NUTRITIONAL VALUE OF they mature. Nitrogen is …...Range Cattle Nutrition 1993 1 they mature....

Range Cattle Nutrition 1993 1

they mature. Nitrogen is moved by thegrass plant from above-ground partsavailable to the grazing animal tostorage organs below the ground asthe current years grass growth ma-tures. Shrubs, on the other hand, aregood sources of protein even after theyreach full maturity because nutrientsremain in branches and leaves as wellas below ground. Forbs, in general,are intermediate between shrubs andgrasses with respect to protein contentduring most seasons.

Phosphorus, a macro-mineral, is oftenlimiting in range forage plants.Grasses are low in phosphorus soonafter they form seed. Shrubs aregenerally considered good sources ofphosphorus for general animal mainte-nance and gestation, even whenmature. Most forbs have a phosphoruscontent only slightly lower than that ofshrubs. Phosphorus content of plantscan fluctuate depending on the soilstatus. Soils high in phosphorus willallow plants to contain more phospho-rus than where soils are limiting inphosphorus content.

Energy values of forage are commonlyreported as Total Digestible Nutrients(TDN) or Digestible Energy (DE).Grasses are generally considered goodsources of energy primarily because oftheir high content of cellulose. In veryrank grasses however, digestibility willbe so low as to reduce intake andthereby reduce total energy intake.Digestibility is the proportion of adietary nutrient available for animalmetabolism and indirectly tells ussomething about intake (as digestibilitygoes down, intake may go down).Shrubs are not considered goodsources of energy after they reach fruitdevelopment. Again, forbs are inter-mediate between grasses and shrubsin furnishing energy. In my opinion,energy is more frequently a limitingfactor to livestock production on

NUTRITIONAL VALUE OFRANGE FORAGE FOR

LIVESTOCK

George Ruyle 1

Grazing is the base of the nutritionalprogram for range cow outfits. Onsome ranches, range forage is the onlyfeed source cattle have except for saltand water. During periods of initialplant growth in the spring and summerall forage species are high in nutrientcontent although moisture content mayalso be high and limit dry matter intake.However, as plant growth stagesadvance, the nutritional differencesamong forages becomes more evident,especially during the fall and winterperiods.

The nutrient value of range forages isbest tested by their ability to provide forthe nutritional requirements of thegrazing animal during the variousseasons of production. Plant nutritionalvalues should be compared with thecorresponding animal requirementsduring the year.

The nutrient evaluation of range foragecan be based on how much protein,phosphorus and energy the plantscontain. These, along with carotene(vitamin A) are the four principlenutrients that may be limiting onrangelands. These can best be dis-cussed by dividing the plants into threecommon forage classes, grasses, forbs(broad-leaved, herbaceous plants,often called weeds), and shrubs.

Protein is calculated from the amount ofnitrogen contained in plants. Grassesdecline in digestible protein rapidly as


reserves are a necessary part ofranch planning, and some amount ofplant material should be left forresource protection, if pastures areallowed to accumulate a lot of oldplant growth animal production maysuffer. This can be offset by adjust-ments in stocking rates or changes inrange condition. Carefully plannedgrazing can help increase diet quality.In grazing cells for example, thelonger animals stay in a particularpaddock the further diet quality isreduced. If grazing periods areshortened, be sure to consider theimplications of the subsequentlyshorter rest periods.

Supplementation will probably benecessary to achieve high levels oflivestock performance from range-lands although economic analysisshould consider the bottom linebefore any decision on supplementingcattle diets is made. Even thoughtotal production may be reduced,profits may be maximized at lowerinput and offtake levels. Whendetermining whether or not to supple-ment, cow as well as forage condi-tions should be considered, butremember, it is the nutrients providedby the range forage that are supple-mented. Over-supplementation,especially of protein, or supplement-ing too late in the season to improveproduction are not uncommonpractices.

rangelands than is crude protein. Thesingle biggest problem however, espe-cially when forage plants are mature, isgetting enough total nutrients into theanimal each day.

Other factors may also affect the nutritivevalue of range plants. Range condition,for example, may alter total forage intakeof grazing cattle. Research shows thatprotein and phosphorus are about thesame in plants growing on good versuspoor condition range. However, plantspecies on poor condition range may beless digestible than plant species ongood condition range which can reducetotal forage intake by livestock. Theanimals either can’t or won’t eat enough.An appropriate mix of grasses, shrubs,and forbs, is necessary to providenutritious forage to livestock on a year-long basis.

