animal response to drought: drought management on range and pastureland

8/9/2019 Animal Response to Drought: Drought Management on Range and Pastureland

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ACKNOWLEDGEMENTS

Many suggestions from range livestock producers and agency personnel in Nebraska and South Dakota wereincorporated into this handbook. We would like to recognize the following individuals for their helpful and constructive

reviews of draft manuscripts:

Daryl Cisney, Ogallala, NE Floyd Reed, Chadron, NE

Roger Dunn, Mission, SD Greg Reeves, Rapid City, SD

David Fischbach, Faith, SD Sid Salzman, Ainsworth, NE

Jan Joseph, Valentine, NE John Samson, Lincoln, NE

Rick Rasby, Lincoln, NE Clair Stymiest, Rapid City, SD

We are also indebted to the following faculty members for their comprehensive review of the final draft:

Lowell Moser

Department of AgronomyUniversity of Nebraska-Lincoln

Pat Johnson

Department of Animal and Range Sciences

South Dakota State University

Don WilhiteInternational Drought Information Center

University of Nebraska-Lincoln

The authors express their most sincere appreciation to Jean Haas for her tireless assistance in the preparation of thishandbook. Her dedication, tenacity, and typing skills were invaluable contributions.

Financial support for the development and publication of this handbook was provided by

Renewable Resource Extension Act funds through the University of Nebraska and South

Dakota State University. Financial support was also provided by the Nebraska Range

Management Cooperative Committee.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 19 14, in cooperation with theU.S. Department of Agriculture. Kenneth R. Bolen, Director of Cooperative Extension, University of Nebraska,

Institute of Agriculture and Natural Resources.

Cooperative Extension provides information and educational programs to all people without regard to race, color, national origin, sex or handicap.


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PR INC IPLE AUTHOR S

Patrick E. Reece, Jack D. Alexander III and James R. Johnson3Range Management Extension Specialist

2Extension Range ManagerUniversity of Nebraska Panhandle Research and Extension Center

4502 Ave I

Scottsbluff, Nebraska 69361

3Range Management Extension SpecialistSouth Dakota State University

West River Agricultural Research and Extension Center

801 San Francisco Street

Rapid City, South Dakota 57701

CONTRIBUTING AUTHORS

Don C. Adams, UNL, North Platte, Nebraska

Bruce E. Anderson, UNL, Lincoln, NebraskaJames T. Nichols, UNL, North Platte, Nebraska

James G. Robb, UNL, Scottsbluff, Nebraska

Ivan G. Rush, UNL, Scottsbluff, Nebraska


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TABLE OF CONTENTS

PAGE

INTRODUCTION ..............................................................................1

Historical Perspective ..................................................................1Early Ecological Observations of Drought.. .................................. 1

PLANT RESPONSE TO DROUGHT ..............................................2

Plant Response to Grazing ..........................................................3

Value of Plant Cover....................................................................4

Influence of Range Condition ......................................................4

MANAGEMENT PREPARATION FOR DROUGHT . . . . . . . . . . . . . . . . . . . . 5

HERD MANAGEMENT ....................................................................6

Past and Future Stocking Rates ....................................................6

ANIMAL RESPONSE TO DROUGHT ............................................7

Supplementation ..........................................................................8

Toxicity Associated With Drought ................... ........................... 9

PREDICTING FORAGE PRODUCTION ANDSTOCKING RATES ........................................................................10

Site Specific Decision Tools ......................................................10

Yield After Prolonged Soil Moisture Shortages .......................... 12

Using Annual Forages ................................................................12

DROUGHT MANAGEMENT PLANS .......................................... 15

Questionable Practices ..............................................................16

RANGELANDRESOURCEINVENTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

GRAZING MANAGEMENT ..........................................................18

Capitalizing on Weed Forage Resources .................................... 18Skim or Flash Grazing ..............................................................19

Optimizing Forage Production .................................................. 19PLANT RECOVERY AFTER DROUGHT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

APPENDIX ......................................................................................21

Share Arrangements ..................................................................21

Tax Rules for Drought Induced Sale of Livestock ...................... 21

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

RECOMMENDED EXTENSION PUBLICATIONS . . . . . . . . . . . . . . . . . . . . 23


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A Drought Management Handbook for Range and Pastureland

in Nebraska and South Dakota

Drought is generally defined as a

prolonged period during which annualprecipitation is less than 75 percent of

average. Based upon this definition,drought has occurred in 21 percent ofthe years in the northern Great Plains

since 1940 (Holechek et al. 1989).

Poor distribution of precipitation in asingle year or less than average precip-

itation in successive years can also

cause drought conditions.

Drought is a major factor in rangemanagement. In any given year, range-land vegetation is either in the recov-

ery phase or under the direct influence

of drought. Drought causes long-term

effects and recovery is a long-termprocess. Management strategies mustprovide plants with opportunities to

maintain or improve vigor.Stocking rate is the most impor-

tant tool for grazing management, es-pecially under drought conditions.

There are no tricks to compensate forovergrazing. Stocking rates for indi-vidual pastures should be based upontarget levels of defoliation for key spe-

cies. As range condition increases therelative effects of drought decrease.

The most effective method of droughtmanagement is preparation in the

years preceding drought. The best timeto begin preparation is now.

Drought will always be a nemesisfor the range livestock industry, espe-

cially for ranchers who become com-

placent during wet cycles. Ranchers

need to capitalize on above average

levels of forage produced in good

years, but timely adjustments must be

made to balance livestock require-

ments with available forage and feed

resources when drought occurs. Man-agement flexibility is critical for

survival.

The fundamental objectives ofdrought management are to (1) mini-

mize damage to rangeland resources

during and after drought and (2) mini-

mize economic loss. Ranchers who

achieve both of these objectives can

quickly capitalize on additional forage

in good years. Damage to forage and

land resources is reduced and potentialprofit is increased when ranchers make

timely decisions.

Ranchers can benefit from thesubstantial amount of informationgained during past droughts. Numer-ous alternatives for the development of

drought management plans are dis-cussed in this handbook. Crisis deci-

sions can be avoided with timely eval-

uation of alternatives and implementa-

tion of sound drought managementplans. Success depends upon viewingdrought as a normal part of the range

livestock production environment, not

as a catastrophic event.

Historical Perspective

The unpredictable yet certain

recurrence of drought is the majorfactor limiting the use and develop-

ment of resources in the Great Plains

(Schumacher 1974). Wet and drycycles have had an impressive effecton land prices, population, and govern-ment programs in the Great Plains. In

the 1890s droughts caused emigrationfrom affected areas. Emigration from

areas affected by recent droughts hasbeen limited because intervening

government programs have reduced

the economic impact of drought.

The Agricultural AdjustmentAdministration (AAA), the Soil

Conservation Service (SCS), and statesoil conservation districts were

established during the drought of the

1930s. Tracts of land deemed sub-

marginal for cultivation were pur-

chased by the federal government to

remain in grass or to be reseeded to

grass. These lands have been admini-stered by the U S Forest Service since1954 as national grasslands. Legisla-

tion authorizing the Soil Bank Pro-gram and the Great Plains Conserva-

tion Program was passed during the

drought of the 1950s. These programs

were to bring about more permanent

solutions to problems resulting from

drought and the cultivation of landunsuited for crop production.

-l-

During periods of optimismbetween drought, many people becameconvinced that the climate had

changed and would be better. In thedays of early settlement, land promot-ers and spokesmen for the railroadsclaimed that, rainfall follows the

plow. Although this concept had noscientific basis, the myth persisted for

years. During wet cycles or periods of

favorable commodity prices, land

values have increased and additionalrangeland has been broken andfarmed. For example, from 1974

through 1977 approximately 690,000

acres of rangeland were plowed for

crop production in South Dakota.Droughts in the Great Plains are

associated with abnormal atmospheric

circulation patterns caused by several

factors including sunspot cycles andsurface temperatures of the PacificOcean. However, while the probability

of a drought can be determined,meteorologists are not yet able topredict a severe drought in advance.

Consequently, drought contingencyplans need to be a part of each yearsoverall management plan.

Early Ecological Observations of

Drought

Dramatic shifts in species compo-

sition and productivity of native grass-

lands were documented in the GreatPlains during and following the major

drought of the 1930s. Drought

depleted surface soil moisture in 1930

and 193 1, but had little effect on the

deeply rooted prairie vegetation. The

summer of 1934 was described by

Weaver (1968) as the greatest drought

ever recorded in the true prairie. As

the dry conditions continued, the

impacts became more severe andpersisted until 1941.

Species composition changed

dramatically as the drought pro-

gressed. As the least drought tolerantspecies died, openings began to appear

in the tallgrass prairie (Weaver 1968).Big bluestem, indiangrass, prairie


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dropseed, and little bluestem gave wayto dense patches of annuals such aspepperweed and six-weeks fescue.

