Dry matter 20%

Nitrogen 3.52%

Crude protein 22%

ADF 24%

Energy 11 MJ of ME

How much crude protein and energy is the cowconsuming each day?

Step 1: Calculate the amount of dry matterconsumed. The cow is eating 85 kg of pasture ofwhich 20% is dry matter. The remainder is water.

Multiply 85 by 20 and divide by 100 to get thedry matter content of 17 kg:

85 kg× 20/100 = 17 kg

Step 2: Each kg of dry matter contains 22% ofcrude protein. Remember crude protein iscalculated by multiplying the nitrogen value by6.25.

Multiply 17 kg by 22 and divide by 100 to getthe total amount of crude protein of 3.74 kg:

17 kg × 22/100 = 3.74 kg

Step 3: Each kg of dry matter contains 11 MJ/ME.

Multiply 17 by 11 to get the total energy of thediet of 187 MJME:

17 × 11 MJME = 187 MJME

Example 2: We have two groups of cows. Each isbeing fed 22 kg of brewers’ grain, but the grain is


1.33

each 1100 kg of bail feed (1000 kg of barley and100 kg of cottonseed meal).

The percentage of cottonseed meal in the bailfeed is 100 divided by 1100 multiplied by 100, togive 9.1%.

100/1100 × 100 = 9.1%We are also estimating the amount of pasture

eaten by the cow. She may be eating more than 14kg dry matter or she may eat less. We have no wayof accurately measuring how much she is eating.We know that the entire herd has consumed anaverage of 14 kg dry matter so we will use theaverage figure for our cow.

from two different shipments, A and B. The cowsbeing fed brewers’ grain from shipment A areproducing 2 litres more milk than those being fed

from shipment B. What is the problem?Feed samples from both shipments were sent for

feed analysis. Both shipments have a crudeprotein percentage of 18% and an energy contentof 10 MJME. Shipment A has a dry matter contentof 40% and shipment B has a dry matter contentof 35%.

The cows fed brewers’ grain from shipment Awill get (40/100 (DM%) × 18/100 (protein %) ×22 kg) or 1.58 kg of crude protein and (40/100(DM%) × 10 MJME (energy) × 22 kg) or 88MJME of energy. Those cows fed from shipmentB will get (35/100 (DM%) × 18/100 (protein%) ×22 kg) or 1.39 kg of crude protein and (35/100(DM%) × 10 MJME (energy) × 22 kg) or 77MJME of energy.

The lowered milk production in the cows beingfed from shipment B is probably due to the lowertotal protein and energy intake.

Example 3: A cow is consuming 3 kg of a barley– cottonseed meal mix in the bails and is grazingryegrass pastures. You have used a pasture meterto determine that the average intake of ryegrasspasture per cow is 14 kg dry matter.

The bail mix consists of two 50 kg bags ofcottonseed meal to each tonne of barley.

Feed analysis for the barley and cottonseed mealfollows:

Barley Cottonseed meal

Dry matter 90% 90%

CP 11% 44%ADF 7% 19%

Energy 13 MJ 11 MJThe analysis of the ryegrass is the same as in

example 1.Estimate how much crude protein and energy

the cow is consuming.In this example we need to do some calculations

on how much barley and cottonseed meal the cowcould be getting in the bail feed. We areestimating what this cow is eating in the bails.We do not know for certain what the actualcontent of the bail feed is, even though we knowthe ingredients. We are assuming that the bail feedis mixed properly, distributing the cottonseedmeal throughout the barley grain, and that thefeed droppers have delivered 3 kg of this mix tothe cow.

Step 1: Calculate the amount of cottonseed mealin the total bail feed. Two 50 kg bags ofcottonseed meal are added per tonne of barley.Therefore there are 100 kg of cottonseed meal in

Step 2: Calculate the total dry matter consumedby the cow.

The bail feed contains 9.1% cottonseed meal.The cow is consuming 3 kg of the feed. The drymatter content of cottonseed meal is 90%.

Multiply 3 kg by 9.1 and divide by 100.Multiply this answer by 90 and divide by 100 toestimate the cottonseed dry matter intake of 0.25kg:

3 kg × 9.1/100 × 90/100 = 0.25 kgThe bail feed contains (100–9.1) or 91.9%

barley. The cow is consuming 3 kg of the feed.The dry matter content of barley is 90%.

Multiply 3 kg by 91.9 and divide by 100.Multiply this answer by 90 and divide by 100 toestimate the barley dry matter of 2.48 kg:

3 kg × 91.9/100 × 90/100 = 2.48 kgThe total dry matter consumed by the cow is

16.73 kg (0.25 [cottonseed meal] + 2.48 [barley] +14.0 [pasture]).

Step 3: Calculate the total crude proteinconsumed by the cow.

We need to calculate the amount of crudeprotein each component contributes to the ration.

(a) Each kg dry matter of cottonseed mealcontains 44% crude protein.

Multiply 0.25 kg by 44 and divide by 100 to getthe cottonseed crude protein contribution of 0.11kg:

0.25 kg × 44/100 = 0.11 kg(b) Each kg dry matter of barley contains 11%

crude protein.Multiply 2.48 kg by 11 and divide by 100 to get

the barley crude protein contribution of 0.27kg:2.48 × 11/100 = 0.27 kg

(c) Each kg dry matter of ryegrass pasturecontains 22% of crude protein.

Multiply 14 kg by 22 and divide by 100 to getthe ryegrass crude protein contribution of 3.08kg:

14 kg × 22/100 = 3.08 kgThe total crude protein content of the diet is

3.46 kg (0.11 [cottonseed meal] + 0.27 [barley] +3.08 [pasture])


1.34

Step 4: Calculate the total energy in the dietconsumed by the cow.

We need to calculate the amount of energy eachcomponent contributes to the ration.

(a) Each kg dry matter of cottonseed mealcontains 11 MJ.

Multiply 0.25 kg by 11 to get the cottonseedenergy contribution of 2.75 MJ:

0.25 kg × 11 = 2.75 MJ(b) Each kg dry matter of barley contains 13

MJ.Multiply 2.48 kg by 13 to get the barley energy

contribution of 32.24 MJ:2.48 × 13 = 32.24 MJ

(c) Each kg dry matter of ryegrass pasturecontains 11 MJ.

Multiply 14 kg by 11 to get the ryegrass energy

of 154 MJ:14 kg × 11 = 154 MJ

The total energy content of the diet is 189 MJ(2.75 [cottonseed meal] + 32.24 [barley] + 154[pasture]).


2.1

Costing pasture & supplements


Pasture is the most important source offeed for dairy cattle in Australia. It cansupply a well balanced diet verycheaply—this is important if we are tomaintain our dairy industry’scompetitiveness in the world exportmarket.

But there are occasions when pasturealone is not the best feed for the cow.

In this section you will gain a greaterknowledge of:

• when and why pasture may not beadequate for feeding cows

• how much pasture can cost as a feed

• when and why feed supplements areused

• how to feed supplements

• how to use cost to comparesupplements.


To understand this section you will needsome knowledge about pasture types andhow they are established and used. Thisinformation is given in the DairyLinkmanuals Establishing Pastures andManaging Pastures.

Why not feed pasturealone?

Pasture is recognised as the cheapestsource of feed for dairy cattle. It does notneed to be harvested or stored and itdoesn’t need special facilities for feedingout. The cow harvests what she requires.But you must still make sure that thequality and quantity of the pastureavailable is adequate for your cows’needs.

Table 2.1: Changes in protein and energy with maturity and after grazing in aryegrass pasture (from Feed Evaluation Service Database)

The quality of pasture can vary fromexcellent to very poor, depending upon thespecies of pasture and its maturity. Tables2.1 and 2.2 compare different pasturespecies at different stages of growth.

Table 2.1 shows that the younger thepasture, the greater the energy and proteincontent and the overall digestibility. Soshould we feed cows only young pasture?

The answer is both yes and no. Itdepends upon the physiological state ofthe cow, her genetic potential for milkproduction and the nutrient balance in thepasture.

How good is pasture as a feed?

Stage of maturity Dry matter(%)

Metabolisableenergy

MJME/kg DM

Crude protein(%)

Young ñ early vegetative 10 11.2 24.6

Flowering 22 9.1 13.8

Regrowth (32ñ38 days) 14 10.9 21.8


2.2

Table 2.2: Changes in energy, protein and yield in an oat crop as it matures (fromCole VG, 1981, Guide to Fodder Crops for Livestock, Macarthur Press

Energy

Young lush pasture has a very low drymatter content. Remember that allnutrients in a feed are compared with thedry matter content. In young ryegrass, theenergy content is 11 MJ of ME per kg drymatter and the dry matter percentage isonly 10%. The digestibility of the pastureis high (80%) and the fibre content (ADF)is low.

If we are feeding the cow from theexample on page 1.18 (a 550 kg cow inlate lactation producing 15 litres per day),you will remember that she required 149MJ of ME a day. Her total dry matterintake (using the ‘rule of thumb’ equationon page 1.12) is 15 kg. At full appetite, thecow could eat 132 MJME from the lushryegrass pasture (15 kg × 11 MJ × 0.80[digestibility]), which is 17 MJ less than theenergy she requires.

This intake is equivalent to 150 kg offresh feed, of which 135 kg is water(10% dry matter means 90% watercontent). The cow would need a largenumber of hours grazing to take in thismuch fresh feed. If her grazing time wasrestricted, the energy deficit in the dietwould be greater.

If the same cow was in early lactation,with the potential to produce a peak milkyield of 40 litres, her potential dry matterintake would be 20 kg. Her total energyrequirement would be 270 MJ of ME aday.

At full appetite, this cow would be able

to consume only 176 MJME from thepasture.

Pasture that has enough energy for alate lactation cow can be unsuitable for anearly lactationcow producing 40 litres.However, this pasture may be able toprovide enough energy for an earlylactation cow with lower production or alate lactation cow.

Energy is only one nutrient we need toconsider in pasture. Even if enoughenergy is provided, deficiencies orexcesses of other nutrients can occur. Theprotein, fibre, macro mineral, micromineral and trace element contents nowneed to be considered.

Protein

Lush spring pastures (especially ryegrassand white clover) are usually high inprotein (mainly RDP). Pasture is not agood source of UDP. Only 10% UDP isprovided by most pastures. High-producing early lactation cows require atleast 30% UDP in their diet.

If the RDP content of the pasture is toohigh, an excessive amount of ammoniawill be absorbed from the rumen; this willneed to be converted to urea before it isexcreted in the urine. High blood levels ofboth ammonia and urea can reducefertility. There is some debate about whatpasture protein percentage or blood urealevel is damaging to the cow and herfertility. New Zealand cattle reportedlycan eat diets with RDP levels much higher

Stage of maturity Metabolisable energyMJME/kg DM

Crude protein(%)

Yieldkg DM/ha

Immature 12.8 28 2000

Early bloom 12.0 15 6000

Full bloom 8.3 10 8750


2.3

than those said to cause fertility problemsin American dairy cattle and have no illeffects.