Management factors such as stocking rateand specialized grazing systems canalso influence grazing animal nutrition.Heavy stocking reduces individual animalperformance and can result in damage tothe forage resource. Although theinfluence of animal numbers can bealtered by controlling the time the plantsare exposed to grazing and allowing foradequate recovery periods, properstocking rates are essential to long-termrange livestock production levels.

Grazing systems may reduce or improveforage nutritive value. Although forage

Range Management Specialist 1

School of Renewable Natural ResourcesCollege of AgricultureThe University of ArizonaTucson, Arizona 85721


FROM:

Arizona Ranchers' Management GuideRussell Gum, George Ruyle, and Richard Rice, Editors.Arizona Cooperative Extension

Disclaimer

Neither the issuing individual, originating unit, Arizona Cooperative Extension, nor the Arizona Board ofRegents warrant or guarantee the use or results of this publication issued by Arizona CooperativeExtension and its cooperating Departments and Offices.

Any products, services, or organizations that are mentioned, shown, or indirectly implied in thispublication do not imply endorsement by The University of Arizona.

Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation withthe U.S. Department of Agriculture, James Christenson, Director, Cooperative Extension, College ofAgriculture, The University of Arizona.

The University of Arizona College of Agriculture is an Equal Opportunity employer authorized to provideresearch, educational information and other services only to individuals and institutions that functionwithout regard to sex, race, religion, color, national origin, age, Vietnam Era Veteran’s status, orhandicapping conditions.



INTRODUCTION

Many of the important decisionsranchers make involve the manage-ment of the nutritive intake of theircows. Decisions such as levels andtiming of supplemental feeding directlyimpact the level of nutritive intake ofcows. Decisions such as choice ofbreeding date indirectly impact thelevel of nutrition by changing the timingbetween the periods of the preg-nancy—calving cycle with high nutritiveneeds and periods of forage availability.This linkage between ranchers deci-sions and the nutritive intake of rangecows is complex and involves manyfactors. Further, the linkage betweenthe nutritive intake of range cows andtheir production is also complex. Thiscomplexity makes the analysis ofdecisions impacting nutritive intake ofcows a very difficult task.

In order to provide ranchers a tool toanalyze decisions which impact rangecow nutritive intake, a computer simula-tion of the range cow nutrition—production process has been devel-oped. This program allows ranchers topredict the results of alternative strate-gies of managing the nutritional intakeof their cows and evaluates the resultsin economic terms.

The purpose of the range cow nutri-tion—production simulation is to predictthe results of rancher decisions givenan observed or predicted diet of therange cow. The simulation tracks the

RANGE COW NUTRITION

MANAGEMENT

EVALUATOR

Russell Gum,1 George Ruyle,2

Richard Rice,3 andEric Schwennesen 4

input to the cow and calf on a dailybasis, and predicts their weight dailyand predicts the calving rate for thecows. The simulation is run for aperiod of seven years and a summarymeasure of the present value of thecows production over the seven yearperiod is produced to be used as ayardstick to economically comparedifferent alternatives or conditions.

To use the evaluator, information on thediets of the cows and the nutritivecontent of the forage they are eating isnecessary. The diet data is obtainedby microscopic analysis of fecalsamples to identify undigested plantcells. The nutrition data is obtainedfrom laboratory analysis of foragesamples. Since both diets and thenutritive value of the forage change asthe seasons change these analysesmust be repeated on a monthly basis.For ranches which have not developedthis information the program can still beused by inputting data from nearbyranches or even from ranches in otherareas with similar conditions.

Once the diet and forage data arecollected and entered into the computer,information on the beginning conditionof the cow and on the current manage-ment practices, such as breeding datesand supplementation, must be inputinto the computer. The computer thenpredicts the performance of the cow fora period of seven years and produces aseries of graphs, which are useful inanalyzing the results and formulatingalternative strategies for the computerto evaluate.

The following is an example of how arancher might use the program. Firstthe rancher, working with technical helpfrom an extension agent, would de-velop an estimate of the composition ofthe diet and the nutritional compositionof the forage species in the diet. Anexample of such information in agraphical form is displayed in Figure 1.The line labelled “1” is the percent of


the cow’s intake made up of this particu-lar plant species over a completeseason. The line labelled “2” is anestimate of the percent phosphoruscontained in this particular forage overthe season while the lines labelled “3”and “4” are estimates of the protein andTDN percentages. As can be seen inthe example, both the percentage ofthe diet and the nutritional value of theforage vary greatly over the season.