Between 1930 and 1935, 36 to 75

percent of the basal area of all peren-nial plant species was lost on tallgrassprairies in Nebraska and Kansas.

Plants common to more arid

environments, such as western wheat-grass, blue grama, and buffalograss,increased as dominant tallgrass prairiespecies declined (Weaver 1968).

Western wheatgrass, which was ini-tially a minor component of the tall-

grass prairie, became a dominantspecies as the grasslands deteriorated.

Early spring growth, prolific seedproduction and ability to migrate into

new areas by means of long, slenderrhizomes provided western wheatgrass

with tremendous competitive advan-

tages for limited soil moisture(Weaver 1968). By 194 1, large areasof the tallgrass prairie were dominated

by western wheatgrass.The boundaries between the major

vegetation types in the Great Plainsshifted eastward as a result of the

drought. After seven years of deficientsoil moisture the mixed prairie zone

had moved l00-150 miles eastwardinto what was previously tallgrass

prairie (Weaver 1943). Even withoutgrazing, much of the mixed prairie

type vegetation was reduced toshortgrass plant communities (Al-

bertson and Weaver 1946).From 1933 to 1935, soil water in

the mixed prairie of western Kansas

was exhausted beyond the depth of

little bluestem root penetration (Al-bertson 1937). Where initially inter-

mixed and in competition with

shortgrasses, 90 to 100 percent of littlebluestem plants died. Although more

deeply rooted, sideoatsgrama and big

bluestem also suffered losses, butmade some recovery during intermit-

tent periods of favorable growingconditions. Shortgrass prairie domi-

nated by blue grama and buffalograss

suffered relatively small losses when

ungrazed, although several species of

forbs disappeared entirely. Rapidstolon growth allowed buffalograss to

quickly reclaim bare areas whenmoisture conditions improved tempo-

rarily. Consequently, basal cover of

buffalograss more than doubled insome years during the 1930s. Nativedrought resistant shrubs and forbs with

spreading or very deep root systems

also increased during the greatdrought. Species that commonlyincreased included broom snakeweed,

snowberry, heath aster, goldenrod,

western ragweed, and scarlet globe-mallow.

When intermittent precipitationdid occur, the growth of large numbers

of opportunistic annuals caused a

dramatic change in the appearance ofrangeland. Areas which had been

covered by wind-blown soil and were

devoid of perennial vegetation wereideal germination sites. Seeds werespread by wind throughout the GreatPlains. Consequently, most prairies

were infested with lambsquarters,

pigweed, stinkgrass, ticklegrass, greenfoxtail, buffalo burr, pepperweed,Russian thistle, downy brome, and

little barley. Weaver (1968) statedthat, so abundant were the weeds thatthe prairies often appeared more like

abandoned fields than grasslands.

The drought of the 1930s wasended by favorable precipitation in1940 and 194 1 and yield of perennial

grasses increased dramatically (Al-

bertson and Weaver 1944). However,

annual weeds also produced a substan-tial amount ofherbage in 1940 and1941 because of drought caused

reductions in perennial plant cover.Although major changes in prairievegetation had occurred during thedrought, remnants of most species sur-

vived (Weaver and Albertson 1943).After intensive investigation of theeffects of serious droughts in the

1930s and 1950s, Albertson et al.

(1957) concluded:

Presumably native vegetation

developed under conditions similar to

these, and it is also safe to assume that

native plants will continue to dominate

the prairies if not continuously

overgrazed by livestock or buried too

deeply by soil blown from cultivated

fields. Therefore, if our nativ e v egeta-

tion is completely destroyed, man

should be held accountable.

PLANT RESPONSE TO DROUGHT

Understanding how moisture

stress affects plant physiology isessential when designing drought

management practices. Native prairieplants are well adapted to low and

variable precipitation. However,

substantial reductions in plant cover

and vigor occur under serious, pro-longed drought. Initial growth after

winter or summer dormancy isproduced with stored energy reserves.

Short flushes of growth terminated bydrought, grazing, hail or frost often

deplete energy reserves and reduceforage production the following year.Plant survival during dormancy

depends totally upon energy reserves.

Plants must rely on stored energy forlong periods of time when drought-

induced summer dormancy is added to

winter dormancy.

Drought reduces both root andshoot growth. Extensive root systems

-2-

are critical for the use of limited soil

moisture supplies even in an averageyear. More than 50 percent of the roots

in grass plants die each year, evenunder average conditions. If leaf

growth is limited, adequate carbohy-

drates will not be available for root re-

placement. Consequently, substantialreductions in root production can

occur under drought conditions whenhealthy root systems are most critical.

Each years forage crop isproduced by a new set of tillers that

develops from buds located in thecrown or on rhizomes or stolons.These buds are the mechanisms for

growth. The degree to which drought

impairs a plants potential for future

forage production depends upon thestage of plant development at which

growth stops. Reduced plant growthunder drought conditions or excessive

grazing before grasses head may


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Figure 1.

PERCENT

DEFCUATKN

ILN 4 N 2N 4w

STWELE ISXHT1666 1967

HEADED

REMWEDBY

PERCENT

MFUUTKM

-2N 4 N 2N 4N

STUBBLE MIGHT1966 1987

-

Herbage yield and the amount of herbage removed in 1986 when individual

needleandthread plants were clipped at a 2 or 4 in. stubble height. Plants wereclipped only once on May 15 (late boot stage) or on June 15 (fully headed stage).Total herbage production was measured one year after clipping. Precipitationwas above average in both years.

reduce or eliminate formation of newbuds. Fortunately, buds in perennialgrasses can be carried over from the

preceding one to three years. Althoughthe total number of buds available fornext years tiller production is often

reduced by drought, the presence ofsome buds from preceding years

allows perennial grasses to producetillers the following year.

Plant Response to Grazing

Many native, perennial grasses are

most sensitive to heavy defoliation

from the late boot to early headingstage. Heavy grazing during a single

growing season will reduce forage

production in following years. Reduc-

tions in forage can be dramatic evenwhen growing conditions are favor-

able. The following conclusions weredrawn from a study in which

needleandthread plants were clipped attwo stubble heights in western Ne-

braska during two consecutive years(Figure 1). Precipitation was above

average in both years of this study.(1) Heavily defoliated plants

were unable to fully capitalize

on favorable precipitation the

following year.

(2) Needleandthread was moresensitive to heavy defoliationwhen in the late boot com-

pared to the fully headed

stage.The combination of drought and

heavy grazing can cause severereductions in forage production and

plant vigor. Grazing intensity had adramatic impact on the reduction ofperennial plant cover during the

1950s drought (Weaver 1968).

Conditions were the most severe in the

west central part of the mixed prairie.Moderate grazing generally causedlittle change in cover compared to

ungrazed sites. Heavy grazing nearlydoubled the loss of perennial plantcover caused by drought alone.

Proper utilization during the grow-

ing season is generally the removal of50 percent or less of the present, cur-rent year leaf and stem tissue by

weight. A simple procedure can be

used to develop a visual perception ofpercentage forage utilization. Clip thecurrent year growth from random

bunches or tillers at the ground level.

Wrap the samples with string or tape.Balance the sample on your finger.The point of balance is the height at

which 50 percent of the leaf and stem

material would be removed. Clip the

sample at this point and balance eachhalf to estimate heights for 25 and 75percent utilization. Since utilization

often differs across the pasture, youwill need to monitor average height ofutilization throughout each pasture.Estimates of the stubble height at

which a target level of utilization willoccur should be made when the cattle

enter each pasture.Proper utilization will cause little

reduction in root growth and plant

vigor. Grazing in excess of 60 percentwill cause dramatic reduction inamount and depth of root growth

(Figure 2). If drought reduces plant

0 20 4 0 6 0 8 0 1 0 0PERCENTDEFOLIATlON BY WEIGHT

Figure 2. Weight of root tissue in response to degree of defoliation based upon removalof current year leaf and stem biomass (Olsen and Lacey 1988). Maximum rootgrowth (100%) occurs with no defoliation.


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height and seed stalk production,average utilization of key foragespecies should not exceed 50 percent

even after grasses become dormant. It

may be necessary to manage for lowerlevels of utilization to provide enough

remaining plant cover for site stability.

Key species are perennial plant

species that are important forage pro-ducers or have value as an indicator ofrange condition. They are oftendecreaser species that are preferred by

livestock and are generally indicativeof good to excellent range condition.

Common key species are westernwheatgrass, prairie sandreed, and the

bluestems.

Late season or secondary green-up in a drought year is not necessarily

a bonus forage resource. Ranchers

should use secondary green-up with

extreme care. When plants breakdrought induced-summer dormancy,the initial growth will be produced

from meager levels of stored energy,further reducing reserves needed forwinter survival and spring green-up

the following year. While this prin-ciple most often applies to cool season

grasses in the fall, it is also importantin the management of warm seasongrasses following a mid-summer break

in dormancy.

