LECTURE 20FEEDLOT CATTLE NUTRITION

pp. 409-418

GOALS WHEN FEEDING FINISHING CATTLE

• Maintain animal health• Produce a desirable carcass

– Choice grade (5.0 to 8.5% intramuscular fat, 28% body fat)• Body weight will vary with genetics, growth rate, and implants

– Yield grade 3 or less– Acceptable maturity (< 30 months)– White fat and bright red muscle– Carcass weight between 600 and 900 lbs

• Minimize production costs– Feed– Non-feed costs (Facility depreciation, Interest etc)

• Minimize environmental impacts– Maximize feed efficiency

TRADITIONAL SYSTEM OF FEEDLOT FINISHING OF BEEF CATTLE

Feeder calf or yearling (600-900 lb)

Feed high grain diet (80-90% grain) with ionophore

Implanted with estrogen w/ or w/o Trenbolone acetate

Gain 3-4 lb/dayFeed/gain 6-7

Harvested at 1200 –1400 lbproducing a carcass with achoice quality grade and ayield grade of 2 or 3

Season prices:High in March and AprilLow in July

FEED INTAKE OF FEEDLOT CATTLE• Normal intake is 2 to 3% of body weight• Factors

– Degree of finish as affected by body weight, cattle type, implants etc.

– Feeding after a period of restricted gain (backgrounding or grazing)• Part of compensatory gain

– Diet• Ionophores• Forage concentration• Fat concentration • Nutritional imbalance

– Potassium deficiency– Environmental

• Temperature (base is 15 to 25 C)– Decreases by 10 to 35% if temperature increases to 35C– Increases by 16% is temperature decreases to -5 to -15C

• Mud – Decreases by 15% if mud depth is 4 to 8 inches

EFFECT OF BODY WEIGHT AND FATNESS ON FEED INTAKE

Body fat

DMI

• Maintenance energy requirement of finishing beef cattle– NEm, Mcal/day = .077BW.75

– Modified by a large number of factors

– Maintenance ModifiersModifier Modification Change in NEm reqt.Breed Beef breed Base

Dairy breed Increase by 20%Brahman breed Decrease by 10%

Sex Bull Increase by 15%Previous nutrition

BCS<5 Decrease by 5%/BCS unit ( Another part of

compensatory gain)BCS>5 Increase by 5%/BCS unit

Environmental stress

Cold temp, dry coat, BCS 5

Increase by 15%

(Include temp, wind, BCS, hide & coat thickness, coat cover and heat increment)

Cold temp, dry coat, BCS 4

Increase by 20%

Cold temp, snowy coat, BCS 5

Increase by 96%

Heat stress Increase by 11 to 25%

EFFECTS OF BODYWEIGHT ON THE NEm and NEg REQUIREMENT TO GAIN 3.5 lb/day FOR STEERS AT EITHER AT FINISHED WEIGHT OF 1200 OR 1400 LB

ENERGY SOURCES FOR FEEDLOT DIETS• Grains

– Fed at levels up to 95% of the diet– Usually are processed

• Grinding, cracking or rolling• High moisture corn• Steam-flaking

– Cattle must be properly adapted to diet– Limits

Grain Maximum fed, % of DM ConsiderationCorn grain 92

Milo 92Wheat 50 Highly fermentable

starch

Oats 25 High fiber, low energyGround ear

corn95

(If no forage fed)High fiber

• Grain processing byproducts

• Fat supplements (Tallow, Vegetable-Animal Fat)– Increase energy concentration– Reduce dustiness– Limit to 5% of DM

• Molasses– Increase energy concentration– Reduce dustiness– Increase palatability– Increase binding of pellets– Limit to 5% of DM

Grain byproduct Maximum fed, % of DM Consideration

Distillers dried grains w/ solubles (DDGS)

40 High sulfur, High fat

Corn gluten feed 20-30 High fiber

Distillers solubles 20 (If DDGS not in diet)

High sulfur, high fat

Soy hulls 25 High fiber

ADAPTATION TO HIGH GRAIN DIETS• Rumen microbial population must be slowly adapted

to high grain diets to prevent:– Lactic acidosis– Founder– Polioencephalomalacia– Bloat

• Systems– Hand feeding

• Cattle fed forage for 4 to 7 days• Start feeding grain at 0.5% BW • Amount of grain increased at 1 lb/day to 1% of BW• Amount of grain increased at 1/2 lb/day to full feed• Decrease forage as grain increased• Feed bunks must be monitored to ensure feed

consumption– If intake decreases or ceases, slow rate of increase

– Self-feeding a mixed ration

– Supplementing Vitamin A at 30,000 to 50,000 IU/hd/day and Vitamin E at 400 to 800 IU/hd/day can assist in managing stress