Next the rancher would specify theparticular management scheme to beused for the base run. For our ex-ample, this is a breeding date of May15th, an initial weight of 900 pounds fora bred cow, a weaning date of October15th, and no supplement. The model isthen run on the computer with theresults as shown in Figures 2 and 3.Figure 2 shows the life production ofthe cow under the base conditions. Ascan be seen in the figure, the cow losesweight and the calving rate declinesuntil in the forth year she skips a calfand regains some of the lost weight.After this she again declines in weightand skips another calf in year seven.Figure 3 shows detail of the nutritionalsituation over the season. The linelabelled “1” is the predicted gain perday given the diet and forage nutrition.Line “2” is the gain which would bepredicted based only upon the phos-phorus content of the forage under theassumption that the other componentsof nutrition protein and energy werereadily available. Line “3” is thepredicted gain based on the proteinlevel and line “4” is the predicted gainbased on the energy level, againassuming the other components ofnutrition are available. The graphdemonstrates the fact that energy mustbe available for gain and that the othercomponents of gain combine withenergy to result in gain. At the start ofthe year energy is very low with theresult that the cow loses from one totwo pounds a day for the first threemonths of the year. For the next threemonths the energy availability improves

but the cow continues to lose weight atabout one quarter pound per day. Aftersix months the summer rains result innew forage and the cow gains weightuntil winter. During this four month timeof weight gain, it is clear from the graphthat while the cow has an excess ofenergy, protein levels and particularlyphosphorus levels are limiting factors inkeeping the cow gain below the gainpossible if the energy were fully utilized.

The economic results depend uponboth calf weights, which are simply afunction of the forage available be-tween calving and weaning, and uponthe calving percentage of the cow overher lifetime. For the base run thelifetime value of the cow’s productionexpressed in present dollars is 777dollars under conservative estimates ofcalf prices. This value will be used as ayardstick to judge alternative manage-ment strategies.

One possible reaction to the baseresults would be to check on thecorrespondence between forageavailability and nutritional needs of thecow. Figure 4 displays how the cow’snutritional requirements change overthe annual cycle. Requirements arehigh during the last trimester of preg-nancy and during the time the cow isnursing her calf. After the calf isweaned the requirements drop consid-erably. Comparing the requirements tothe results of the potential and actualgain chart result in the discovery thatgain is highest at the time of the yearwhere nutritional requirements arelowest. Since the requirements are tiedto breeding date, one possible alterna-tive to evaluate would be changing thebreeding date to September 1st inorder to better match up requirementsand forage availability. Figures 5 and 6display these results. The most obviousresult is that the cow maintains herweight for the seven years and doesnot skip any calves. The gain graphshows that weight losses are moder-ated for the winter months caused by


reducing the nutritive requirements ofthe cow during this period. The eco-nomic yardstick for this alternative is$1,128. This is improvement over thebase case of over 350 dollars allwithout any additional cost to therancher.

Another possibility suggested byanalysis of the base run is to removethe limitations on phosphorus duringthe period where it is limiting gain, bysupplementing from July 15th throughDecember 31st with a 6% phosphorusblock at the rate of .2 pound per dayand a cost of 20 cents per pound forthe supplement. The results of thissimulation are displayed in Figures 7and 8. A definite improvement inperformance over the base run can beobserved. The limitation of gain byphosphorus is significantly reducedresulting in higher gains and theeconomic yardstick adjusted for thecosts of the supplement, increases to964, over a 150 dollar improvement.

What about a more traditionalprogram of supplementation? Whathappens if we feed 1.5 pounds per dayfor 95 days beginning on November 1stof a 2% phosphorus, 25% protein and65% TDN supplement. The results aredisplayed in Figures 9 and 10. Thecows get fat. The calving rate thereforeincreases. The gains increase dramati-cally over the base run for the periodthe cows are being supplemented. Thegraph suggests that good use of theforage energy is being made with the

addition of the limiting factors ofphosphorus and protein to the cowsdiet. Most importantly the economicyardstick increases to 1,283 dollars,even after subtracting out the feedcosts, over a 500 dollar increasecompared to the base situation.

What about changing both the breedingdate and supplementing? What aboutchanging the timing of the supplemen-tation? What about .........? Therancher can continue the process ofevaluating alternatives quickly andcheaply by use of the computer simula-tion. Hopefully the computer resultswould lead to the selection of alterna-tives to further evaluate by real worldtesting and monitoring.