Kellaway suggests that RDP intakesgreater than 11 g/MJME can lead tofertility problems.

the pasture. There is a slower passage ofthe feed through the rumen. Cows mayreach ‘gut fill’ before they can take inenough energy.

Minerals and trace elements

As indicated in the DairyLink ManagingPastures manual, the mineral content ofpastures can vary considerably.

Most minerals and trace elements aresupplied to the plant from the soil. Somesoils can be naturally deficient or canbecome depleted after long-term croppingor grazing. Fertilisers can replace somelost minerals, such as phosphorus,potassium and sulphur. The change in soilpH after fertiliser use can make traceelements such as selenium and cobaltunavailable to the plant. Irrigation andheavy rainfall can leach minerals from thesoil or can change the oxygen content ofthe soil, and this can change minerals intoforms that are unavailable to the plant.

Legumes are usually low in traceelements such as selenium, and grassescan be low in copper. Pasture species suchas kikuyu can be deficient in calcium andsodium but can contain very high levels ofpotassium.

Summary

Pasture, although a very good feed source,may not be an adequate feed for highlevels of milk production, weight gain,fertility and overall health throughout theyear. Supplements can replace theshortfall in pasture quality and quantity oroptimise rumen microbial activity duringtimes of excess nutrients.

Substitution

Cows will reduce their intake of pasture ifthey are offered a dietary supplement. Therate of substitution is the reduction inpasture intake divided by the weight of the

Example: A ryegrass pasture has a crude proteincontent of 31%, energy level of 12 MJME and drymatter content of 15%. Could this pasture cause a

fertility problem?In most pastures 90% of the protein is RDP. The

amount of crude protein for each kg of dry matteris 31 × 15 = 465 g protein/kg DM, of which 90%or 465 × 90/100 = 418.5 g is RDP.

If we divide the amount of RDP by the energycontent of the pasture (418.5/12), we get 35 g/MJME, which more than three times over thethreshold suggested by Kelloway. This pasture

may be the cause of fertility problems in the herd.

Fibre

The proportion of ADF in the NDFfraction of a plant increases as a plantmatures—the proportion of indigestiblecomponents in the plant increases.

Some pastures have higher levels ofNDF at all stages of growth. Kikuyu andpaspalum have considerably higher NDFlevels than ryegrass and clover.

In young pasture, the low NDF % isaccompanied by high crude proteinpercentages. Since the digestibility of thepasture is high, there will be a rapidpassage of feed through the rumen. Excessprotein will enter the rumen and bedegraded. The nitrogen is converted toammonia for excretion into thebloodstream and processing into urea. Theeffect of high ammonia levels wasdiscussed in Section 1.

Mature pastures contain higherpercentages of NDF with a higherproportion of indigestible components.The energy content of these pastures islower because the indigestible fibre canprevent the rumen microbes from reachingand digesting the starches and sugars of


2.4

supplement given. For example, if hay isgiven to a grazing cow, the cow’s intake ofpasture will decrease by the same amountof hay consumed. The substitution rate ofhay is 1.0.

When concentrates are fed, the rate ofsubstitution can vary depending on theamount and quality of the pasture fed, thequantity of the supplement eaten and thedegree of processing of the supplement.

Figure 2.1 shows the effect of theavailability and digestibility of the pastureon the substitution rate of a concentratewith a digestibility of 0.8.

The substitution rate is less when cowsare grazing a pasture of low digestibilityor when the availability of pasture is low.The rate of substitution increases with theproportion of concentrate in the diet from0.6 (if feeding less than 25% of the diet asconcentrate) to about 1.2 (if more than50% concentrates are fed). Substitution ishigher if the concentrates are rapidlyfermented (for example, wheat starch)than if they are slowly fermented (wholeoats).

Figure 2.1: Predicted substitution rates for a supplement of 80% digestibility onpastures averaging 70% (heavy line) and 50% (light line) (from Kellaway & Porta1993)

Example: Here is an example of the cost of bothdryland and irrigated pasture production for 100

milkers on a 74 ha farm (adapted from Kellaway)

Item $/ha/yearSeed, fertilisers andchemicals 194(Single superphosphatePerennial ryegrassWhite cloverGreentop (20:5:0)NitramMuriate of potashAnnual ryegrassSprayseed®)Tractor depreciation 28Tractor maintenance and fuel 25Machinery depreciation and repairs 82Fencing depreciation and repair 12Labour 242Rates 40Dryland total 623

Extra costs for irrigation:Irrigation electricity 94Irrigation depreciation and repairs 74Irrigation pump deprecation 4Irrigation fittings 6Irrigation total 800

How much does pasturecost?


2.5

South Coast of NSW, Kellaway found thatpasture use ranged from 11% to 40% atdifferent times of the year. The cost ofpasture at low utilisation rates approachesthe cost of some bought supplements on adry matter basis!

(Cost of buying water for irrigation not included.)

Assume that the pasture production for bothdryland and irrigated farms is 15 tonnes DM perhectare. Then the dryland cost of pasture is $41per tonne DM and the irrigated cost of pasture is

$53 per tonne DM.

This example estimates the cost ofgrowing pasture, both for dryland andirrigated pastures. This cost is theminimum for each kg of pasture dry matterproduced. Unfortunately, a cow does noteat all of this dry matter. It will not eat thepasture to the ground.

As outlined in the Managing PasturesDairyLink manual, the persistence of apasture is affected by the dry matter leftafter grazing (the residual). For example, ifcows are grazing a ryegrass pasture in agood season (when there is adequaterainfall or there is access to irrigation), thenthe pasture can be grazed down to 5 cm or1000–1500 kg dry matter without anyadverse effect on future production. In adry season, a greater amount of pastureshould be left—about 7–9 cm or 2000 kgdry matter.

When you are calculating the cost ofpasture, make sure you assess the amountof pasture left behind after the cows havegrazed. This value can help you calculatethe approximate use of the pasture, whichis:

Why use supplements?

You can get many benefits from usingsupplements. They can be categorised intotwo classes: short-term and long-term.

Short-term benefits

Increased milk production and quality

The responses in milk production tofeeding supplements normally occur with 1to 3 weeks, depending on a number ofinterrelated factors (such as the stage oflactation, degree and level ofunderfeeding, genetic potential andweight).

Problems with low milk fatpercentages or sudden falls in milk proteincan be corrected by adding the correctsupplement, depending on the severity ofthe underfeeding. Responses are quitevariable.

Milk response to supplementation isgreater during early lactation. On mostfarms, the increased milk productionbenefit received from feeding supplementsto early lactation cows compensates for thecost of feeding the supplements. Long-termresponses to concentrates average 1.2 L ofmilk per kg of concentrate. Short-termresponses range from 0 to 0.5 L of milk perkg of concentrate.

At times of low pasture growth,supplements like cereal grains can helpmaintain milk production until pasturegrowth improves or until a cheaper sourceof supplement (such as high quality foragecrops) becomes available.

Percentage of pasture used

= Total dry matter yield – residual dry matter .

Total dry matter yield

Once you have calculated the totalpercentage used you can then work out thetotal cost of the pasture as a feed.

If the total use of the pasture is 50%and the cost of growing the pasture is $67per tonne DM, then the cost of the pastureas feed is $124 per tonne DM. The poorerthe use of the pasture, the more expensivethe pasture costs as a feed. In a study ofthree dairy farms in the Sydney basin and


2.6

Supplying the nutrients missing inpasture

Pasture can be inadequate in energy,protein, minerals and trace elements atdifferent periods of the year. Milkproduction can suffer if the right mix ofnutrients is not present in the ration.

Providing sufficient nutrients to earlylactation cows

After calving, the cow’s rumen capacity istoo small in relation to the dry matter intakeneeded to reach her potential milkproduction. The cow needs a nutrientdense ration where the quantities of allthe nutrients such as dry matter, energy,protein and fibre are increased in the rationto compensate for her lower appetite.Rations with high amounts of water (lowDM %) fill up the rumen before the cowcan get enough nutrients for her energyrequirements.

Supplementing pasture with energyfeeds such as cereal grains can provide aration that is more energy dense. Othersupplements may be needed to meet theprotein, mineral and trace elementrequirements.

After the cow has reached full appetiteand her milk production starts to decline(that is, after peak lactation), the nutrientconcentration of the feed can be reduced.Most cows will be able to get their nutrientrequirements from pasture, although high-producing cows will still need somesupplementation.

Long-term benefits

Better pasture use

The DairyLink Managing Pastures manualoutlines the best ways to manage pastures.

High pasture utilisation, althoughensuring pasture quality, can causeinsufficient pasture intake for highproducing cows. Supplements can make upthe shortfall in dry matter intake.

Supplements can be used to reduceovergrazing and meet shortfalls whenpasture growth is slow.

Improved body condition of the cows

Lactation length, persistence of the peakmilk yield and fertility are all influenced bythe cow’s overall nutrition.

The cow’s body reserves at about thetime of calving can influence the amount ofmilk produced at the time of peak yield.The better the condition of the cow(providing she is not too fat), the greaterthe chance of her reaching her expectedpeak milk production.

Cows in good body condition aftercalving start their heat cycling andconceive in a shorter time than cows inpoorer body condition. Fertility is thereforeinfluenced by how the cow was fed duringlate lactation, during the dry period and theperiod after calving when most cows are innegative energy balance.

Pasture shortages at certain times of theyear may prevent weight gains in lactatingcows and dry stock.

Reduced rate of involuntary culling

Voluntary culling is a management decisionto cull cows because they are unsuitable inmilk production, milk composition or bodyconformation. Voluntary culling is done toimprove genetics and overall milkproduction.

Involuntary culling means the culling ofa cow because of disease or poorproduction. The cow ‘selects’ herself to beculled. Cows of high genetic merit may bewasted through involuntary culling because


2.7

they have a condition that may not haveoccurred if feeding was adequate.

Increased farm profitability

The use of cost-effective supplementscan increase milk production and increaseyour profits. Other long-term economicbenefits are:

• better fertility (fewer services for eachsuccessful conception, reduced overallsemen cost, reduced cost of treatmentof non-cycling cows)

• reduced involuntary culling costs (thecost of raising an increased number ofreplacement heifers minus the incomefrom the sale of the culled cows)

• reduced costs of disease treatment,especially of cows at calving and earlylactation. The metabolic diseases thatoccur in early lactation are usually theresult of inadequate or imbalancednutrition.

How do I use supplementsensibly?

Basic requirements for feedingsupplements

Feeding a supplement involves moredecisions than choosing a feed. This

section deals with the practical aspects offeeding supplements.