Value of Plant Cover

Grazing management influences

the effectiveness of precipitation.Practices that increase plant cover or

plant vigor lead to an increase in the

amount of precipitation that enters thesoil. Retention of precipitation from

snow or rain increases as plant coverincreases. Plant cover breaks the

impact of rain drops on the soil and isa physical barrier to runoff and wind

related snow loss. As plant vigorimproves, root systems become moreextensive and provide surface open-ings for water movement into the soil

profile. Plant litter and standing plants

reduce evaporation losses by moderat-

ing extremes in soil surface tempera-

tures and by protecting the soil against

drying winds. Removal of all litter

from mixed grass prairie in good to

excellent condition may reduce forageproduction by as much as 60 percent

(Adams 1988).

During the growing season, mois-ture is the most limiting plant growth

factor on rangelands. Manipulation of

plant cover and maintenance ofhealthy root systems are the bestapproaches available for ranchers to

optimize use of precipitation. Over-

grazing or wildlife may cause drought-like conditions even with average pre-cipitation. Dramatic reductions inplant cover can cause severe and long-

lasting modifications of plant environ-ments. Inadequate plant cover can leadto substantial wind or water erosion of

valuable top soil.

Influence of Range Condition

The effects of drought are intensi-fied at lower range conditions. Range-

land in fair condition is more severelyaffected by drought than rangeland ingood to excellent condition. The

diversity of perennial grasses tends toincrease as range condition increases.Increased diversity of species withdifferent growth seasons and rooting

habits increases the number of oppor-tunities for forage production underthe limited and irregular precipitationpatterns characteristic of drought.

As the number of grass speciesincreases, there is a greater opportu-

1 0 0

8 0

0

nity for livestock to select differentgrasses during the growing season.The preference for different grasses by

cattle is strongly influenced by stage

of plant development. Since differentspecies begin growth and mature atdifferent times, livestock tend to select

different grasses as the summer graz-

ing season progresses. Streeter etal .(1968) documented pronounced, sea-sonal shifts in preference by yearlingsteers from needleandthread to prairie

sandreed to blue grama (Figure 3).Under proper stocking, these natural

shifts in preference result in reducedfrequency and intensity of grazing on

individual plants. Because rangelandin fair condition offers a less diverseselection, cattle graze the same species

more frequently over a longer period

of time.

Range condition also influencesthe rate of recovery in forage produc-tion after drought (Hanson et al. 1978).

After drought from 1961 to 1962,pastures in excellent condition recov-ered more rapidly than pastures in fair

range condition from 1963 to 1965 at

Cottonwood, South Dakota (Figure 4).Severe drought in 1966 caused a dra-matic reduction in forage productionregardless of range condition. With

above average precipitation, forageproduction the year following drought

NEEDLEANDTHREAD

PRAIRIEr

- - - \ SANDREED

JUNE JULY AUGUST

Figure 3. Each line represents the percent of steer diets composed of needleandthread,

prairie sandreed or blue grama from early June to late August on a sandsrange site in western Nebraska (Streeter et al. 1968).

-4-


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was much greater on excellent versus

fair condition rangeland in 1967.Pronounced differences in levels ofproduction between condition catego-

ries did not occur in 1968 becausemost of the precipitation occurred afterJune 1. Consequently, the cool season

species which composed 40 percent of

the vegetation on excellent conditionsites were unable to respond. Herbage

production was still greater forrangeland in excellent compared tofair range condition in all years.

The trend in range condition overpreceding years is also important inrange recovery. If the trend is down-

ward, pastures in any condition willhave plants with poorly developed rootsystems and limited protective plantcover before drought. Under these

conditions recovery after drought will

require sound management over anextended period of time. Even withsound management, plant vigor maynot fully recover for 5 or more years ifheavy grazing occurred prior to andduring drought.

I EXCELLENTm FAIR - 1 9_ 1 5

- 6

- 3

0

The influence of range condition and drought on perennial grass and forhproduction on a clayey range site near Cottonwood, South Dakota (Hanson et

al. 1978).

MANAGEMENT PREPARATION FOR DROUGHT

Drought will challenge the mental

toughness of even the best of manag-

ers. Diverse practices can be used tomaintain ownership of cows under

drought conditions. Some ranches willliquidate or relocate part or all of theirbreeding stock. The value of keepingbreeding herds on the ranch must be

weighed against the additional costs

that are probable when drought con-tinues. Recovery of additional produc-

tion costs will depend upon: (1) pro-ductivity of livestock, (2) productivityof rangelands, and (3) livestock market

prices during and following drought.

Several additional questions will helpyou determine how much risk you can

afford to accept:

(I)

(2)

(3)

(4)

(5)

(6)

(7)

What is your current financialposition, including financial

assets and obligations?

What are your short- andlong-term family needs?What are your family and

ranch goals?How secure is your relation-ship with the banker?

Are you prepared to acceptthe additional stress of addedrisk?

How soon must losses

incurred during and following

drought be recovered?

Would you rather risk the lossof the ranch and/or breeding

herd than sell out?

Desperation caused by financial

problems can lead to the use of exces-sive stocking rates that reduce animal

performance and cause dramatic re-ductions in plant vigor. Overgrazedland is also worth less to future buyers

or renters. If serious financial prob-

lems exist before drought, it may be

best to sell before remaining equity islost or additional debt is incurred.Even when range livestock operations

are solvent, it may be prudent to

liquidate or relocate part or all of thebreeding herd to avoid additionalproduction costs or to avoid damaging

rangeland. Under severe or prolongeddrought conditions the cost of replac-ing livestock is almost always less

than the cost of long-term reductions

in rangeland productivity. Additional

considerations are discussed in C225

Ranch Management, a South Dakota

Extension Publication.

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10/27

I HERD MANAGEMENTThe best alternative for drought

management is to reduce total foragerequirements. Reducing stocking ratesduring drought pays dividends in terms

Of:

(1) optimized animal perform-

ance,(2) reduced supplemental and

winter feeding costs,(3) minimized damage to forage

resources, and(4) enhanced range and pasture

recovery following drought.Sell or relocate livestock as soon

as shortages in forage and feedresources are anticipated because

market value tends to be highest at thebeginning of a regional drought. If

additional shortages in forage occur,calculate the additional costs associ-ated with keeping cows on the ranch(feed, interest, labor, etc.) or transport-ing cows to another location with ade-quate feed or forage. If your calcula-tions show an unreasonably high costof producing a weaned calf, it may beprudent to sell or relocate part or all of

the cow herd (See Appendix). The fol-lowing practices can help to minimize

liquidation of the breeding herd:(1) Early weaning can extend

the forage base. By shiftingcows from a negative energybalance while suckling calvesto apositive balance while dry,cow condition can often be

improved or maintained for a

longer period of time. Im-proved cow condition will re-

duce winter feed requirements

and improve conception ratesthe following year. It is usual-ly more economical to weancalves early and to feed cows

and calves separately. Wean-ing calves in mid-Septemberversus mid to late October

could prevent significant

declines in cow condition. It

is also possible to weancalves at an early age, 40 to

80 days, with excellent man-

agement and proper nutrition.

The cost of feeding earlyweaned calves can be high

(2)

(3)

(4)

(5)

(6)

because of the need for high

quality feed. In Nebraskarequest a copy of Manage-ment of Early Weaned

Calves (G83-655) throughyour local Extension office.Practice early and heavy

culling of less productive

cows such as late calving

cows and older cattle.

Remove yearlings from

summer pastures early. Sell

or place yearlings on alternateforages or on full feed in dry-lots as soon as shortages in

range or tame pasture forage

are anticipated (See Appen-dix). Do not hold yearlings onrangeland with supplementalfeed unless you have a cleareconomic reason for doing so.Livestock receiving substituteor replacement feeds shouldbe placed in pens or small

paddocks to minimize dam-

age to rangeland.Consider curtailing produc-

tion of replacement heifers

for one year. The nutritionalrequirements are higher forreplacement heifers than older

cows in the herd especiallyfor wintering. Unless the aver-

age age in the cow herd is high,or there is a sound reason to

cull a large number of cows,the curtailment of replace-

ment heifer production for 1

to 2 years will have little im-

1pact of animal performance in

many commercial operations.

Bulls may need to be supple-

mented earlier than other

classes of livestock to be in

acceptable condition whenthe breeding season begins.