Conclusions

Ranchers in Arizona now have anew tool to help them evaluate deci-sions involving changes in range cownutrition. As data bases on diets andforage nutritive values are expanded,ranchers throughout the state will beable to quickly and efficiently evaluatealternative nutrition managementstrategies. For further information onthe Range Cow Nutrition Evaluatorcontact your County Extension Agent.

The authors are all members of theIntegrated Range Livestock Manage-ment team, College of Agriculture, TheUniversity of Arizona.

Extension Specialist, Department of Agricultural Economics 1

Range Management Specialist 2

Livestock Specialist 3

Cochise County Extension Agent 4

Cooperative ExtensionCollege of AgricultureThe University of ArizonaTucson, Arizona 85721


Figure 2

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec1

1 = Lehmann 2 = Phosphorus Percentage3 = Protein Percentage 4 = TDN Percentage

0.6000.00200

0.1501.00

0.4500.00150

0.1130.750

0.3000.001000.07500.500

0.1500.000500

0.03750.250

0.00.00.00.0

1.00

0.750

0.500

0.250

0.0

1 = Cow Weight 2 = Calf Weight 3 = Calving Percentage

CalvingPercentage

Figure 1

1200.00

900.00

600.00

300.00

0.0

Weight

Year

1 2 3 4 5 6 7


Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

4.00

2.00

0.0

-2.00

-4.00

Calving Date

Weaning DateBreeding Date

LactationThirdTrimester

ThirdTrimester

1 = Gain Day 2 = Gain Potential Phosphorus3 = Gain Potential Protein 4 = Gain Potential TDN

Figure 3

Figure 4


Breeding DateCalving Date

Weaning Date


ThirdTrimester

Seasonal Energy Requirements


1 2 3 4 5 6 7

1.00

0.750

0.500

0.250

0.0

1 = Cow Weight 2 = Calf Weight 3 = Calving Percentage Calving

Percentage

Year


Weaning Date

Third TrimesterLactation Lactation

Breeding DateCalving Date

4.00

2.00

0.0

-2.00

-4.00


Figure 6

Figure 5


Figure 7

1 2 3 4 5 6 7

1200.00

900.00

600.00

300.00

0.0

Weight1 = Cow Weight 2 = Calf Weight 3 = Calving Percentage

1.00

0.750

0.500

0.250

0.0

Year

CalvingPercentage

Figure 8


Calving Date

Breeding DateWeaning Date


ThirdTrimester

1 = Gain Day 2 = Gain Potential Phosphorus3 = Gain Potential Protein 4 = Gain Potential TDN4.00

2.00

0.0

-2.00

-4.00


1 2 3 4 5 6 7

1 = Cow Weight 2 = Calf Weight 3 = Calving Percentage

1.00

0.750

0.500

0.250

0.0

1200.00

900.00

600.00

300.00

0.0

WeightCalving

Percentage

Figure 9


ThirdTrimester


Lactation

Calving Date

Breeding Date Weaning Date

ThirdTrimester

4.00

2.00

0.0

-2.00

-4.00

Figure 10

Year


FROM:


Disclaimer



Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperationwith the U.S. Department of Agriculture, James Christenson, Director, Cooperative Extension, College ofAgriculture, The University of Arizona.



Range Cow Nutrition 1993 15

RANGE COW NUTRITIONIN LATE PREGNANCY

Edward LeViness 1

The success or failure of a cow-calfoperation depends on how well thecow’s nutritional requirements are metduring the last three months of preg-nancy.

In Arizona, the majority of cow-calfproducers manage their breeding herdsfor spring calving and the sale ofweaner calves in the fall. This is atraditional practice. It is logical andreflects experience gained from gen-erations of cattle ranching in thesouthwest.

The practice of spring calving, likenearly everything else in the cowbusiness, creates its own share ofmanagement problems. One of theseconcerns deals with the nutritionalrequirements of the breeding herdduring the winter months.

For the cow that has been bred to calvein February or March, or perhaps evenearlier, one of the most critical periodsin her yearlong productive cycle is theinterval between late Decemberthrough March. This time representsthe 7th, 8th and 9th months of preg-nancy or what is often referred to asthe third trimester of gestation. Unfor-tunately, however, this is the seasonwhen most forages reach their lowestnutrition. This is particularly true withprotein and carbohydrate levels and theproblem occurs with both grass andbrowse.