Storage

All supplements must be stored before theyare used. It is not feasible or economic totransport supplements to the farm onlywhen they are needed.

Store the supplements so that they don’tdeteriorate. If a supplement is exposed tomoisture or excessive heat and humidity (orair if it is stored as silage), moulds andfungi can grow. These can cause the

nutrient content to drop and create healthproblems in the cattle being fed thesupplement.

Silos, feed sheds, feed bunks, silage pitsand plastic-wrapped feed bales can providesuitable storage for different classes offeed.

Feeding-out

Dairy bails. Many dairies feedsupplements in the dairy bails. If you arefeeding in the dairy shed, the minimumrequirements are a feeding trough and ameans of transferring the feed to thetrough. The equipment required to do thiscan range from a bucket to different typesof manual and automatic feed dispensers,feed augers for transferring the feed fromthe storage to the dispensers, or fullycomputerised feeding systems.

Advantage of feeding in the dairy bail:

• the farmer can regulate the quantity ofeach cow’s supplement dependingupon her milk production or stage oflactation.

Disadvantages of this form of feeding:

• each cow receives a ration of the samecomposition, despite differences inlactation stage or production

• only feeds that can readily moved byaugers can be used, and this can restrictthe use of by-product feeds

• dusty feeds can cause respiratoryproblems in dairy workers and couldcause quality problems in milk.

Feed troughs. Feeding a supplement onthe ground is a wasteful exercise and candramatically increase the overall cost ofusing the supplement. At least 50% of thesupplement might not be eaten because ithas been trampled by the cows.

Troughs can be used to feed out alltypes of supplements, including foragesupplements. However, unless special


2.8

content, the protein quality (including RDPand amino acid content), the proportion ofcrude protein percentage which is urea, andthe quantity of added minerals, vitaminsand other additives. Get this informationfor every new shipment of pellets.

Pre-mixed supplements

Local feed merchants and feed companiescan supply supplements ready for use onthe farm. You can decide on the mix, or aprivate nutrition consultant or anutritionist employed by a feed companycan do it.

The advantages of using these mixesover pellets is that you have more controlover the ingredients, which can beadjusted to suit changes in other parts ofthe ration. The mix can be fed directlyinto the dairy bail or a feed trough, ormixed with a forage before feeding out. Afeed mixer and labour is required.

Home mix

Mixing the cow’s ration on-farm allowsyou to buy the ingredients you want andthen mix them to your cows’ requirementsto a recipe devised by you or a nutritionalconsultant. You can buy ingredients likegrains and by-products more cheaply inbulk, but you need plenty of storage. Ifyou don’t have enough storage and haveto buy bagged feed, the price of thesupplement will increase dramatically.

The capital equipment required forhome mixes can be expensive. Theminimum requirement is a good feedmixer. If cereal grains have to beprocessed, you will need a rollermill orhammermill. If you are using more thanone supplement, you might need a numberof augers. If the feed mix has multipleingredients and/or forage must be added,then you will need a feed wagon capableof weighing ingredients as they are added.Without the correct equipment, home

feeding equipment (such as a feed wagon)is used, feeding-out can be labourintensive, especially if the trough is aboveground level. Clean the troughs andremove all uneaten food before you addnew feed; doing this is labour intensivetoo.

There should be enough space at thefeed trough for all cows. If there is notenough space, heifers and the lessdominant cows in the herd will bedisadvantaged.

Feed pads. A feed pad can be set up usinga fence line or an electric fence to stop thecows walking on the feed, or it can be aconcrete-based feeding area with headbails in a feed shed.

As with trough feeding, the use of feedpads can be labour intensive if you do notuse equipment to feed out and to clean theuneaten feed from the pad.

Pelleting

Pelleted feed is available commercially.The main advantage of using pellets is

the convenience—there is no need forcapital equipment such as a feed mixer orfor a labour unit for processing the feed,there is little dust if the pellets are fed inthe dairy bails, and there is no risk ofcows selectively eating part of the rationand neglecting another.

The main disadvantage with usingpellets is the lack of control the farmer hasover the composition of the feed in thepellet and the quality of the feedingredients. One component inthe feed—such as the cereal grain source—can bechanged between shipments, and this canlead to digestive problems in the cow. Theingredients cannot be changed to ‘fine-tune’ the ration if there is a change in thequality of the forage component.

When you buy pellets, ask for thenutrient analysis of the pelleted ration.The analysis should show the energy


2.9

mixes can be very labour intensive as wellas inaccurate. Making a poorly mixedsupplement can be an expensive exercise.

The cost of supplying a good homemix may exceed any savings you make bybuying cheaper ingredients, especially insmall dairy herds. The economies of scaleoccurring in larger dairy herds (greaterspread of fixed costs over greater totalmilk production) make home mixes moreprofitable than other methods ofsupplementation.

How do I choose a cost-effective supplement?

Many supplements have similar nutrientvalues. Which supplement should I use?

One method of selecting supplementsis by their unit cost. This is the cost perunit of nutrient (which can be energy,crude protein or UDP).

The basic formula is:

Cost per tonne delivered of feed)

1000 × (nutrient content in diet) × DM %

in $/ MJ.

So if barley is $190 a tonne delivered,the DM content is 90% and the energycontent is 12 MJME/kg DM, then the costper unit of energy is:

190 or 1.7c/MJ.

1000 × 12 × 90/100

Supplements may provide more thanone nutrient, so you should work out thecost of the other nutrients using theequation above. For example, brewersgrain provides both energy and proteinand can be a source of UDP.

Remember, though, that cost is onlyone factor involved in selectingsupplements. You should consider all theingredients in the ration when you select asupplement.


2.10


3.1

Working out a ration


The nutrients in the dairy cow’s diet mustbe in the right proportion to keep herhealthy and support milk production,pregnancy and growth. Any imbalance inthe ration can result in poor milkproduction or other signs of ill health.Remember that we are also feeding thecow’s rumen as well as the cow.

To get the correct balance in the rationwe must calculate the cow’s requirementsfor maintenance, growth, milk production,pregnancy and overall activity, and thenmatch these to the nutrients provided inthe feedstuffs we intend to use to make upthe ration.

In many cases, you can devise a basicration using a pen, paper and calculator.There are also several computer packagesthat can help you formulate a cow’s rationin more detail than by hand.

The computer packages are tools forhelping with complex calculations; don’texpect the computer to substitute for theknowledge you do not have.

A computer is only accurate when theinformation you give it is accurate—itcan’t make concessions for mistakes infeed analysis or estimations of cow feedintake.

In this section, you will:

• learn what information you need tocollect before you start doing yourcalculations or using a computerpackage

• work out whether a sample ration isadequate.


• completion of Sections 1 and 2 of thismanual

• basic computing skills.

Guidelines for feedingdairy cattle at differentstages of lactation

Before you work out your ration you mustget clear in your mind what your cowsneed at this moment . The dry matterintakes and energy requirements of dairycattle vary according to their live weight,milk production, activity, body conditionand stage of pregnancy. Methods forestimating these values have been given insection 1 under ‘What nutrients does thecow need?’.

The guidelines in table 3.1 are basedon cattle receiving a total mixed ration.Some figures (such as the crude proteinfigures) are higher than those normallyquoted for pasture-fed cattle. The highermilk production of these cattle and theinclusion of nutrients such as fat in thesediets make these higher requirementsnecessary. These rations are formulated tomaximise the amount of microbial proteinproduced in the rumen by balancing thedietary carbohydrate and protein.

If you need to know the amount of anutrient in grams per kg DM, multiply thepercentage value by 10.

What else do I need toknow before I canbalance a cow’s diet?

Important abbreviations

We discussed the following abbreviationsin Section 1; refer back to this section ifyou don’t remember what thesemeasurement units mean.

DM Dry matter


3.2

Table 3.1: Nutrient needs of dairy cattle at various stages of lactation

CP Crude protein

RDP Rumen degradable protein

UDP Undegraded protein

NPN Non-protein nitrogen (such asurea)

ME Metabolisable energy,expressed as megajoules ofmetabolisable energy perkilogram dry matter (or MJ ofME/ kg DM)

kg kilogram

Milking Dry cow

Early Mid Late Dry Springer

Protein

CP (%) 17.5ñ19.5 15ñ17 14ñ15 12 14.5ñ15

UDP (as % ofCP)

35ñ40 33ñ37 30ñ36 30ñ35 33ñ38

Carbohydrate

ADF (min. %) 17ñ21 19ñ22 21ñ25 30ñ35 25ñ29

NDF (min. %) 28ñ31 28ñ33 34ñ40 42ñ50 37ñ43

Min. forage NDF(%)

18ñ23 19ñ23 21ñ25 35ñ38 31ñ34

NSC (%) 35ñ42 34ñ43 32ñ45 30ñ40 34ñ40

Min. forage indiet (%)

40ñ45 45ñ50 50ñ55 60 55

Energy

Average energyof ration (MJME)

11.4 11.2 10.6 8.9 9.9

Total fat (%) 5ñ7 5ñ6 3ñ5 3ñ4 3ñ5

Macro-minerals(% of ration)

Calcium 0.80ñ0.85 0.70ñ0.80 0.65ñ0.75 0.60ñ0.80 0.60ñ0.80

Calcium if diethas added fat

0.90ñ1.10 0.90ñ1.00 0.85ñ0.95 ñ ñ

Phosphorus 0.48ñ0.55 0.43ñ0.47 0.38ñ0.42 0.30ñ0.36 0.34ñ0.40

Magnesium 0.32ñ0.40 0.28ñ0.35 0.25ñ0.30 0.18ñ0.20 0.20ñ0.25

Potassium 1.20ñ1.40 1.00ñ1.20 0.90ñ1.00 0.70ñ0.80 0.70ñ0.80

Sodium 0.20ñ0.30 0.18ñ0.25 0.18ñ0.25 0.10 0ñ0.10

Chlorine 0.25ñ0.30 0.25ñ0.30 0.25ñ0.30 0.20 0.20

Salt 0.25ñ0.50 0.25ñ0.50 0.25ñ0.50 0.22ñ0.25 0ñ0.25

Sulphur 0.20ñ0.25 0.20ñ0.25 0.20ñ0.22 0.16ñ0.20 0.16ñ0.20

Nitrogen:sulphur ratio(N:S)

11ñ13:1 11ñ13:1 10ñ12:1 10ñ13:1 5ñ12:1


3.3

Table 3.1: Nutrient needs of dairy cattle at various stages of lactation continued

Information you must knowbefore you formulate a ration

If we want to formulate a ration for cows,whether by using a pen, paper andcalculator or a computer package, we needto know the following information:

Average cow live weight (kg)

This can be assessed for the herd or it canbe assessed for different lactation groupssuch as early lactation (up to 100 days),mid-lactation (100–200 days) and latelactation (over 200 days). If a ration isbeing formulated for heifers or dry cows,estimate their weights too.