This is especially true for

yearling bulls used for a long

breeding season.

vlaintain a percentage ofhe livestock herd as a read-

ly marketable class oftack, such as yearlings ortackers. Optimum flexibilitys generally obtained when

-6-

the forage requirements of thebreeding herd are equal to 60to 70 percent of the total Ani-

mal Unit Months (AUMs)available from range and pas-tureland resources. Calculatethe amount of required forageand available forage for each

season during a 12-monthperiod to determine the ap-propriate size of the breeding

herd. Assistance in develop-

ing a balanced year-roundfeed and forage program isavailable from the Soil Con-servation Service, US ForestService, and Cooperative Ex-tension. A Guide For Plan-ning and Analyzing A Year-

Round Forage Program (EC

86- 113) is available from the

Nebraska Cooperative Exten-sion. This handbook containsan explanation of standard

procedures for calculatingstocking rates.

Past and Future Stocking Rates

Grazing management during yearspreceding drought is a major factor inrange vegetation response to drought.

Managers may have assumed that nochange in stocking rate has occurred

on their ranches because they have notincreased livestock numbers. Theamount of forage consumed in apasture depends upon animal size aswell as animal numbers and days of

grazing. The average size of cows,

calves, and yearlings has increased on

many ranches over the past IO years.A 10 to 40 percent increase in average

animal weight should be equated to a10 to 40 percent increase in stocking

rate. Inadvertent increases in stockingrates may lead to overgrazing and

reduced plant vigor before drought.All range livestock producers need tocritically evaluate their animal weightsand use an appropriate animal unit

(AU) equivalent when calculating

stocking rates. Under present guide-

lines, each 100 lb of beef animal bodyweight is equal to approximately 0.1

AU. Inadvertent overstocking may

reduce animal performance and willdamage the forage resource.


11/27

ANIMAL RESPONSE TO DROUGHT

Performance of livestock is afunction of nutrient requirements and

intake. Quantity and quality ofavailable forage are primary regulators

of nutrient intake in grazing cattle.Grazing pressure is the relationshipbetween the total quantity of availableforage in a pasture and total daily

forage requirements of livestock at a

given point in time. Stocking ratedecisions regulate grazing pressure andhence forage quantity and quality.

Excessive grazing pressure may occur

under drought even when stockingrates are reduced. Stocking rates areoften expressed in terms of animals/

acre/season. Animals graze forage, not

acres. Therefore stocking rates must bereduced to the level of available forageor animal performance will suffer.

3.0

2.0

z

9Y!4 1.0s?z?i2

1 0.0

4

-1.0

If additional plant growth does notoccur, forage quantity declines as for-

age is removed. Forage quality also

declines because livestock selectively

graze the highest quality forage first.The rate of decline in forage quantity

and quality during drought is much

more pronounced than in an average

growing season. Even under averagegrowing conditions, animal perform-

ance declines rapidly during the latterpart of the summer grazing season

(Figure 5). This decline is because for-age quality deteriorates as plants ma-ture. During drought, calf gain may beentirely from the back fat of the

cow.

Under any circumstance there willbe a level of remaining forage belowwhich animal performance will de-

\\

YEARLING STEERS

\\\

88

88

GAIN 8

LOSS- - -

88

88

COWS (NURSING CALVES) t\\8

I I I I I IMA Y JUN JUL AUG SEP OCT

Figure 5. Seasonal patterns in average daily gain of different classes of livestock duringthe summer grazing season over a 15 year time period in north central

Colorado (Klipple and Costello 1960).

cline. Minimal levels of remaining

forage on shortgrass prairie dominatedby blue grama in north central Colo-

rado were 350 to 400 lb/acre (Bement

1969). These values are based upon

average daily gains over three stockingrates for 19 years. Given the differ-

ences in plant morphology between

shortgrasses and tallgrasses, minimumlevels of remaining forage for animalperformance on tall grass and sandhills

rangeland in good to excellent condi-

tion appear to be from 600 to 700 lb/ac. End of season remaining forage onthese sites would have a higher ratio of

stem to leaf tissue compared to short-grass sites. It is unlikely that smalleramounts of total remaining herbagewould provide the necessary protection

against wind and water erosion on

sandhills sites.

Excessive stocking rates willreduce animal performance when thequantity and/or quality of forage

available per animal is less than

nutritional requirements for mainte-nance, growth, gestation, and/orlactation. Puberty or sexual maturity in

cattle is correlated with body weightand is relatively independent of age. If

calf growth is reduced by excessivegrazing pressure during the summer,

the onset of puberty in replacementheifers could be delayed.

Nutritional deficiencies also havean adverse effect on conception rates,

especially if cows are thin at calving.

Conception rates will first decline inlactating first-calf heifers. Lactation

increases cow nutrient requirements

substantially. Continued nursing

further delays a cows return to estruswhen nutritional deficiencies occur.

Early weaning of calves may be the

most efficient management practiceavailable for maintaining reproductive

performance when nutritional stress

occurs (Wallace and Foster 1975).Drought may dramatically reduce

the period of time during which green

forage is available to livestock. How-ever, forage that cures at early stages

of plant development is often of higher

than average quality. While mid- and

late-season forage quality may be

higher than normal, the quantity of

forage is reduced. As a consequence,

ranchers who reduce stocking rates to

-7-


12/27

account for reduced quantity of forage

under drought conditions often exper-ience above average animal perform-

ance through the end of September.

Supplementation

Supplements can be fed to correct

nutrient deficiencies and/or to improvethe digestibility of existing forage.Livestock can also be drawn into

underutilized areas with supplements.

This practice can be effective evenwhen contrasting range sites or topo-

graphic differences occur within pas-tures. The economic efficiency of sup-

plements declines as the differencebetween livestock requirements and

forage quality increases. The cost ofsupplements may exceed the potential

return from improved animal perform-

ance. Supplements are generally morevaluable in the first year of drought

because the amount of carryover for-

age declines dramatically as droughtcontinues. There are several critical

issues that must be addressed whenconsidering supplements:

(1) What are the other alterna-tivei?

(2) What type of supplement isneeded?

(3) What effect will it have onanimal performance?

(4) How will the product affectrange or pastureland?

(5) What is the total cost of thesupplementation program?

Supplementation should not beused to maintain livestock in pastures

DECISION RULES FOR DROUGHT STRICKEN RANGELAND

ADEQUATE FORAGE QUANTITY FOR SITE STABILITY

ADEQUATE FORAGE OUANTlTY

FOR ANIMAL PERFORMANCE

MORE THAN

400 LB/AC SHORT GRASS

700 LB/AC TALL GRASS

(NO) 1

+ (YES)BALANCE STOCKING RATE

UTILIZATION

ON KEY SPECIES)

-G-(YES)+- ADEQUATE PROTEIN

I(NO)

USE A PROTEIN SUPPLEMENT

Figure 6. Flow chart demonstrating a sequence of decision making processes for the

management of drought stricken rangeland.

after proper levels of forage have beenremoved (Figure 6). Excessive grazing

and mechanical damage of droughtweakened perennials, even though dor-

mant, will cause long-term delays inrange recovery. Daily feeding of morethan 3 to 4 lb of a grain base supple-ment should be considered as replace-

ment feeding, not supplementation.When replacement feeds are used afterforage supplies have been depleted,

livestock should be placed in pens or

small paddocks to minimize damage torangeland.

Protein and energy are the twomajor nutrients that will most likely be

considered. If the quantity of forage isadequate, but quality is low because of

inadequate protein, supplementationcan be beneficial (Figure 6). The rela-

tive composition of current year and

carryover forage must be consideredwhen making decisions on supple-ments. The average maturity of current

year forage is also a key factor. Imma-ture forages contain about 12 to 15percent crude protein on a dry matterbasis. Plants in the early heading stage

contain about seven to 10 percentcrude protein. Protein content of cured

forages declines as stem/leaf ratiosincrease. Carryover tall and midgrass

forages generally contain less thanfour percent protein. The protein con-

tent of carryover shortgrass and uplandsedge forage may be five to seven

percent.Protein in range and pastureland

supplements should consist of allnatural sources. Non-protein nitrogen

is poorly utilized when fed with low

quality forage. When an adequatequantity of forge is available naturalprotein supplements will improve

forage digestibility, intake, and animalperformance. Proper utilization will

occur sooner and total days of grazingwill be reduced because the rate offorage removal increases (Figure 6).

Even though pastures are grazed forfewer days, the value of the forage foranimal performance can be improved

substantially. Protein supplements can

be fed two or three times weekly with

satisfactory results.

Protein supplements that increase

forage digestibility will also increasethe amount of energy obtained from

-8-


13/27

the diet when adequate quantities offorage are available. While proteinsupplementation may improve theenergy status of the animal, energy

supplementation will not offset aprotein deficiency. If protein levels areinadequate, supplementation with

energy alone will generally reduce

digestibility of forage consumed.Energy in range grasses is rarely

deficient for mature beef cows whendietary protein content is high.