Days Roughage:Concentrate1-4 100% hay5-8 50:50

9-13 40:6014-17 30:7018-21 20:8022-25 15:85

26 10:90

MEETING THE FIBER REQUIREMENTS OF FEEDLOT CATTLE

• Need for fiber in ruminant diets– Stimulate rumination and saliva secretion– Prevents

• Parakeratosis of rumen wall• Liver absess• Acidosis• Bloat

• Requirement is for effective NDF (eNDF)– Includes fiber content and physical form of fiber

• Requirements– 8% eNDF if:

• Good bunk management, ionophore fed– 20% eNDF if:

• Variable bunk management, no ionophore

• eNDF concentrations of common feeds in feedlot diets– Feed eNDF, % of DMGround corn stalks 65Ground hay 51Corn silage 33Soy hulls 22Corn gluten feed 13Whole corn grain 10Cracked corn 8Ground corn 5Distillers dried grains w/solubles 4Soybean meal 3

• Metabolizable protein supply dependent on:– Ruminally undegraded protein – Microbial protein synthesis

FACTORS AFFECTING THE PROTEIN REQUIREMENTS OF GROWING BEEF CATTLE

• Animal age and weight• Compensatory gain • Use of hormone implants• Feed intake

PRACTICAL IMPLICATIONS OF MP REQTS. OF FINISHING BEEF CATTLE

• Cattle at light weights relative to finishing weight will benefit from sources of rumen undegradable protein– Distillers grains w/solubles– Corn gluten meal– Expeller processed soybean meal– Blood meal

• Cattle at moderate weights only need to be supplemented with rumen degradable protein sources– NPN

• Recall rules for safe use of NPN• Cattle near finishing weights obtain adequate

metabolizable protein from a corn-corn silage diet with no protein supplementation

• If DDGS are fed at 20 to 40% of the DM at any time during feeding, no protein supplementation is necessary

MINERAL NUTRITION OF FEEDLOT CATTLE• Salt (NaCl)

– Should be supplied at 0.25% of diet DM• Calcium and phosphorus

– Feeds commonly used for feedlot diets contain low amounts of CA and adequate to high amounts of P

– Add limestone to maintain Ca:P ratio of 2:1• Prevents urinary calculi

• Potassium– Borderline on high grain and corn silage diets– Monitor and supplement if:

• Low feed intake• Heat stress

Ca, % of DM P, % of DMReqt 0.4 – 0.6 0.24 – 0.30

Corn grain 0.03 0.32Corn silage 0.25 0.22

DDGS 0.26 1.0

• Sulfur– Toxic is fed at greater than 0.4% of diet

• Causes polioencephalomalacia• Occurs at lower dietary levels of S if S content of water

is high– May be a problem in diets containing high levels of Distillers

dried grain w/ solubles• DDGS contain as much as 1.0% S

– Management• Do not feed > 40% DDGS in cattle diets• Increase forage content of diet (15%)• Delay addition of high levels of DDGS until cattle

adapted to grain• Use DDGS from plants that contain consistent levels of

S• Supplement cattle fed DDGS with 150 – 200 mg

thiamine/day• Trace minerals

– Cu, Zn, Fe, Mn, Co, and I should be supplemented in a premix

VITAMIN NUTRITION OF FEEDLOT CATTLE• Vitamin A

– Supplement at 30,000 – 50,000 IU/d during adjustment– Supplement at 20,000 – 30,000 IU/d after adjustment

• Vitamin E– Supplement at 400 – 800 IU/d for first 30 days in feedlot– Supplement at 500 IU/d during last 100 days in feedlot will

improve product shelf life• Vitamin D

– No need for supplementation if exposed to sunlight• B vitamins

– Thiamine supplementation at 150 – 200 mg/d may reduce the risk of polioencephalomalacia in cattle fed DDGS

– Other B vitamins not needed

FEED ADDITIVES AND IMPLANTS FOR FEEDLOT CATTLE

Class Products EffectsFeed

additivesIonophores Monensin,

Lasalocid, Salinomycin

Increase propionic acid and decrease methane production in

rumen, decrease feed intake, increase feed efficiency, increase

ADG in cattle on high forage diets

Progestogen Melengesterol acetate (MGA)

Prevents estrus in heifers, increase ADG and feed

efficiencyB-agonist Ractopamine

(Optiflex), Zilpaterol (Zilmax)

Fed during last 28 – 42 days in feedlot. Increases ADG, feed efficiency, ribeye size

and retail meat yieldImplants Estrogen Estradiol Increase rate of gain, feed

efficiency, and protein gainProgestogen ProgesteroneAndrogens Trenbolone

acetate