Live weight change (kg/day)

Cow live weights change throughout thelactation cycle. We can monitor thesechanges by condition scoring. We canestimate how much weight a cow needs togain or how much she could lose byscoring changes in her condition.

Condition scoring is explained fully insection 4. Important information toremember is that one condition scorechange in:

• Holstein–Friesians equals 42 kg liveweight

• Holstein–Jersey crosses equals 34 kglive weight

• Jerseys equals 26 kg live weight.

For Brown–Swiss and Australian Redbreeds (Ayrshire, Illawarras) use theaverage Holstein–Friesian values. ForGuernseys, depending on their size, usethe Jersey values or the crossbred values.Example: a Holstein–Friesian cow needs to puton one condition score between the third and thesixth month of lactation (from condition score 3.5to condition score 4.5).She should remain at thiscondition for the next three months of lactation.How much weight should she gain each day?

The cow needs to put on one condition scoreover the next three months. If the weight is to begained slowly, the daily weight gain would be 42kg divided by 90 days—or 0.5 kg/day.

Milking Dry cow

Early Mid Late Dry Springer

Micro-minerals(mg/kg DM)

Cobalt 0.5 0.4 0.3 0.3 0.4

Copper 20 15 12 12 20

Iodine 0.8 0.8 0.8 0.5 0.5

Iron 100 100 100 100 100

Manganese 70 60 50 60 70

Selenium 0.1 0.1 0.1 0.1 0.1

Zinc 80 70 60 70 80

Vitamins

Vit A◊ 1000 IU/day

150ñ250 100ñ150 75ñ100 75ñ100 100ñ150

Vit D ◊ 1000 IU/day

40ñ60 30ñ50 25ñ35 25ñ30 25ñ35

Vit EIU/day

600ñ800 400ñ600 300ñ500 400ñ600 600ñ1000


3.4

Milk yield (litres)

You need to estimate the potential milkyield for each lactation group as a whole.Some cows may produce more, and someless, depending upon their breeding,health (mastitis history, milk feverepisodes, lameness) and physiology (firstcalf heifer, pregnant cow). However, theaverage milk production for a groupshould be good enough for the purposes ofyour calculations.

Milk composition (% butterfat, %protein)

The energy needed to produce a litre ofmilk differs depending on the compositionof milk (see table 1.6). The cow uses moreenergy to produce a litre of milk with highbutterfat and protein than a litre of milkwith lesser composition.

Remember that there is a geneticinfluence over how much butterfat andprotein a cow can produce. Even the bestdiet will not achieve good milkcomposition in a cow if she does not havethe right genetics.

Estimated feed intake of the cow (kg/day)

Calculate the estimated daily intake of acow using the following equation:(2.2 x live weight + 20 x daily milk production) /100.

DM values

Every feed analysis will give a dry matterpercentage. Appendix 1 describes howyou can determine the dry matter on yourown pasture using a microwave orordinary oven.

We need to know the dry mattercontent of the feed because this valuedetermines how much feed the cow caneat. We should be able to convert the drymatter value to an as fed value so that weknow the total volume of feed that has tobe fed out or added to a mix.

ME and CP value of feeds

The ME and CP values of feeds are twoimportant measures for formulating aration if you are doing the calculationsyourself. You should also be aware of thefibre content (NDF and ADF), the types ofproteins present in the feeds (RDP, UDP,NPN), the digestibility of the feed and themineral and vitamin content. When youinclude these latter factors into theformulation, the calculations can becomecomplex. Fortunately, there are a numberof computer packages for rationformulation that not only do thecalculations but also have databasescontaining information on the analysis ofmost of the common feeds we use in dairycow rations.Example: A cow in mid-lactation with anestimated feed intake of 15 kg is being offered acereal grain – hay mix in a ration of 1 part grain to2 parts hay. The dry matter content of the grain is90% and the dry matter content of the hay is 75%.If we have 20 cows with these requirements, howmuch feed do we need each day?

The ration for a single cow will be 5 kg drymatter grain and 10 kg dry matter hay. We need toconvert the dry matter values to as fed values.This means that we need to include the moisturecontent of the feed. The as fed amount iscalculated by multiplying the dry matter amountin kg by the inverse of the dry matter percentage.Grain has a dry matter content of 90% or (90/100)so the inverse is (100/90).

So the total as fed amount is 5.6 kg grain (5 ∞100/90) and 13.3 kg hay (10 ∞ 100/75) for eachcow.

For 20 cows we will need to supply 112 kg ofgrain and 266 kg hay.

Handy hints

• One small bale of hay weighs 25–33kg.

• One large bale of hay weighs 440–600kg.


3.5

Working out whether a ration is adequate: step bystep example

Now that you have collected as much information about your cows and the feeds you intend to use,you should be ready to calculate whether the ration you are using is supplying all the needs of yourherd.

The following example calculates the requirements and ration for a 550 kg cow in late

lactation.This is the same cow we calculated the energy requirements for in section 1 of this manual(see page 1.18 of section 1).

After the example you may be asking the question, ‘Why aren’t my cows producing moremilk?’ There are many reasons why cows do not reach a certain production level. The genetics ofthe herd is one main constraint that cannot be solved in the short term, but there are other causesthat can be resolved—and the adequacy of the ration is one.

Now to fill in the charts. First work out the nutrient needs of your cow. You will need to refer tothe tables mentioned in the charts to get some of the figures.

Step 1: Work out your cow’s daily needs

Energy needed

Use this chart to calculate how much energy one cow needs:

Protein needed

Cowís live weight 550 kg

Months pregnant 6

Distance walked 4 km (flat terrain)

Weight gain needed 0.5 kg/day

Daily milk production 15

Milkcomposition

Fat % 3.8

Protein % 3.2

Predicted dry matter intake 15 kg

Energy needed for maintenance (table 1.4)

59 MJ

Energy needed for pregnancy (table 1.5) 8 MJ

Energy needed for activity 4 MJ

Energy needed for weight gain 17 MJ

Energy needed for milk production (table1.6)

78 MJ

Total energy needed (MJ of ME eachday)

166 MJ


3.6

Use this chart to calculate how much protein the cow needs:

Fibre needed

The minimum fibre content in the diet should be 19–21% ADF. If NDF values were available forfeed, then the NDF% should be from 25–30%.

Calcium and phosphorus needed

The minimum amount of calcium and phosphorus required is 0.65% and 0.38% of ration drymatter respectively. (see Table 3.1). The ratio of calcium to phosphorus in the diet should bebetween 1.2:1 and 1.5:1.

Table 3.2: Feed composition data

Step 2: Work out what the ration supplies

The ration to be fed in this example is a pasture/barley/lupins/hay mix. The estimated intake foreach cow is 25 kg of pasture, 4 kg of barley, 2 kg of lupins and 5 kg of hay.You can get information on the feed composition of the diet from a number of sources:

• Feed composition tables in books, farming magazines or hand-outs

• Results from the analysis of the feed by a feed testing laboratory

• Analysis information from the label of a feed product or information from the companywhich supplies the feed.

The dry matter percentage of pastures can be calculated using the microwave methodexplained in Appendix 1.

Table 3.2 contains information on feed composition that is used in this exercise.

Cowís live weight 550 kg

Days in milk or stage of lactation (early, mid,late)

late

Daily milk production 15 litres

Milkcomposition

Fat % 3.8

Protein % 3.2

Crude protein needed (g) (tables 1.7 and1.8)

460 + 1230 = 1690 g(12ñ14% of total diet)

minimum RDP needed (g) (table 1.9) 1168

minimum UDP needed (g) (table 1.9) 209

Composition of feeds on a dry matter basis

DM%

MJofME

CP(g)

RDP(g)

UDP(g)

Fibre(g)

Calcium(g)

Phosphorus(g)

Pasture 20 11 271 190 81 130 7.3 3.2

Barley 90 13.7 120 96 24 53 0.8 3.7

Lupins 90 13.2 300 180 120 140 2.2 3.9

Hay 90 8.4 86 60 26 330 6.2 3.4


3.7

Dry matter intake

kg dry matter eaten = kg eaten x dry matter percentage/100

Use this chart to calculate how much dry matter the cow is getting:

Energy intake

MJ of ME supplied to each cow = kg dry matter eaten x MJ of ME supplied per kg of dry matter.

Use this chart to calculate how much energy the cow is getting:

Dry matterpercentage

kg eaten per cow kg of drymattereaten percow

Pasture 20 25 5

Cerealgrain or pellet (barley)

90 4 3.6

Hay 90 5 4.5

Silage

Supplement 1(lupins) 90 2 1.8

Supplement 2

Total dry matter intake per cow per day 14.9 kg

MJ of MEsupplied per kgof dry matter

kg of dry matter eatenper cow (calculated inthe previous chart)

MJ of ME suppliedto each cow

Pasture 11 5 55

Cerealgrain or pellet(barley)

13.7 3.6 49.3

Hay 8.4 4.5 37.8

Silage

Supplement 1(lupins)

13.2 1.8 23.8

Supplement 2

Total energy intake per cow 165.9 MJ of ME


3.8

Protein intake

Use this chart to calculate how much crude protein the cow is getting:

Protein intake as RDP

Use this chart to work out the cow’s RDP intake:

% crudeprotein

g of crudeprotein perkg of drymatter

kg of dry mattereaten per cow(alreadycalculated)

g of crude proteinsupplied to eachcow

Pasture 27.1% 271 5 1355


12.0% 120 3.6 432

Hay 8.6% 86 4.5 387

Silage


30.0% 300 1.8 540

Supplement 2

Total crude protein intake per cow 2714 g

% RDP infeed

g of RDPper kg of drymatter


g of RDP suppliedto each cow

Pasture 70 190 5 950


80 96 3.6 346

Hay 70 60 4.5 270

Silage


60 180 1.8 324

Supplement 2

Total RDP intake per cow 1890 g


3.9

Protein intake as UDP

Use this chart to work out the cow’s UDP intake:

Fibre intake

Use this chart to calculate how much ADF the cow is getting:

% UDP g of UDPper kg of drymatter

kg of drymatter eatenper cow(alreadycalculated)

g of UDP supplied toeach cow

Pasture 30 81 5 405


20 24 3.6 86

Hay 30 26 4.5 117

Silage


40 120 1.8 216

Supplement 2

Total UDP intake per cow 824 g

Fibre(% ADF)

g of fibreper kg ofdry matter


g of fibre suppliedto each cow

Pasture 13.0 130 5 650

Cerealgrain or pellet

5.3 53 3.6 191

Hay 33.0 330 4.5 1485

Silage

Supplement 1 14.0 140 1.8 252

Supplement 2

Total ADF intake per cow 2578 g

Supplement 2

Total ADF intake per cow


3.10

Calcium intake

Use this chart to calculate how much calcium the cow is getting:

Phosphorus intake

Use this chart to calculate how much phosphorus the cow is getting:

Calcium (%) g of calciumper kg of drymatter


g of calciumsupplied to eachcow

Pasture 0.073 7.3 5 36.5


0.008 0.8 3.6 2.9

Hay 0.062 6.2 4.5 27.9

Silage

Supplement 1 0.022 2.2 1.8 4

Supplement 2

Total calcium intake per cow 71.3 g

Phosphorus%

g ofphosphorusper kg of drymatter

kg of drymatter eatenper cow(alreadycalculated)

g of phosphorussupplied to eachcow

Pasture 0.032 3.2 5 16


0.037 3.7 3.6 13.3

Hay 0.034 3.4 4.5 15.3

Silage

Supplement 1 0.039 3.9 1.8 7

Supplement 2

Total phosphorus intake per cow 51.6 g


3.11

Step 3: Put it all together

Summary of cow’s daily requirements

Use this chart to summarise the cow’s daily needs:

Summary of cow’s daily ration

Use this chart to summarise the cow’s daily intake:

Now you have all the figures written down in the charts, study them carefully. Does the rationhave sufficient energy, protein and fibre to supply the cow’s requirement for maintenance,pregnancy, activity, milk production and weight gain?