Creep feeding is often consideredwhen forages are in short supply.Under most conditions it is more costeffective to wean early and feed calves

in confinement. For more information

refer to Creep Feeding Beef Calves(G74-166), available through theNebraska Cooperative Extension or

Creep Feeding (GPE 1550) in the

Beef Cattle Handbook available inmost Extension offices.

Early weaning is generally more

economically efficient than supple-mentation of pairs. For example, crudeprotein requirements decline from 10-12 percent for a lactating cow, to

seven percent for a dry cow. Thus, aforage resource that will not support

milk production may be adequate formaintenance of dry cows. Weaning

calves will reduce cow energy require-

ments by about 30 percent and crude

protein requirements by about 50percent (Table 1).

Table 1. Daily nutrient requirements of asuperior milking 1100 lb cow

when dry and when producing 20

pounds of milk each day.

TDN Crude Protein

Dry Cow 9.5 pounds 1.4 pounds

Lactating Cow 14.5 pounds 2.6 pounds

Feeding high levels of properlybalanced protein-energy concentrates

on rangeland can stretch availableforages. However, this practice isgenerally not recommended because of

the following three points:

(1)

(2)

Utilization of concentrates is

often relatively poor on grass-

lands compared to feeding in

confinement,Protein/energy balances of

concentrates can only be

roughly estimated because ofour inability to measure the

quantity and quality of forage

consumed over time from thepasture.

(3) Grazing will continue because

of habit or boredom, regardlessof supplementation. This can

cause serious long-term deter-ioration of rangeland.

Vitamin A deficiencies can occurduring drought. Vitamin A should be

supplemented when cattle do not haveaccess to adequate green forage for 90

days or more. Cattle convert carotenefrom green forages into vitamin A.

When plants cure, carotene contentdeclines rapidly. Cattle store large

amounts of vitamin A in the liver, but

these reserves may be depleted duringdrought. For more information on

feeding beef cattle request a copy ofFeeding the Beef Cow Herd Part II-

Managing the Feeding Program (G80-497) from the Nebraska CooperativeExtension.

Toxicity Associated with Drought

The potential for poisonous plant

problems increases under drought con-ditions. Because less desirable forage isavailable, livestock losses may occur

even where problems have not been ob-

served in preceding years. Some pois-onous plant species are drought tolerant

and produce green foliage under dryconditions. When combined with re-

duced opportunity for selective grazing,the risk of poisonous plant problemsincreases dramatically. Larkspur, Rid-

dell groundsel, death camas and poison-

vetches are examples of native speciesthat occur even on rangeland in good or

excellent condition. The identification

and management recommendations for

common poisonous plants are summa-rized in Nebraska Poisonous Range

Plants (EC85-198), available throughthe Nebraska Cooperative Extension.

Forages high in nitrates are anothernemesis for livestock during drought.

High nitrate accumulations may occurin warm season annual forages or cereal

crops that are used for emergency feed.

Nitrates should be suspected if plant

growth is reduced or stopped because ofdrought. Nitrogen fertilized crops are

most hazardous. Nitrates are inter-

mediate products of protein formation

-9-

in plants. If plant growth is reduced by

drought, protein formation is stoppedand the nitrate concentration increases.After ingestion, nitrate is converted to

nitrite in the rumen. Nitrite interferes

with oxygen transport in the blood.High nitrate intake may cause abor-

tions or death by asphyxiation. Man-

agement recommendations for theevaluation and use of high nitrate for-age are presented in the section onUsing Annual Forages in this hand-

book.

The potential for grass tetanyincreases following drought. Reduc-tions in standing dead plant material

lead to high percentages of lush,current year forage in livestock diets in

the spring. Management recommenda-tions for prevention of grass tetany are

contained in Grass Tetany (G73-32)

in Nebraska and Grass Tetany inCattle (FS586) in South Dakota,available through your local Extension

office. Ranchers should evaluate theirpasture conditions well before turn-out, and if appropriate, start magne-sium supplementation programs to

reduce grass tetany.

Clinical symptoms of grass tetanyand larkspur consumption are similar.

The highest potential hazard period for

both occurs in the spring. It is impor-tant to have a specific diagnosis

because while both affect the centralnervous system and animal coordina-

tion, treatments are different. Animalswith grass tetany often respond to

prescribed treatment but, there is notreatment for larkspur poisoning.

Animals poisoned by larkspur should

be left to recover on their own. Thestress of movement or attempted treat-

ment may cause death in what may

have been a sublethal dose from whichthe animal could have fully recovered

if left alone. If grass tetany symptomsare seen check for the presence of

grazed larkspur plants. If plantpoisoning is confirmed, move all able

livestock to a pasture without larkspurand with adequate grass forage as soon

as possible. If grass tetany is con-

firmed, begin treatment and prevention

immediately.

During drought, water qualityoften declines in stock ponds wheresoil has been deposited by runoff. Salt


14/27

concentrations increase with higherthan average evaporation and reducedwater inflow during drought condi-

tions. Where stock ponds are the only

water source, pastures should be

grazed early in the season before

extensive evaporation. Livestock water

requirements will also be lower when

cool temperatures occur. When waterquality is poor, most livestock reducetheir water intake which reduces

performance. When animals becomethirsty enough, they will eventuallydrink a large quantity of salty water.

These animals may die rapidly (Table

2). This situation may become even

more dangerous if livestock are forced

to eat drought stricken forages with a

high salt content, such as saltgrass or

greasewood.

Table 2. Dangerous levels of salt content in

livestock water.

Livestock

Cattle

Sheep

Total Dissolved

Solids

3,000 ppm

7,000 ppnl

Under certain conditions pond

water may develop lethal concentra-

tions of blue-green algae. Algae multi-

plies rapidly under hot and dryweather conditions. Winds accumulatethe algae along downwind shorelines

on the surface of water. Under drought

conditions water quality can changefrom non-toxic to toxic in several

hours. Livestock that drink can die

before traveling a few hundred yards

or may suffer for a day before death.Animals that recover may slough

white hide. Determining the cause of

death is difficult because changes in

weather can eliminate the problem andpositive identification of blue-green

algae requires microscopic examina-tion.

PREDICTING FORAGE PRODUCTION AND

STOCKING RATES

Weather variables and soil mois-

ture content can be used to estimate

forage production in the coming grow-

ing season. The level of predictability

is influenced by soil texture and there-fore differs among range sites. Regard-less of site, the length and severity ofpast drought must be considered. The

following methods are based uponvegetation not impaired by long-term

drought. If drought has reduced peren-

nial plant cover, grass yields will be

over-estimated with these methods.

Sandy Soils-Spring Decisions

Methods of predicting forage pro-duction on sandhills rangeland in good

condition, on Valentine soils, were

examined by Dahl(l963) in northeast

Colorado. The soils and vegetation in

the study area are similar to sandhills

rangeland in Nebraska and South

Dakota. The depth of moist soil onApril 15 was highly correlated withforage production from May 1 toAugust 7, the primary growing season.There is usually a distinct color change

between moist and dry soil on sand-hills range sites. Conventional post

hole diggers or soil augers can be used

to randomly sample depth of moist soil

in pastures. The relationship of prob-

able stocking rate and depth of moistsoil in April is presented in Figure 7.

Since the initiation of the growing sea-son is delayed northward from Colo-rado, depth of moist soil could be

120 -

100 -

80 -

6

40

- LEAVE HALF OF YIELD* * * L E A V E 700 LBS OF YIELD

******

l

I I I I I I I I I I I I6 12 18 24 39 36 42 46 64 60 66 72

INCHES OF MOIST SOIL APRIL 15-30

The relationship of depth of moist sand in mid- to late-April and probablestocking rates for sandy and sands range sites in good to excellent range

condition in western Nebraska and western South Dakota. Rangeland in fair

or poor condition may not produce enough forage to sustain these predicted

stocking rates. Drought and/or overgrazing in preceding yearswill reduce thecarrying capacity of rangeland (modified from Dahl 1963).

-lO-


15/27

checked as late as April 30 in SouthDakota and northern Nebraska.

Because of the decline in herbageproduction under drought conditions, it

may be necessary to reduce stockingrates the following year, regardless ofmoisture conditions, to leave enough

cover for site protection. Locate the

average depth of moist soil observedin your pastures in Figure 7, move upto the bottom stocking rate line and

then to the left hand scale to determine

the stocking rate necessary to leaveadequate plant cover on unstable sand-hill pastures. If plant growth and sur-

vival were dramatically reduced by

preceding drought and wind erosionhas increased, it may be necessary torest pastures or to defer grazing untilfall or early winter. Ifsandhill pastures

are stable, move up to the top stocking

rate line and left to the stocking ratescale.