The graphs illustrate the relativenutritive values of grass and browsespecies found in the southwest:

It can be seen that grass and browsevary considerably in nutritive levelsthroughout the year. More importanthowever, from the standpoint of the

Shrubs

Grass

Grasses have lost: 85% of Carotene 75% of Protein 65% of Phosphorus

FastGrowth

Mature

Re

lati

ve A

mo

un

ts F

urn

ish

ed

Figure 1. Seasonal Trends in Protein, Phosphorus, and Carotene Content of Range Forage.

Am

ou

nts

Ne

ed

ed

April June Aug. Oct. Dec. Feb. April

Protein

Phosphorus

Carotene

Figure 2. Seasonal Trends in Calcium and Carbohydrates in Range Grass.

Carbohydrates

CalciumLeaching of Sugars, Starch, Etc.

Rela

tive

Am

ou

nts

Fu

rnis

hed

CHO

Am

ou

nts

Nee

ded

April June Aug. Oct. Dec. Feb. April

Ca


pregnant cow, is the fact that thenutritive levels of these forages areusually lowest during plant dormancy.This also happens to be a critical timefor the cow in the latter stages ofpregnancy.

To emphasize the importance ofnutrition in the cow and why this 80-90day period is so vital to her perfor-mance, consider a few of the dutiesexpected of the cow that are affectedby nutritional intake during this time:

With these thoughts in mind, it might begood for the producer whose breedingprogram is aimed at weaning a market-able calf from as many cows as pos-sible every 365 days, to check thearithmetic involved. The length ofgestation in most cows is between 275-290 days. Thus, a beef cow is preg-nant for most of the year! So, if theobjective is for the cow to calve every12 months, she has only 75-90 daysafter calving before she is pregnantagain. It is obvious there is little time towaste.

Consider then, the work the cow isexpected to complete, the time spanshe has to work in and the generally

inadequate nutritive levels of foragesshe grazes. It is evident that she willneed help.

One logical way to help the animalduring this important 80-90 day periodis to increase the nutrient level orquality of feed available. It is importantto understand this goal. Even underproper grazing management whereanimal numbers and their daily drymatter requirements are in balance withforage production, there are times whenforages will not provide the quality ofnutrition necessary to attain the live-stock performance level desired.

One of the most common and economi-cal methods of providing the cow withextra nutrition during her critical periodis by supplying what the industry refersto as a supplemental feed. The wordsupplement means something thatcompletes or makes an addition. Thisis what a supplemental feed is, anutritional additive that lends balanceand helps “round-out” the nutrientsprovided by range forages.

Supplemental feeds are not designednor should they be expected to sub-stantially replace dry matter, roughageof range forages or both. (This doesnot consider true range feed emergen-cies, wherein the role of supplementalfeeds may be altered temporarily.)Most supplemental feeds containvarying quantities of the nutrientsprotein, carbohydrate, minerals andvitamins.

The questions and details concerningthe what, where and when of supple-mental feeding represent subjects inthemselves and are not dealt with here.

The purpose of this material is toremind stockmen of the vital functionsthat must take place in the cow duringthe latter stages of her pregnancy andthe part adequate nutrition plays inthese functions. It’s up to the rancherto insure that the nutritional needs ofthe cow during this critical time are met.

a) she must adequately nourish the developingunborn calf because it triples in weight duringthe last 3 months of gestation,

b) her thriftiness and body condition must bemaintained in order to promote normal calving(weak cows produce weak calves or nocalves at all),

c) the cow must insure an adequate supply ofmilk for the newborn calf,

d) she needs to maintain good health to minimizethe interval between calving and first heatafter calving,

e) she should stay in good condition to increasethe likelihood of conception during the first orsecond heat period after calving.


FROM:


Disclaimer





Livestock Specialist 1 (Retired)Cooperative ExtensionCollege of AgricultureThe University of ArizonaTucson, Arizona 85721



1) a current weight for a mother cowand a target weight for that cow 12months in the future

2) expected nutrient analysis for rangeforages over the year

3) nutrient analyses and costs forpossible supplements what is theleast cost supplement plan toinsure that the mother cow meetsor exceeds her target weight?