• For this cow, she is eating to capacity and there is adequate energy supplied in the ration forher needs.

• These is too much crude protein.

• Fibre intake is borderline.

• Even though the calcium to phosphorus ratio is in the correct range, the ration is deficient inboth calcium and phosphorus.

Adding calcium and phosphorus to the diet would be the major change. Adding dicalciumphosphate (310 g calcium per kg DM; 130 g phosphorus per kg DM) at the rate of 0.08 kg per

Predicted dry matter intake per cow 15 kg

Total energy needed for the cow (MJ ofME/day)

166 kg

Crude protein needed 1690 g

minimum RDP needed 1169 g

minimum UDP needed 209 g

minimum calcium needed 97.5 g

minimum phosphorus needed 57 g

Total dry matter intake per cow 14.9 kg

Total energy intake 165.9 MJ of ME

Crude protein intake 2714 g

Crude protein percentage 18.2%

RDP intake 1890 g

UDP intake 824 g

Total fibre intake 2578 g

Total fibre percentage 17.3%

Total calcium intake 71.3 g

Total phosphorus intake 51.6 g

Calcium to phosphorus ratio 1.38: 1


3.12

cow per day would increase the calcium content of the ration by 24.8 g and the phosphoruscontent by 10.4 g.

Removing the lupins from the diet and increasing the barley and hay content may be asolution if the excessive protein and marginal fibre are considered detrimental to the cow’sproduction. Hay has less RDP and more fibre; although it has less energy it is sufficient.

Note that adding hay and grain would slightly change the calcium and phosphorus intake.The ration should be formulated to suit the majority of cows in the herd. The cows’

requirements will change during lactation and the dry period (see Table 3.1). In some cases asingle ration will not be suitable. If the dairy herd is large, it could be separated into ‘strings’(groups of cows at the same stage of lactation) that can be fed rations of different energy, proteinand UDP levels. Some farmers may opt to feed different amount of concentrate in the milkingbails to achieve the same result. The downside with the latter method of feeding is that somecows may be receiving too large a ‘slug’ of high energy – low fibre feed, such as cereal grain,which would upset the activity of the microbes in the rumen. A balanced bail feed such asformulated pellets may decrease the chance of these upsets occurring.

Can I use a computer forration balancing?

Teaching the use of a computer packagefor developing a ration for a herd isbeyond the scope of this manual. Thereare a number of computer packagesavailable and training courses for use ofthese packages are available. You mayalready have a nutritional adviser whouses a computer package.

With any computer program, the valueof the output from the program dependson the quality of the information enteredand how the information which isproduced is interpreted. Never assume thatthe computer is always right. There is anold computer term, ‘GIGO’, which means‘garbage in—garbage out’.

Consider the computer and anysoftware package as a ‘dumb slave’. Thecomputer will do all the complexcalculations needed to determine the valueof a ration for your herd. It will calculatethe amount of milk that could beproduced. It will show the adequacy of theration for all nutrients (includingminerals) and for maintaining orincreasing body condition. One furthercalculation that can be done is the totalcost of feeding your cows for each litre ofmilk produced.

One feed ration computer program fordairy farmers is CAMDAIRY. Before youuse this program, you will need thefollowing information about your farm,your herd and the feeds you intend using.

Milk production details

• peak milk production (the amount ofmilk the average cow should produce6–10 weeks after calving)

• average milk fat percentage

• average milk protein percentage

• total weekly milk production formarket milk (quota) and price receivedper litre

• total weekly milk production formanufacturing and price received perlitre.

Herd details

• breed of cow

• number of cows in milk

• average adult live weight

• average condition score of the cows(degree of fatness)

• percentage of heifers in the herd

• average heifer live weight

• average heifer condition score

• average number of weeks since calving(average ‘days in milk’) for the herd


3.13

• average number of weeks pregnant

• activity level of the herd. The amountof walking the cows have to do eachday depends on the terrain of the farmand the feeding system used. The cowsmay be kept in a feedlot, on abundantpasture, sparse pasture or very hillyterrain. The amount of energy abovemaintenance needed in the diet tocompensate for this activity iscalculated by the farmer.

The dairy herd may be separated intodifferent groups for milking or forfeeding. The information above can beredone for each group of cows in theherd—for example, early lactation cowsare fed a separate ration from mid- andlate lactation cows.

Feed information

List all feeds in the ration, includingthe type and stage of maturity of pasture.Estimate the amount of each feed fed to anindividual cow on an ‘as fed’ or ‘drymatter’ basis. Estimate the cost of eachfeed per tonne (including the cost ofproducing pasture).

The computer program has a databasewhere the information on most feeds arestored. If you are using a feed or pasturethat is not in the database, you can enterinformation on its nutrient content into theprogram if you have the feed analysisresults for that feed. If you are missingdifferent information on a feed (such as itsNDF or mineral content), then the overallanalysis of the ration generated by thecomputer will be deficient in thesenutrients.


3.14


4.1

Fine-tuning your feeding

How do you measure the success of theration you are feeding? The most obviousmeasure is milk production—but what ifthe cow is a growing heifer or dry? Thenyou must use condition scoring. Bodycondition scoring is an important tool fordetermining whether a ration is adequatefor body maintenance at different stagesof growth and lactation.

If the ration is imbalanced, the cow canshow signs of ill-health. These conditionswill often require veterinary treatment, butthey can be prevented by using the properration.

This section will help you tounderstand these and other issues youneed to know about if you are to fine-tuneyour rationing.

In this section, you will:

• learn about and use body conditionscoring

• learn to recognise the differentmetabolic diseases

• learn how changes in diet can affectmilk composition

• gain a better knowledge of the role ofmacro minerals and micro minerals ina cow’s ration

• learn about the use of transition rationsfor springer cows.



• sections 1, 2 and 3 of this manual

• general knowledge of dairy cows.

Body condition scoringWhy measure body condition?

It is normal for cows to use their bodyreserves and lose weight in early lactation.

If a cow loses too much body weight atthis time she will be much more prone tometabolic diseases such as ketosis oracetonaemia.

It is important to manage live weightloss by feeding correctly, so that there isno adverse effect on milk production orthe ability to get in calf.

Cows that are thin at calving willpreferentially gain weight after calving,when they should be putting all theirenergy into milk production.

Cows that lose more weight duringearly lactation for milk production aremore prone to metabolic diseases such asketosis and poorer fertility.

One body condition score equals:

• 42 kg live weight in a Holstein–Friesian

• 34 kg live weight in a Friesian–Jerseycross

• 26 kg live weight in a Jersey

At calving, one body condition scoremeans an extra:

• 130 litres milk

• 10 kg butterfat

• 15% butterfat

during the first 20 weeks of lactation.

How does body conditionscoring work?

Body condition scoring (BCS) tells us theamount of stored energy reserves in acow’s body. These reserves affects health,production and reproduction.

There is no one ideal BCS for a cow;instead, there is a range of desirablescores that can vary during lactation andthe dry period. It is the change in BCS forindividual cows over time that isimportant. Body condition score charts


4.2

available from some animal healthcompanies will give you a good guide towhat to look for.

By regularly evaluating the bodycondition of your cows and heifers youcan fine-tune their feeding management.BCS is an essential tool for theprogressive farmer. It can be masteredwitha little training and by using goodobservation skills.

In Australia we use BCS from 1–8. Inthe USA, BCS ranges from 1–5. Toconvert from the American system to theAustralian system, simply multiply theBCS by 1.6 or multiply by 8 and divide by5.

When is the best time to scorethe cows?

• at calving

• after calving

• at the time of mating (either naturalmating or artificial insemination)

• when you are checking cows forpregnancy or at mid-lactation

• at drying-off

• during milking time, when the cowsare in the yard.

BCS 1—8 system hints

The BCS technique is subjective, so thesame person needs to score the cows on aregular basis for the scores to berepeatable. However, on occasions youshould get someone who does not see thecows every day to condition score thecows, just to keep you on track. Workingwith cows every day can make you lessaware of changes in their condition.

Regular monitoring of first and lastbatches of cows through the dairy is allyou need to do. However, you might wantto condition score cows at different stagesof lactation.

What should the BCS be atdifferent times?

Early lactation

In early lactation the cow’s appetite isonly 75% of her potential intake of drymatter. Her energy requirements for milkproduction exceed her appetite. Her bodyreserves are used to make up the deficit,so she will lose weight during the first 100days.

Cows should calve at BCS between 5and 6. These cows have a greater chanceof reaching peak milk yields, and theirpeak yields and lactations persist longerproviding the ration is both adequateand balanced.

They should lose a maximum of 1.5condition scores during the first monthafter calving when they are in negativeenergy balance. If cows lose morecondition it could be difficult to get theminto calf.

Cows calving at lower BCS will havepoor body energy reserves for peaklactation and reproduction. These cowswill direct many of the nutrients in theirdiets into improving body condition. Milkproduction will suffer as a result. Theymay not start their heat cycles for morethan 40 days after calving.

Cows calving at higher BCS may havedifficulty at calving because fat in thebirth canal can prevent normal birth. Fatcows are prone to a number of metabolicdiseases, such as ketosis, where the by-product of fat metabolism builds up in theblood stream, affecting normal liverfunction. The liver is important inconverting chemicals absorbed from therumen into energy (glucose) and body fat(triglycerides). It is also important inremoving toxins from the blood. Inserious cases, the by-products can give an‘acetone’ smell to the breath.