Loamy Soils-Spring Decisions

Forage production on loam togravel loam soils near Cheyenne,

Wyoming was highly correlated withtotal precipitation from March throughMay (Hart 1987). Spring precipitationaccounted for 94 percent of the annualvariation in forage production. Needle-

andthread, western wheatgrass, and

blue grama dominate the sites wherethis study was conducted. These siteswould be similar to silty and limyupland range sites in western Nebraska

and South Dakota. The relationship ofprobable stocking rates and total pre-

cipitation from March through May is

presented in Figure 8.

Clayey Upland-Spring Decisions

The most reliable model for pre-dicting yield on clay uplands in Kan-sas was based upon total precipitation

in May and June during the currentgrowing season (Hulett and Tomanek1969). The sites in this study weredominated by blue grama and buffalo-

grass in association with mid-grass

species. This method does not provide

as much lead time nor was it as accur-

ate as the procedures described for

sand and loam soils. Warm season

shortgrasses often respond to precipita-

120

100

80

60

The relationship between total precipitation from March through May andprobable stocking rates on silty and limy upland range sites in western

Nebraska and western South Dakota (modified from Hart 1987).

II I I I I4 6 8 10 12 14

MARCH-MAY PRECIPITATION (IN)

tion in July and August. Even so, lowprecipitation in April and May on

clayey range sites does provide an

indication of pending shortages inforage resources.

ClayeylLoamy Upland-Fall Decisions

Some range livestock producers

have used a flexible stocking ratebased upon total precipitation from

October through September during the

preceding two years (Ralph Cole Per-sonal Communication). Precipitation

from the preceding two years has a

direct influence on forage production

and range recovery in the upcomingyear. Greatest emphasis is placed on

precipitation in the year just past be-

cause it has the greatest influence onvegetation in the upcoming year. The

-ll-

flexible stocking method provides an

opportunity to capitalize on vegetationsurpluses during favorable years, and

enhance vegetation recovery after

drought. This method also provides anopportunity to reduce livestock num-bers before wintering costs are in-

curred. This prediction assumes thatprecipitation in the upcoming winter

and spring will be near average. If theydiffer dramatically from average

stocking rates will need to be adjustedfurther.

The following example of calcu-

lating flexible stocking rates is pre-

sented for a ranch with a long-termaverage stocking of 2700 AUMs for

its rangeland forage base. Precipitation

in the year just past is weighted at 75percent while precipitation from two

years ago is weighted at 25 percent.


16/27

Precipitation Records

Long-term average precipitation = 16 inches1985 forage year (Oct 84-Sep 85) precipitation = 12 inches1986 forage year (Oct 85Sep 86) precipitation = 22 inches1987 forage year (Oct86-Sep 87) precipitation = 18 inches1988 forage year (Oct 87-Sep 88) precipitation = 12 inches

1989 forage year (Oct 88-Sep 89) precipitation = 8 inches

Stocking for an Average Grazing Year = 2700 AUMs

PREDICTIONS

Stocking for 1987 Grazing Year:

RATIONALE

(1985)

(1986)

12 in x .25 = 322 in x .75 = 16.53 + 16.5 = 19.5

19.5/16 x 100 = 121.9 percent

121.9 percent x 2700 = 3291 AUMs

Increased stocking takes

advantage of good foragecarryover and improved

plant vigor from 1986.


(1986) 22 in x .25 = 5.5 Predicts good vigor and(1987) 18 in x .75 = 13.5 likely high production

5.5 + 13.5 = 19.0 as a result of above

19.0/16 x 100 = 118.75 percent average precipitation

118.75 percent x 2700 = 3206 AUMs in 1986 and 1987.


(1987) 18 in x .25 = 4.5 Anticipates decreased

(1988) 12 in x .75 = 9.0 carryover and plant

4.5 + 9.0 = 13.5 vigor resulting from a13.5/16 x 100 = 84.4 percent relatively dry year in

84.4 percent x 2700 = 2278 AUMs 1988.


(1988) 12 in x .25 = 3 Stocking is greatly reduced

(1989) 8 in x .75 = 6 after two dry years in

3+6=9 anticipation of diminished9/16 x 100 = 56.25 percent forage supply and to allow

56.25 percent x 2700 = 1519 AUMs for range recovery.

Cool Season Pastures-Spring

Decisionsgrazing, 40 inches of moist soil onApril 15 would show a high probabil-

The depth of moist soil in the

spring is a good predictor of probable

forage production on tame wheatgrassand bromegrass pastures. If good

stands exist and root systems have not

been reduced by drought and/or over-

ity that average stocking rates can besustained. Limited production will

occur with less than 20 inches of moist

soil. Maximum forage production will

occur with 60 inches of moist soil

(Johnson 1988).

Yield After Prolonged Soil Moisture

Shortages

Soil and air temperatures influ-

ence plant ability to produce foragewhen adequate soil moisture occurs.Optimum temperatures for rapid plant

growth generally occur for only 2 to 4

weeks. If moisture stress inhibits plantdevelopment, the remaining amount oftime during which plants can grow

rapidly is reduced because air tem-peratures either become too high or

too low for optimum plant growth.Plants grow rapidly near the mid-

point of their growing season when

optimum temperatures and adequate

soil moisture occur. If a prolongedshortage in soil moisture limits plant

growth beyond the mid-point of the

primary growing season, forage

production will often be less than halfof average yield, even with the adventof adequate soil moisture, unless

unseasonable temperatures occur.Primary growing seasons for dif-

ferent forage species differ across ourregion. Precipitation and the length of

the frost free period increase from

west to east in Nebraska and SouthDakota. Average annual precipitationranges from 12 to more than 30 inches.

The average frost free period rangesfrom 135 to 210 days. Opportunities to

use alternative forage resourcesincrease as the frost free period

increases.Drought stress early in the grow-

ing season may reduce the number ofshoots that develop in perennial grass-

es and some annual forages. The ap-

proximate time at which prolongedsoil moisture shortages will cause sig-nificant reductions in yield are pre-

sented for different forage resources in12-16 and 20-24 inch precipitation

zones in Figure 9.

Using Annual Forages

Where suitable cropland exists,

annual forages can be used to reduce

grazing pressure or to provide periods

of critical deferment for range and pas-

tureland. Annual crops can also be

used for hay production to offset

drought induced shortages in feed. Ifannuals are not grazed or cut for hay,

-12-


17/27

PROBABLE REDUCTIONS IN FORAGE PRODUCTION

WITH PROLONGED SOIL MOISTURE DEFICITS

12-16 Precipitation Zone 20-24 Precipitation Zone

Winter Cereals

June

Summer Annuals+-ILate Planted I

Summer Annuals

Winter Cereals

Wheatgrass Pastures

Spring Cereals

Bromegrass Pastures

Cool Season Native

Switchgrass

Warm Season Native

Big Bluestem

Indiangrass

Summer Annuals

Late Planted

Summer Annuals

Winter Cereals

For Fall Grazing

Fall Green-Up

Native & Tame

Fall Green-Up

Native & Tame ,-J August

Figure 9. Approximate date after which prolonged soil water deficits will cause measurable reduction in yield of different forage

resources in 12-16 and 20-24 inch precipitation zones. Timing of the critical periods in the 16-20 inch precipitation zone willfall between the above dates.

most can be harvested for grain. Thebenefits of annual forages cannot befully realized without advanced

planning. Delay in seed purchases and

seedbed preparation will reduce the

number of crop alternatives (Table 3).

Forage yield and quality depend upon

seeding date, rate and method.Efficient selection and use of annualforages will depend upon land,

equipment, and labor resources.There are three categories of

annual forage grasses based uponseason of growth and probable date at

which grazing could begin (Table 4):

(1) winter cereals, (2) spring cereals,and (3) summer annual forage grasses.

Winter cereals such as triticale and

standard height wheat can be used toproduce early spring forage and delay

turnout on range or pastureland.Winter triticale is more aggressive

than winter wheat and less prone toweed infestations. Spring cereals such

as late maturing oats can also be used

as a spring forage 15 to 30 days afterwinter cereals.

Summer annual forage grasses canbe used as a mid-summer, late summer

or fall grazing resource. Under irriga-

-13-


18/27

Table 3. Cultural practices for annual forage grasses.

TYPE:

Winter Cereals

Standard height

winter wheat,

winter triticale

Spring Cereals

Late maturing

oats

Summer Annuals

Forage sorghum, sudan-grass, sorghum x sudan-

grass crosses and millets.

SEEDING Early fallDATE: September l-20 Early springMarch 15 -

April 15

Two weeks after corn, up to

mid-July. Sudangrass, for-

age sorghum and sorghum

x sudangrasss crosses: soil

temp. above 60 F.Millets: Soil temp. 6570F.

SEEDING

RATES:

1.2-l 5 bu/ac 2 bu/ac Sudangrass, sorghum xsudangrass crosses and

foxtail millet: 15-20 lb/ac.

Forage sorghum and pear1

millet: 6-12 lb/ac.

FERTILIZER:

Nitrogen and phosphorous are primary nutrient concerns. Fertilizer should be

applied according to soil tests. Excessive application of nitrogen will increase the

potential for high nitrate content in forages. Adequate phosphorus is essential for

root development.

%elect types and varieties within types that are adapted to the local environment. Assistance is availablethrough the local Extension Office.

Table 4. Grazing management recommendations for annual forage grasses.

EARLIEST

PROBABLE

GRAZING

DATE:

Winter Cereals Spring Cereals Summer Annuals

April 1-15 May 1-15 July 1-15

GRAZING Begin at 6-8

MANAGEMENT: in. (5 leaf)

but no later

than boot.

Graze contin-

uously or 2-3

pasture

rotation.Graze to 2 in.,

defer 2 weeks.

Grazeable in

30 days. Begin

at 6-8 in. (5

leaf) but no

later than

boot. Graze

continuously.

Provides 6-8weeks grazing

season.

Grazeable in 40-45 days.

Begin at 15-20 in.

(sudangrass and pearl

millet), 18-24 in.

(sorghum and sorghum

x sudangrass crosses).

Use two or more pastures

with staggered planting

dates. Graze rapidly to

6 in. Defer 3 weeks.

PROBABLE

STOCKING

RATE:

1.5-3.0 AUM/ac 1 .O-2.5 AUM/ac(Not fallowed) (Not fallowed)

2.5-3.5 AUM/ac 1.5-3.5 AUM/ac

(Fallowed) (Fallowed)

1.5-3.5 AUM/ac

1st grazing cycle.Possibility of

regrowth

tion or with timely precipitation someof these forages may be used in hayingand grazing combinations during the

same year. Species and varieties in this

category differ considerably in height,stem diameter, length of growingseason, forage production potential,

regrowth, and content of antiquality or

toxic compounds. There are five typesof summer annual forage grasses:forage sorghum, sudangrass, sorghum

x sudangrass crosses, pearl millet, and

foxtail millet.Young plants and young leaves in

sorghum, sudangrass and sorghum xsudangrass hybrids contain a chemical

that breaks down and is released asprussic acid. Use varieties in thesethree types that have been selected forlow prussic acid content such as Pipersudangrass. Danger of prussic acidpoisoning is low when sorghum,sudangrass or sorghum x sudangrass

crosses are not grazed until plants are18 to 24 inches tall. Prussic acidconcentrations increase when plantsare stressed by frost or drought.Prussic acid breaks down rapidly in

dead plant tissue. If new tillering doesnot occur and plants are 18 to 24inches tall, grazing can begin 5 daysafter plants have died. Forage and hayshould be analyzed for prussic acid

content when uncertainty occurs.Millets do not contain prussicacid. Foxtail millet matures early and

has limited regrowth potential . It ispoorly rooted and may be pulled upduring grazing. It is best suited for

haying or single periods of intensive

grazing. Foxtail hay is excellent forcattle and sheep but not recommendedfor horses. Pearl millet is well rooted

and has good regrowth potential. Itmay be grazed when plants are 15 to20 inches tall. Specific information for

localized conditions can be obtainedthrough your local Extension office.

For more information, request a copy

of Summer Annual Forage Grasses(G74-171) in Nebraska or SmallGrains for Forage (FS662) in South

Dakota.

Nitrate accumulation can occur in

any annual forage crop if growing

conditions are droughty. Excessive

nitrates are more likely to occur onsites that were fallowed or heavily fer-

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19/27

tilized with nitrogen in the currentand/or preceding year. Nitrates tend toconcentrate in stem bases, but they aregenerally not a problem unless live-

stock consume the lower one-third ofplants. Content of nitrates in hay canbe reduced by raising the cutting

height. Nitrate concentrations can also

be reduced by ensiling the crop. When

in doubt, send a representative forageor feed sample to a laboratory foranalysis. Contact your local Extensionoffice for more information on ni-

trates. In Nebraska refer to NebGuideG74-170, Nitrates in Livestock Feed-

ing and in South Dakota refer toExtension Bulletin FS420 Forage

Nitrate Poisoning.

DROUGHT MANAGEMENT PLANS

A drought plan should minimizefinancial hardships and hasten vegeta-tion recovery after drought. Droughtplans identify action to be taken at the

first sign of drought as well as with

continued indications of pending for-age shortages. Plans for stocking rate

adjustments need to be specific interms of method and date. The timing

of actions should be based upon sea-sonal check points. Critical evaluationdates at which livestock requirements

are balanced with available forage andfeed resources are:

April 15-30:. Determine average depth of

moist soil on sandy, sands and

choppy sands range sites andestimate probable stockingrates.

. Assess growth of introducedcool season pastures.

. Evaluate stand quality andprobable forage production of

winter and spring cereals.

May l-30:. Estimate probable stocking

rates on silty and limy upland

rangeland, based upon March

through May precipitation.. Determine if yield of native

cool season species on range-land is above or below

average.. Monitor green-up of native

warm season species onrangeland. Alternate forages,

stocking rate reductions and/or modifications of grazing

strategies may be needed if

there is a delay in green-up.

June l-30:. Assess establishment and

stand quality of summer an-nual forages and soil moisture

conditions.

July l-30:. Determine if yield of native

warm season species on

rangeland is above or belowaverage.

. Assess establishment andstand quality of late plantedsummer annual forages andsoil moisture conditions.

August l-30:. Estimate or measure yield of

summer annuals harvested for

feed or grown for late season

grazing.

September l-30:Inventory current year, carry-

over, and purchased hayresources.

Make a final assessment of

yield of annual forages grown

for late season grazing.

Inventory other harvested

feed and determine the quan-tity of crop residue on crop-

land.

Estimate amount of forage inwinter pastures.

October l-30:. Use October through Septem-

ber precipitation to predict

stocking rates for the next

summer on clayey/loamyrange sites.

When a production year has beencompleted under short- or long-termdrought, identify and address the

weakest components of the manage-ment plan that have the greatest effect

on production costs. Modify plans foradjusting livestock numbers or forage

and feed resources for next year or for

the next drought. For more informa-tion on estimating forage supplies andbalancing livestock requirements with

forage and feed resources refer to A

Guide For Planning and Analyzing Ayear-Round Forage Program (EC 86-1 13) available from Nebraska Coop-

erative Extension.

The color green can have pro-found psychological effects on rangelivestock producers. Even a smallamount of spring or fall green-up can

cause a false sense of security and the

delay of prudent management deci-sions outlined in drought plans.

Pastures with an abundance of

rhizomatous grasses can also look likea dream come true following adrought. Even though perennial grass-

es often produce many seed stalks the

year after drought, total quantity offorage is still well below average. Thisis one of natures cruel deceptions.Loss of plants during drought reduces

plant competition. When adequate soilmoisture occurs, the remaining plantsgrow to above average height because

of reduced competition for nutrients

and moisture. Grasslands cannot re-

cover fully and cannot sustain pre-drought stocking rates in the first year

after drought.A plan of action should be

developed for best and worst casescenarios. If drought breaks early thefollowing year a gradual restocking

plan may be appropriate. Premature,aggressive restocking can cause

serious economic loss because of long-term reductions in the rate ofvegeta-

tion recovery. If vegetation recovery isslow or restricted by continueddrought, a destocking plan will beneeded. Normally, stocking rates in

the year that drought breaks should not

be increased above levels in the last

year of the drought. If animal perform-

ance or remaining herbage were

unacceptable during the preceding

drought year, stocking rates may need


20/27

to be reduced by l0-30 percent in the

following year. Important considera-tions for drought management plans

are outlined below:

(1)

(2)

(3)

(4)

(5)

(6)

Resist the temptation to

restock to former levels inthe year following drought.

As much as possible, next

years forage productionshould be devoted to restoring

protective plant litter andimproving plant vigor.

Plan to delay the initiationof the summer grazingseason by 1 to 2 weeks to

enhance plant recovery.

This delay may result in a 10to 20 percent increase inforage production during the

growing season.

Use rangeland resources

efficiently. Critically evalu-ate distribution of livestock

grazing in all pastures. Usethe least expensive methodsavailable to increase use oflightly grazed areas and re-

duce use in over grazed areas.Distribution of grazing may

be improved by changingtime or season of use or by

strategic short-term place-

ment of salt or mineral. Toolsused to improve distribution

are discussed in Proper Live-stock Grazing Distribution

(G80-504), available throughNebraska Cooperative Exten-

sion.

Determine the availability of

alternative or reserve for-

ages. These could be used to

reduce grazing pressure onrangeland.

Reserve 10 to 20 percent ofyour forage resources incase vegetation recovery

falls short of expectations.

Calculate stocking rates foreach pasture. Use animalunit (AU) equivalents that are

representative measures of

animal weight and/or forage

requirements. Keep and useaccurate grazing records for

each pasture.