4.3

Mid-lactation

In mid-lactation the cow is able to eatmore dry matter, and this enables her tomeet the demand for milk production andearly pregnancy without using her bodyreserves. This means no major weight lossor gain during this second 100 days. Cowsmay reach BCS 4 at this time.

Late lactation

In late lactation a cow’s appetite exceedsher requirement for energy, so she puts thenutrients in her feed towards gaining bodycondition over the 100 days in order toprepare herself for the next lactation. Thecow needs to be at BCS 5 by drying-offtime.

Dry period

A cow puts on weight more efficientlyduring late lactation than when she is dry.If the cow dries off at BCS 5 she needs tobe maintained only at that score duringthe dry period. This helps stop her gettingover-fat and having calving problems, ordeveloping metabolic disorders in the nextlactation.

About 1500 MJ of ME are required foreach BCS unit gained by a lactating cow.About 2000 MJ of ME are required foreach BCS unit gained by a dry cow. Thismeans that more feed will be needed foreach BCS unit if the cow is to put oncondition when she is dry.

Understanding themetabolic and nutritionaldiseases of dairy cows

There are four main metabolic diseasesthat you need to know about if your cowsare to stay healthy and make good weightgains:

• hypocalcaemia (milk fever)

• hypomagnesaemia (grass tetany)

• ketosis (acetonaemia)

• acidosis (grain poisoning).

Milk fever

Cause

This is a common disease in highproducing dairy cows. It occurs whenthere is a rapid fall in blood calcium level,usually at about the time of calving. Thefall in calcium is caused by a reducedabsorption of calcium from the gut and aninability of the cow to mobilise calciumfrom her skeleton, the main reserve ofcalcium in the body. This fall occurs at atime when there is a huge demand forcalcium with the onset of milk production.Most cases of milk fever occur within 3days of calving.

A daily milk yield of 30 litres containsabout 36 g of calcium. This is about fourtimes the level of calcium in the blood.The cow must mobilise the calcium fromher skeleton very rapidly to maintain theblood calcium level.

Predisposing factors

Milk fever is more common in third andfourth lactation cows. Older cows have agreater demand for calcium because oftheir higher milk production. The cows atrisk are usually high producers in goodbody condition. Milk fever is more likelyto occur in cows milked out completelywithin the first 48 hours after calving thanin those cows left with their calves.(However, other problems, such asmastitis, can arise if high producing cowsare not milked out during this time.)

Milk fever can increase when theenvironmental conditions are cold andwet. Under these conditions cows maygraze less, so that their calcium intakedecreases.

Jersey breed cows are more susceptibleto milk fever than other dairy breeds.


4.4

Signs

Milk fever is commonly seen within 3–4days after calving when milk productionis increasing. Cows with milk fever atcalving can often have another episode 3–4 days later.

A cow with milk fever can be excited,off her feed, show trembling in themuscles and grind her teeth. Most cowswill lie down and appear drowsy, withtheir heads to the side. The muzzle is dry.The cow often does not pass any faeces.

The cow will be unable to stand, andshe is if untreated she will becomecomatose and have loose limbs. Once sheis lying flat on the ground she will quicklybloat and often die from inhalingregurgitated rumen contents.

Diagnosis

Milk fever must be differentiated fromcalving paralysis (from a difficultdelivery) as well as acute infections of thegut, udder (black mastitis) and uterus—any of these diseases may occur at thesame time.

A blood test for calcium may help thevet to reach a diagnosis. The blood sampleshould betaken before any treatment isgiven.

Treatment

It is essential to increase the cow’s bloodcalcium level by giving prompt treatmentwith a solution containing calcium If thecow is still standing, the calcium solutioncan be given subcutaneously (under theskin). Cows that are lying down can begiven the calcium solutionsubcutaneously, although in some it willneed to be given into a vein(intravenously). This treatment should begiven by a veterinarian because thecalcium solution can be fatal if it is giventoo fast into the vein.

The response to the injection is usually

fast, and cows may be standing andappearing ‘normal’ within 10 minutes oftreatment. If the cow does not respondquickly, she should be checked by aveterinarian. She may need anothertreatment, or she may not have milk fever,or she may have milk fever complicatedby another disease.

Prevention

Currently there is a debate about the bestway to prevent milk fever. Traditionallyrations that are low in calcium are fedbefore calving. Theoretically thistreatment will stimulate the cow tomobilise calcium from her body reserves.Diets high in calcium (like lush pasturesor hays rich in clover and lucerne) areavoided.

Feeding rations low in ‘positive’ ionssuch as potassium and sodium helps tocreate a slightly ‘negative’ environment inthe cow’s body; this stimulates the cow tomobilise calcium. Normal feed additivessuch as salt (sodium chloride), sodiumbicarbonate and lime (calcium carbonate)supply ‘positive’ ions to the diet andshould not be fed to springers. Neithershould causmag or magnesium oxide.Special springer rations can beformulated; they contain ‘anionic salts’ tohelp create the ‘negative’ environment.One anionic salt that is commonly used ismagnesium sulphate. The anionic balanceof the entire ration (including thecontribution of the positive and negativeions in any pasture or forage that is fed)has to be calculated. The calcium contentof these diets can be variable—either lowor high. Because of the specialistknowledge needed for the use of anionicsalts, all rations containing these saltsshould be formulated by a nutritionalconsultant.

An injection of 250 mg Vitamin D 2–8days before calving can help. The date ofcalving should be accurate.


4.5

Calcium gels can be given orally 24hours before and after calving to cows thatmay be at risk of milk fever. You can use aurine test to detect these cows. The testmeasures the urine pH.

Adding 70% cereal hay to the springerration can reduce the occurrence of milkfever by reducing calcium intake andencouraging rumination.

Summary

• reduce sodium and potassium levels inrations

• remove bicarb, lime and salt fromrations

• avoid high legume pastures and hays

• provide shelter from bad weather

• avoid long periods of limited feedaccess

• use vitamin D injections for high riskcows

Grass tetany

Cause

Grass tetany occurs when there is a rapidfall in blood magnesium. It is commonlyseen in high-producing dairy cows,particularly in the spring.

Cows cannot store much magnesium intheir bodies and require a daily intake ofmagnesium in the diet. a cow producing30 litres will be losing about 30 g ofmagnesium in her milk each day.

Pastures can have very variableamounts of available magnesium.


Grass tetany is more likely to be seen inspring when lush pastures are low inmagnesium. These pasture usually have ahigh ammonia content, which depressesthe amount of magnesium available. Highlevels of calcium in the soil can reduce theuptake of magnesium by the pasture. Theuse of potash (potassium) fertilisers can

reduce the levels of available magnesiumin the pasture.

Stress is a major factor in thedevelopment of grass tetany in cows. It ismore likely to be seen when there is wetand cold weather. Newly calved, over-fatcows are more at risk of developingtetany.

Signs

The main clinical signs of grass tetany arecaused by excitation of the nervoussystem. The cow can show twitching ofthe muscles (especially in the face), thegait can be staggery and the demeanourexcitable. A normally quiet cow may tryto charge. The cow may collapse,convulse then die.

Diagnosis

A blood test will show if the bodymagnesium is low. Low blood calciummay also be present and may precipitatetetany.

Not all cows with low bloodmagnesium will show tetany. Any stresssuch as yarding, movement or feeddeprivation can bring on tetany in thesecows.

Prevention

Magnesium oxide (causmag) can besupplemented in the feed at about 60 g percow per day. Alternatively, magnesiumbullets can be placed in the rumen, or thepasture can be dusted with magnesiumoxide at the rate of 125 kg a hectare.

Since an excess of ammonia in thepasture can be a problem, energy

Treatment

Cows with obvious signs of grass tetanyshould be treated with an intravenousinjection of magnesium salts. Theseinfusions are usually combined withcalcium, and they are given very slowly toavoid cardiac arrest.


4.6

supplements can be fed to balance theexcess. There should be limited use ofpotash-based fertilisers.

At the times of the year when grasstetany could occur, try to avoid stresseslike yarding.

Ketosis

Cause

In early lactation, cows can be in anegative energy balance where theycannot eat enough to supply their needsfor maintenance and milk production. Asa result they will be mobilising their bodyfat.

Ketosis can occur if the mobilisation ofbody fat is excessive, especially if thecows are being underfed. Stress resultingfrom cold, wet conditions can precipitateketosis in early lactation cows because oftheir increased energy requirements formaintaining body heat.

Cows that calve in too good acondition (BCS 6 or higher) can developketosis.


Cows that carry too much fat at calvingand cows that are underfed after calvingcan develop ketosis. The liver cellsaccumulate fat, which impairs the abilityof the liver to make the glucose that thecow needs for energy.

Over-conditioned cows that loseweight during the dry period can alsoaccumulate fat in their livers and be proneto ketosis at the next calving.

Other factors include feeding highlevels of concentrates twice daily andfeeding poorly fermented or rancid silagethat contains high levels of butyric acid.

When cows have reduced appetitesbecause of other illnesses or because theyhave restricted access to feed, a disordersimilar to ketosis can develop. The maincause of this disorder is weight loss

following reduction in intake.

Signs

Affected cows lose weight and look dulland gaunt. Their breath may have a sweetsmell similar to that of acetone. There is adrop in milk production, but the milk fatpercentage of the milk increases. The cowmay be constipated and show changes inbehaviour. She may selectively eatroughages.

Diagnosis

Blood samples can indicate low bloodglucose and raised betahydroxybutyrate(blood ketone) levels. Ketones orbetahydroxybutyrate can be detected inthe urine. Acetone is found in the bloodwhen any condition causes a loss ofappetite.

Treatment

Glucose can be given intravenously (500–800 mL of a 40% solution), followed by600 mL of glycerine twice daily for thenext 2–3 days. An injection of cortisonemay be used if the cows are affected bystress.

Other treatments include drenchingwith Ketol® or propylene glycol for 7–10days before calving, and feeding goodquality hay.

Prevention

The appetite of the cow should bemaintained by supplying adequate feed tomeet her dry matter intake and byproviding high quality roughage. The cowshould not be allowed to calve in poorbody condition or in too-fat bodycondition. Assess her body condition scoreduring late lactation to make sure shedries off in BCS of about 5. The dry cowshould be fed to maintain this bodycondition score until calving. Beforecalving, the cow should receive a springerration, which helps to increase her dry


4.7

matter intake. Rumensin® added to thefeed at a rate of 200–250 mg per cow perday can help prevent ketosis.

Changing milkcomposition by changingthe ration

Introduction

It is important to know the nutritionalfactors affecting milk composition. Theseinclude the type of feed and the level ofintake. These interact, however, with anumber of non-nutritional factors, such asbreed, disease, stage of lactation andclimate.

The effects of feeding on compositionare complex; while theories provide useful

Acidosis

Cause

There are three important causes ofacidosis:

• lack of adequate long fibre in the diet

• feeding too much rapidly fermentablecarbohydrate (such as starchy grains orpellets)

• feeding too many kilograms ofconcentrates in one feed, or rapidlyintroducing grain into a cow’s ration.

Signs

The first sign of acidosis in a herd is alowered milk fat percentage. The affectedcow can show a slight drop in milkproduction and will go off her feed. Shescours, with sweet, sludgy faeces. She canstop ruminating and might showabdominal pain by having a tuckedappearance. Cows with severe cases ofacidosis can develop lameness in all fourfeet, and some may die following severedamage to the wall of the rumen.

Treatment

Drench affected cows with sodiumbicarbonate. Feed sodium bicarbonate atthe rate of 200 g per cow per day.

Reduce the level of concentrates in thediet and increase the percentage of goodhay in the ration.

In some cases, a veterinarian has toopen up the rumen and remove the grain.The contents are replaced with hay, waterand rumen liquor from another cow to help‘kick-start’ healthy rumination.

Prevention

Ensure the diet contains adequate fibre (see‘What nutrients does the cow need?’ insection 1).

Feed buffers (such as sodiumbicarbonate) in the ration (see ‘What feedssupply these nutrients?’ in section 1). Ifyou are feeding high-starch cereal grains(such as wheat or triticale) you must usebuffers.

If you must feed a high percentage ofconcentrate, it is better to give theconcentrate in many small feeds ratherthan two ‘slugs’. The rumen bacteria canhandle the smaller amounts of grain better.


Predisposing factors are:

• feeding high levels of grains in thedairy bail (‘slug’ feeding)

• sudden changes in diet and not usingfeed buffers (such as sodiumbicarbonate)

• grain feeding, in combination withfeeding young lush fibre with a lowNDF % and not feeding hay or silagewhen increased dietary fibre is needed.

Feeding low pH silages can causedigestive upsets similar to acidosis.


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predictions they cannot produce absoluterecipes for improving milk composition.

If most of the herd is calved at a certaintime of year, then 2–3 months afterwards,milk fat and protein levels will be at theirlowest. If a spring flush occurs at the sametime, then milk fat will drop furtherbecause of the low fibre levels in thepasture.

After a further 2–3 months milk fatand protein slowly increase until drying-off.

Factors affecting milk fatcontent

Milk fat is most sensitive to dietarychanges. Milk fat composition may fallabruptly when dairy cows are fed highlevels of digestible carbohydrates and lowlevels of fibre, when unsaturated fats areincluded in the diet, or simply when cowsare underfed.

Areas to consider include:

Roughage to concentrate ratio

The primary factor affecting miik fatpercentage is the level of fibre in the diet.Milk fat composition drops onceconcentrates reach 50 per cent of the dietor crude fibre levels drop below 17 percent.

Carbohydrate type

In high grain – low forage diets the typeof grains and the degree of processinghave an effect on milk composition.Finely ground wheat can cause thegreatest falls in milk fat percentage.

Level of feeding

At adequate levels of feeding, changes inmilk composition depend on dietcomposition. With underfeeding, the fatpercentage rises and milk production isreduced. Continued underfeeding,however, reduces fat content. The degree

of reduction depends on the duration ofunderfeeding and is related to the bodycondition of the cow.

Added fat

Production responses to the addition of fathave been variable and influenced by thetype of fat. Unsaturated fats (for example,vegetable oils) may depress fat levels,while saturated fats can improve the fattest. Protected fats have increased milkproduction, but with variable results onmilk fat content.

Whole oilseeds can elevate fat tests dueto the slow release of fat in the rumen.Recent dry fat products have improved thefat test and milk yield.

Dietary protein

In general, protein has a small effect onthe fat content of milk, although in lowroughage/high grain diets, fat levels areoften increased with additional protein inthe diet.

Factors affecting milk proteinlevels

Ways to increase protein levels in milk dueto nutrition are less apparent than changesin fat levels, since the genetic scope toincrease protein is less.

Level of feeding

Underfeeding reduces protein levels, anddiets with insufficient energy can depressmilk protein levels by 0.3 per cent.Conversely, increasing the feeding levels ofunderfed cows raises milk protein levels(see Figure 4.1).

Energy intake

Increased energy intake can increase milkprotein levels, but responses vary becauseof a number of factors:

• the level and duration of underfeedinghas a variable effect as mentioned above


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Various feeding studies have shown that:

• increased availability of high qualitytropical or temperate pastures increasesprotein levels

• clover is a superior feed for productionand composition

• milk protein responses to the inclusionof grain depend on the type and levelsof pasture intake

• at high levels of grain feeding (forexample, 7 kg/day), particularly withlow quality roughages, includingprotein (i.e. 18–20% CP in theconcentrate) increases the milk proteincontent

• attempts to manipulate protein in milkby feeding low levels of grain andprotected protein have been highlyvariable. The most consistent resultshave been achieved with formaldehydecasein. Formaldehyde-treated and heat-treated vegetable meals have generallyresulted in increased milk yield butincreases in protein content have beenvery inconsistent.

Note: The other main component of solidsnot fat (s.n.f.) is lactose. Studies show thatgrain fed to underfed cows increaseslactose levels and subsequently raisess.n.f. At adequate levels of feeding,lactose is normally unaffected by changesin feeding.

Summary

In summary, the nutritional factors affectingmilk composition are:

• Cows have a genetic milk compositionpotential and proper feeding allowsthem to reach their potential milk yield.

• With variations in composition the milkprotein test generally follows milk fatlevels unless feeding is abnormal.

• Genetic selection is the long-term

Figure 1: Effect of intake of pasture onmilk composition (Ellinbank trials)

• energy is first used to meet maintenancerequirements, then production functions(for example, liveweight, milk yield andmilk composition). Responses tosupplements by underfed cows cansubsequently be slow (3-4 weeks)

• cows in early lactation responddifferently to cows in mid to latelactation due to the differingphysiological drive to produce milk

• immediate responses to grain can below with well fed cows; however, inthe long term high levels of milk ofhigh composition are produced

• cows that are continuously well fedmay be close to their genetic limit formilk composition (particularly protein)

• high levels of feeding of wellconditioned cows support high levelsof milk production and composition

• the benefits of full feeding are carriedfrom one lactation to the next

• only minor differences have beenreported in response to the type ofgrain and degree of processing inpasture-based diets. That is, 30 per centconcentrates)

• there is often a substitution effect whenlarge proportions of grain are fed, andthis compounds the problems ofpredicting responses.

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4.6

4.7

4.8

4.9

7.5 8.5 9.5 10.5 11.5 12.5

INTAKE (KG DM / DAY)

FA

T %

2.8

2.9

3

3.1

3.2

PR

OT

EIN

%

FATPROTEIN


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method of improving the composition ofmilk, but feeding is the main factor inthe short term.

• Feed the right amounts of fermentablecarbohydrates to increase milk proteincomposition.

• High ration digestibility increases milkcomposition.

• Poor quality forage limits protein testand yield.

• Underfeeding reduces protein test andyield.

• Oils and fats depress protein test andyield.

• Various additives (e.g. buffers) givevariable results and should be carefullyevaluated if considered at all.

• Responses to supplements depend onthe level of feeding, plane of nutrition,stage of lactation and the period ofunderfeeding.

• It is very difficuit to provide short-termrecipes to absolute levels of milkcomposition due to the complexinteraction involved.

• Proper feeding from one lactation tothe next is the simplest and mosteconomic way to achieve high yieldand composition levels in milk—afterall, this is the road to high levels ofprofitable production.

Transition feeding

What is transition feeding?

cereal grains and other additives in additionto the forage.

What changes does the cowundergo during this period?

• The cow will have a change in rationfrom a pasture or forage based dietwith no supplement to a ration whichcould contain cereal grains and otheradditives.

• The cow will calve; this causesphysical trauma and many hormonalchanges, which can affect the cow’sability to fight infection and mobiliseher body reserves of minerals.

• The beginning of lactation will create ademand for greater energy, protein andcalcium requirements by the cow’smetabolism. This demand can be twiceor more than that needed before thestart of lactation.

• The dry matter intake of the cow willbegin to decrease about two weeksbefore calving because of theincreasing size of the calf in theabdominal cavity compressing therumen. The decreased dry matterintake will continue for at least two tothree weeks after calving.

How important is the transition

Transition feeding is when we feed thedairy cow from three weeks before shestarts lactation to up to three weeks aftershe has commenced milking. During thisperiod, the cow has progressed from aheavily pregnant dry cow on pasture orother forages to a fully productive milkingcow consuming a ration which can include

period?

Dry cows are usually considered theuneconomic members of the dairy herd. Inthe past, they have been grazed on thepoorest pasture and are ‘forgotten’ by thefarmer until they calve and start payingtheir way again.

The period around calving is whenmany farmers see most of the commondisease problems in their herd. Thesediseases include:

• downer cows

• calving difficulties or dystocia


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• milk fever

• ketosis

• laminitis (lame cows)

• retained afterbirths

• clinical mastitis

• udder oedema (‘slaking’ of the udder)

In many cases, it is the best producersin the herd which are the worst affected.This group of cows may also be the mostdifficult group to breed and the last cowsto become pregnant.

Many of the above problems can beprevented by proper management andfeeding of the dry cow, especially duringthe transition period. It has already beendiscussed in the Body Condition Scoringsection that cow should be dried off at acondition score of 5 and be fed to retainthis condition score till calving. Thismeans a change in philosophy for manyfarmers. The ration of the dry cow has tobe formulated with the same care as thatof the milking herd.

pregnant cow could result in an increasein milk production of up to 10% in thenext lactation. The extra UDP replacesthe need for the cow’s protein reservesto be used for her growth and her fetus’sgrowth needs.

• The dry cow should be introducedgradually to the milking cow rationstarting about three weeks beforecalving. This ration should not containany additive such as buffers (sodiumbicarbonate, magnesium oxide). It willtake approximately three weeks for therumen microbes to adapt to the changein the ration. There will be lessdigestive upsets, resulting in a furtherdecline in dry matter intake, and betterfeed digestion when the cow startseating the milking cow ration aftercalving.

• The precalving ration should be low incalcium. The cow will be able tomobilise calcium from her skeletonafter calving when her demand forcalcium increases with the onset ofmilk production. If the cow was fed adiet high in calcium, she is less able toreadily mobilise her calcium reservesand could develop low blood calciumand ‘droopy’ or ‘sad’ cow syndrome orelse be a downer cow with clinicalmilk fever.