(7) Make and implement deci-

sions early to avoid crises.

Delays often lead to intensifi-

cation of the problem, econo-

mic loss, and long-term dam-age to the forage resource.

Questionable Practices

Some management and improve-

ment alternatives are questionableunder drought conditions. Higher than

normal risk is associated with the startof intensive rotational grazing, instal-lation of cross fences and water devel-opments and initiation of weed con-

trol, pasture renovation and fertiliza-

tion projects.

Even with adequate preparation,

errors in intensive rotational grazing

management will occur during im-

plementation. Conservative stockingrates and experience are needed to fine

tune intensive management practices.The number of management decisionsincreases as the number of pasturesand number of grazing periods per

pasture increase. Consequently, the

potential for error also increases.Limited investment in water

development and cross fencing on a

priority basis may be warranted.

Possible examples include:

(1)

(2)

Provision of livestock water

for the use of significant for-age resources that would oth-

erwise be unusable without

water development.Separation of range sites or

seeded pastures that are

capable of producing meas-

urably more forage withimproved control over timeand/or stocking density. This

may involve separating coolseason seeded pasture fromrangeland or cross fencing

subirrigated meadows.

Opportunities to recover invest-

ments for range or pasture improve-

ments often decline dramatically under

drought. The probability of success in

weed control, reseeding, and fertiliza-

tion on dryland sites declines drasti-

cally during drought.

Without adequate soil moisture,

plants cannot use fertilizer efficiently.

Forage yield of smooth brome on asilty clay loam soil in Lincoln, Ne-

braska was studied for eight years(Colville et al. 1963). Excellent standswere established and evaluated with-out irrigation. Precipitation ranged

from 6.5 to 20.5 inches from Decem-ber 1 to June 20, the time of harvest.

Conclusions from this and otherstudies of nitrogen fertilization on

dryland brome pastures in eastern

Nebraska and South Dakota aresummarized below:

(1)

(2 )

(3)

(4)

(5)

The increase in yield from

each pound of fertilizer de-

clines as the total applicationincreases.

As application rates increase,

the amount of precipitation

required to recover totalfertilizer costs also increases

(Table 5).

Nitrogen should not be

applied to dryland pastures inany location under severedrought conditions.

Under moderate drought con-ditions, application of nitro-gen fertilizer should not ex-

ceed 50 to 80 lb/ac in eastern

Nebraska or eastern South

Dakota.

Recovery of fertilizer costsfor up to 80 lb N/ac in eastern

areas of Nebraska or South

Dakota will require 9 to 10inches of precipitation from

December 1 to June 20

(Table 5).

In the western parts of both statestame dryland pastures will not respond

to nitrogen fertilization unless winter

through spring precipitation is averageor above. Nitrogen fertilizer should not

be applied to tame pastures in this

region unless depth of moist soil ex-

ceeds 20 inches by April 1 to April 15.

Application rates should be 35 to 45

lb/ac for wheatgrass pastures. Only the

best stands on the best soils should be

fertilized.

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21/27

Table 5. The influence of total precipitation from December 1 to June 20 on addi-tional smooth brome forage production from 40, 80, or 120 lb/ac of nitrogen

fertilizer compared to unfertilized yield at the first cut (Colville et al. 1963).

Precipitation Unfertilized

Dec I-June 10 Yield

Additional Forage

Yield Compared to

Unfertilized

40 80120

____________(lb/ac)____________

7 350 310400 610

8 DROUGHTY 350 400 650 880

9 470 460 7801170- - - - - - - - - - - - - - - - - - - - - - - - - -

10 940 6901120 1380

11 AVERAGE 1750 94 0 1430 2270

12 2350 1650 2460 3860-----------_-_-----------_13

ABOVE2470 2040 3400 4150

AVERAGE14 2303 3890 4470

RANGELAND RESOURCE INVENTORY

Ranchers who know the current

capability and condition of theirresources can make more efficient

drought management plans than thosewithout a resource inventory. Grazingrecords also provide valuable insight

into the present condition of forage re-

sources.

Pasture evaluations should be

made within a 1 or 2 day period, well

in advance of each grazing season.

Plant vigor, range condition and theamount of remaining forage should beestimated in each pasture. Plant vigor

is indicated by the relative size ofplants and the height and frequency ofseed stalks. Range condition is directlyrelated to the amount and diversity of

desirable grass species. The remaining

forage has a direct influence on site

stability and also provides an indica-

tion of how well root systems grew in

the preceding year. Assistance in range

evaluation is available through localSoil Conservation Service offices.

The relative contribution of cool

and warm season grasses to the totalamount of forage produced on theranch is a major factor in drought man-

agement strategies. The percentage offorage produced by cool and warm

season grasses should be estimated in

each pasture. Plans for pasture use can

then be modified to capitalize on pre-

cipitation that favors either cool or

warm season grasses. Cool season

grasses grow primarily from late Aprilto early June. Warm season grassesgrow primarily from early June

through July. If adequate soil moistureis not available by the midpoint of a

species primary growing season, sub-stantial reductions in forage produc-

tion will occur (Figure 9). Information

on the identification and season of

growth of grasses is contained in

Nebraska Range and Pasture Grasses

(EC85-170), available through Nebras-

ka Cooperative Extension.

Rank pastures into high, moder-

-17-

ate, and low categories based upontheir current ability to produce forage.

Forage production potential dependsupon site characteristics as well as

range condition and plant vigor. Poten-tial production of different sites is dis-

cussed in the following NebraskaExtension publications Nebraska

Range Judging Handbook (EC 84-109) and A Guide For Planning and

Analyzing A Year-Round ForageBalance Program (EC 86- 113). The

Soil Conservation Service has devel-

oped comprehensive summaries ofrange site forage production potentials.

High-ranked pastures need to bemanaged for optimal yield duringdrought. Moderate-ranked pastureswill produce more forage than lowranked pastures and provide flexibility

in the development of grazing strate-

gies. Moderate-ranked pastures can beused for early or mid-season grazing toprovide an extended period of uninter-rupted plant growth for optimal forageproduction in high ranked pastures.

Conduct a careful review of low-ranked pastures. First, identify the

low-ranked pastures composed of

range sites that are capable of produc-ing abundant forage. Determine if the

low rank of these pastures is a result of

recent abuse, drought, or long-termabuse. If the pasture is ranked low

because of one year of overgrazing ordrought, it is possible that plants willbe able to recover rapidly. If the

forage from these pastures makes up asmall percentage of the total forage

base, these pastures should be deferred

until after key grass species haveheaded to optimize recovery rate.

Some pastures may be ranked low

because they are range sites incapable

of producing abundant forage or theyhave a long history of abuse. The re-covery of these pastures is not a part of

your drought recovery plan, but in-stead is a part of a long-term, ranch-wide range improvement program. Re-covery of these pastures may need to

be delayed until better pastures can be

returned to near optimal production.

These low ranked pastures may be

grazed when providing deferment to

higher priority pastures. Increases in

forage production that occur in moder-ate and high ranked pastures will pro-


22/27

vide the best opportunity for futuredeferment and recovery of long-termabused pastures. An adequate level ofprotective cover must still be main-

tained when grazing low ranked pas-

tures.

Use grazing records to calculate

the stocking rate for each pasture dur-

ing the previous year(s). Determine ifstocking rates or time of grazing have

influenced the rank of pastures. Deter-

mine what stocking rate and time ofgrazing combinations were least andmost detrimental during preceding

years. If good grazing records are not

available, now is the time to begin.Record the class and number of live-

stock, and all dates of entry and re-moval for all livestock for each pas-

ture. Long-term pasture records areessential for making intelligent grazingmanagement decisions.

GRAZING MANAGEMENT

Drought management should

capitalize on all forage resources andminimize overgrazing. Conservativestocking rates and frequent pasture ob-servations are necessary to minimizeovergrazing regardless of grazing

strategy. Livestock distribution andtime of grazing determine how well

forage resources are used. Techniquesand management options are discussed

in Proper Livestock Grazing Distribu-tion (G80-504) available throughNebraska Cooperative Extension.

Rotational grazing can be used tocontrol grazing time. Livestock are

concentrated into one or a limitednumber of pastures. The time at whichpastures are used or deferred under

rotational grazing should be basedupon a resource inventory and man-

agement objectives for each pasture.

Livestock water supply must be

carefully assessed before implement-ing rotational grazing. Daily consump-

tion and evaporation may total 20 to

25 gal. per cow-calf pair during July

and August.

The benefits of rotational grazing

are accrued when used during theyears before drought. Proper stocking

in conjunction with rotation grazingwill improve plant vigor and range

condition. These improvements will

moderate the effect of drought. Ranch-

ers must balance practices designed for

o

animal response to drought: drought management on range and pastureland

Documents