• Feeding a ration which promotes aslight metabolic acidosis in the bloodcan also enable the cow to mobilisecalcium from her skeleton when sheneeds it. The metabolic acidosis iscreated by increasing the number ofnegative ions in the ration. Theminerals in the ration have bothpositive and negative changes. Thebalance between the positive andnegative charges in the ration is calledthe dietary cation-anion balance orDCAB. Sodium and potassium providemost of the positive charges whilst

What is involved in transitionfeeding?

• The decreased dry matter intake 2weeks before calving means that thecow will need her energy, protein andmineral requirements in a morenutrient dense ration (greater drymatter percentage). This aim may notbe a major problem to achieve in thedry cow before calving because of herlower requirements but it will pose achallenge after the cow has calved andhas began producing milk. The earlylactation cow may not reach fullappetite until 6 to10 weeks intolactation.

• UDP should be added to the earlylactation ration and has been shownthat added protein containing 36 to40% of UDP to the ration of the heavily


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chlorine and sulphur provide most ofthe negative charges.

The DCAB of a ration is calculated as:(% sodium/0.023) + (%potassium/0.039) –

(%chlorine/0.035) + (%sulphur/0.016)

specific transition cow rations which arein the correct DCAB to prevent many ofthe disease problems which occur aroundcalving. The advantage of these rations isthat they are ready to feed without the needfor extensive testing of rations for mineralcontent, which can be difficult if pastureforms part of the ration. The disadvantagesof using these rations include the cost ofthe ration which would be in excess oftraditional dry cow rations and the changein management necessary to feed theration. The dry cows may need to beseparated into different groups so that the‘close-up’ cows are able to be fed theration. This may involve the separation ofexisting paddock and the provision of feedtroughs and hay feeders. However, thereduction in disease problem in the earlylactation period, especially milk fever andretained afterbirth, would result in reducedtreatment costs and reduced labour costs,which are normally required to managethe affected cows.

The percentage of these minerals in allcomponents of the ration, includingpasture, other forages and all supplements,have to be calculated to determine thisbalance. It is not sufficient to just look atthe supplements.

Pastures that have been fertilised withpotash will contain high percentages ofpositive charges such as potassium. Whenusing these rations, the slight negativebalance is created by the addition ofanionic salts to the ration. The anionic saltsinclude magnesium sulphate (epsom salts),ammonium sulphate, ammonium chloride,calciumchloride and calcium sulphate. Onemajor disadvantage in feeding anionic saltsis that cows usually find them unpalatable.

Several feed companies have developed


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Appendix 1: Measuring dry matter

You can use a microwave oven to measurethe dry matter percentage of your feed.The method is easy, although it is timeconsuming. You need accurate kitchenscales that can measure to one tenth of agram, a knife or scissors to chop theforage into small pieces, a brown paperbag and a glass of water.

When you collect your pasture, hay orsilage sample, make certain it represents atrue sample of what the cows are eating. Ifthe pasture is ryegrass with 30% clover,make certain the sample is of the samecomposition.

1. Weigh the paper bag on the kitchenscales.

2. Chop up about 75 g of forage intocentimetre lengths and put this into thepaper bag.

3. Weigh the paper bag with thesample. This is the wet sample.

4. Put the paper bag and the glass(which should be three quarters full ofwater) into the microwave.

5. Microwave the bag and sample for 4minutes. Let the sample stand for 4minutes.

6. Weigh the bag and sample.

7. Microwave for another minute.Make certain the glass of water is stillthree quarters full. Refill if necessary. Letthe sample stand for one minute.

8. Weigh bag and sample.

9. Repeat steps 7 and 8 until there areno further changes in weight.

Calculate the results as follows:Wet sample weight

= weight of wet sample plus bag (step 3)

minus bag weight (step 1).

Dry sample weight

= final weight of bag and sample minus bag weight.

Dry matter percentage= dry sample weight × 100.

wet sample weight


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Potassium

Potassium is involved in water balanceand acid–base balance, as well as musclefunction. It is involved in the manufactureof protein. Mature forages have lowlevels.

Excess potassium fertiliser can causeudder oedema and milk fever.

Deficiency of this mineral is unlikely

Appendix 2: Minerals & vitamins for thelactating cow

Macrominerals are needed in largeamounts. The important ones are:

Calcium (Ca)

Phosphorus (P)

Magnesium (Mg)

Potassium (P)

Sodium (Na)

Chlorine (Cl)

Sulphur (S)

Microminerals are needed in smallamounts. Those important to dairy cowsare:

Cobalt (Co)

Copper (Cu)

Iodine (I)

Iron (Fe)

Manganese (Mn)

Molybdenum (Mo)

Selenium (Se)

Zinc (Zn)

Vitamin deficiencies are rare inAustralia. Those that could potentiallycause problems are:

Fat soluble vitamins

Vitamin A

Vitamin D

Vitamin E

Water soluble vitamins

Vitamin B1 (thiamine)

Vitamin B3 (niacin)

Vitamin B12 (cyanocobalamin)

Biotin

Folic acid

Macrominerals

Calcium

Calcium is required for bone formation,muscle action, milk production andgeneral body function. There are lowlevels in grains, and as all plants age thelevels decrease.

Deficiency can cause milk fever,displaced abomasum (where theabomasum moves to the left hand side ofthe abdomen and becomes compressed bythe rumen) and retained afterbirth.

Phosphorus

Phosphorus is required for boneformation, milk production, energymetabolism and general body function.Grains have higher levels that grass, but asall plants mature the levels decrease.

Deficiency can cause low fertility andmilk yield as well as poor appetite.

Magnesium

Magnesium helps in many enzymeprocesses in the cow and is needed byrumen microbes to grow.

Low levels in lush pastures can causegrass tetany. Low levels in the blood caninterfere with calcium absorption andcause milk fever.


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Iron

Iron is an essential component ofhaemoglobin in the blood, and of theimmune system.

Deficiency rare in grazing cattle; allfeed sources are generally adequate, butanaemia occurs in milk-fed calvesoccasionally.

Iodine

Iodine is found in the thyroid hormonesthat control energy, metabolism, growthand development, and skin and hairformation.

Deficiency can occur in calves as agoitre (lump in the neck) or in cows asreproductive failure.

Supplement with potassium iodide inthe feed.

synthesise vitamin B12. It is essential forthe production of propionic acid which isthe precursor of glucose.

Cattle do not store large amounts ofcobalt, so vitamin B12 production relieson a steady supply of cobalt in the ration.

Deficiency signs include reducedgrowth rate, especially in young animals.,rough coat and ill thrift that does notrespond to worming or improved ration.

Supplementation is usually by cobaltbullets in the rumen.

Copper

Copper is needed for the enzymes thatcontrol energy metabolism, pigmentationand blood formation.

Deficiency signs include weight loss,diarrhoea and a pale rough coat, andinfertility. High molybdenum levels willcause a copper deficiency.

Supplement with copper oxide (as anaddition to the ration or as a rumen bolus)or copper sulphate which can be added tothe water or given as a drench.

in grazing dairy cows.

Sodium

Sodium is essential for the nerves and forthe water and acid–base balance.

Deficiency is uncommon.Signs of low sodium are salt cravings,

loss of appetite and body condition, andincreased nervousness.

Most supplement contain salt in the diet(approximately 1% of the ration).

Chlorine

Chlorine is also needed to ensure a propersalt or acid–base balance in the animal. Itis also needed for stomach secretions.

Supplement with salt in the ration orsalt licks. Deficiency is uncommon.

Sulphur

Sulphur is needed by both the cow andrumen microbes to make essential aminoacids. It is involved in many bodyfunctions.

Some B vitamins contain sulphur.There are significant interactions betweensulphur, copper and molybdenum whenhigh pasture sulphur and molybdenumlevels prevent copper uptake.

Sorghum based diets (including sudan,sudax and other sorghum hybrids) areusually deficient in sulphur.

Sulphur can be supplemented in thefeed or provided to the cows by a mineralblock.

Microminerals

Note: It is best to seek professional advicefrom a veterinarian or other farm adviseron the dose rates for these micro minerals.Excess amounts of these substances cancause toxic signs in cattle and may result indeath.

Cobalt

Cobalt is needed by the rumen microbes to


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Use ferrous sulphate or ferrous chlorideto supplement.

Manganese

Manganese is involved in fat and proteinsynthesis, brain metabolism and variousenzyme systems. Deficiency can reducefertility and cause cystic ovaries andimpaired growth or skeletal and birthabnormalities.

Supplement with manganese oxide ormanganese sulphate.

Molybdenum

Molybdenum is mainly required for thefunction of the enzyme xanthine oxidase,which is involved in excretion.

Very high and very low levels ofmolybdenum affect the metabolism ofcopper. Cattle grazing high molybdenumpastures may show signs of copperdeficiency.

There may be high levels ofMolybdenum in plants grown on high pH(alkaline) soils.

Selenium

Selenium prevents white muscle disease;it has an enzyme function in protectingcell membranes from damage byoxidation. It also important in maintain aneffective immune system.

Selenium deficiency often occurs withvitamin E deficiency. Signs are poorreproduction, retained placenta, mastitisand general ill thrift.

Supplement with selenium bullets,drenches or sodium selenate in the feed.

Zinc

Zinc is involved in many body functionsin the cow. It activates 30 differentenzymes and enhances the action of thereproductive hormones.

Deficiency symptoms include reducedfeed intake, feed efficiency, stiff joints andcystic ovaries. In feed lot cattle, zinc

supplementation may be helpful inpreventing foot problems.

Supplement with zinc oxide, zincsulphate or zinc methionine.

Vitamins

Vitamins A, D and E

Vitamin a has numerous functions,including maintenance of the skin andother tissues and prevention of nightblindness.

Vitamin D mainly acts to help calciummetabolism.

Vitamin E has a similar role toselenium and helps the immune systemand muscle formation.

B vitamins

Vitamin B1 (thiamine) can be synthesisedin the rumen, but feedlot cattle canbecome deficient and need thiamineinjections.

Niacin can help with energymetabolism for preventing ketosis, but itcan be costly. Some rations containinghigh percentages of fat may include niacinto maintain rumen function.

For vitamin B12 see cobalt.


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Further information

Agriculture Victoria 1994, Dairy CowNutrition Manual, Victorian Departmentof Agriculture, Melbourne

Cole, V. G 1981, Guide to Fodder Cropsfor Livestock, Macarthur Press, NSW

Kellaway, R. & Porta, S. 1993, FeedingConcentrates: Supplements for DairyCows, Dairy Research and DevelopmentCorporation, Glen Iris, Victoria

Post Graduate Foundation in VeterinaryScience 1991, Dairy Cattle Production,Proceedings No. 161, Post GraduateFoundation in Veterinary Science, Sydney(phone 02 9264 2122)


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realistic rations · v introduction section 1 understanding the dairy cow and her feed 1.1 aims of...

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