This is an extension of the least costration problem described earlier and usesthe same basic spreadsheet techniquesto solve the problem. The major differ-ence is that instead of constraints on nutri-ents in the ration we now have constraintson cow weight. To do this we need a wayof predicting cow weights. The methodused is a modified net energy method.The modifications were to add mineralsand protein to the gain formula and tovary the energy requirements as a func-

LEAST COSTSUPPLEMENTATION

Russell Gum1

Supplementation decisions are one ofthe critical tasks in managing a range cowherd. Should I supplement? Whenshould I supplement? What should Isupplement? These are all common andimportant questions that a rancher mustanswer. The purpose of this report is todescribe a decision aid that can help inanswering these questions. A copy of thedecision aid in Excel spreadsheet formatcan be obtained from the author.

The question answered by this decisionaid is given:

123456789

1 01 11 21 31 41 51 61 71 81 92 02 12 22 32 42 52 62 72 8

A B C D E F G H I J K L M N

Month 1 2 3 4 5 6 7 8 9 10 11 12cow weight lbs 800 790 781 774 773 798 824 835 832 821 811 800pg_energy_req ratio 1.32 1.6 1.6 1.6 1.6 1.6 1.49 1.38 1.25 0.95 0.95 1.12

Calve Breedlbs energy lbs/day 6.00 5.92 5.86 5.82 5.87 6.07 6.23 6.28 6.24 6.16 6.08 6.00pounds_protein lbs/day 0.75 0.74 0.73 0.73 0.77 0.80 0.80 0.79 0.78 0.77 0.76 0.75pounds minerals lbs/day 0.00 0.00 0.00 0.01 0.04 0.04 0.03 0.01 0.00 0.00 0.00 0.00

net energy for maintenance lbs/day 6.24 5.76 5.29 4.76 3.61 3.70 4.47 5.32 6.43 6.37 6.30 6.24net energy for gain lbs/day -0.24 0.17 0.57 1.06 2.26 2.37 1.76 0.96 -0.19 -0.21 -0.23 -0.24

gain-energy lbs/day -0.12 0.09 0.31 0.62 1.63 1.66 1.06 0.51 -0.09 -0.10 -0.11 -0.12gain-minerals lbs/day -0.99 -1.05 -1.12 -0.89 1.77 2.02 0.46 -0.74 -1.04 -1.02 -1.01 -0.99gain-protein lbs/day -0.22 -0.23 -0.23 -0.24 -0.23 -0.27 -0.30 -0.30 -0.25 -0.24 -0.23 -0.22

expected gain lbs/day -0.35 -0.29 -0.22 -0.06 0.84 0.87 0.36 -0.09 -0.36 -0.36 -0.35 -0.35

cost $/month 2.00 2.00 2.00 2.15 3.15 3.25 2.77 2.25 2.00 2.00 2.00 2.00

cost per year 27.56

range forage lbs consumed 15.00 14.80 14.64 14.52 14.49 14.96 15.45 15.65 15.60 15.40 15.20 15.00hay lbs fed/day 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00cottonseed lbs fed/day 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00block lbs fed/day 0.00 0.00 0.00 0.02 0.15 0.17 0.10 0.03 0.00 0.00 0.00 0.00mineral supplement lbs fed/day 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Figure 1


tion of the pregnancy and lactation state ofthe cow.

Because of the added complexity of thismodel compared to the simpler ration for-mulation model, not all spreadsheet solv-ers will solve this problem. You may haveto experiment with the solver option inyour spreadsheet to check if it works. Thetemplate is available in Excel format andthe Excel solver does solve this problemalbeit slowly. If you would like currentinformation on what spreadsheets cansolve this problem you might considerposting a question to the IRM electronichighway mailing list. (See the Ranchers’Management Guide article on the elec-tronic highway information sources for de-tails on how to do this.)

The basic spreadsheet is displayed inFigures 1 and 2.

How to use the supplement decision guide.

1. Input the starting weight of yourcows in cell C3.

2. Input the expected nutrient valuesand costs for your range forage inrows 30 through 33. This is not atrivial task as the species composi-tion of the diet as well as the nutri-ent values of the components ofthe diet vary over the year. How-ever, insight can be gained into thesupplement problem by inputting areasonable estimate of these val-ues based on your experience orperhaps information from exten-sion, blm, forest service or soil con-servation service range manage-ment professionals.

3. Input the nutrient values and costsfor the possible supplements youwould like to consider. Commer-cial supplements have this infor-mation on their tags. Values forother feeds such as hay and cot-tonseed can be obtained for yourlocal extension agent.

Set all of the supplement fed cells(C25:N28) to zero. At this point the

2 93 03 13 23 33 43 53 63 73 83 94 04 14 24 34 44 54 64 74 84 95 05 15 25 35 4

A B C D E F G H I J K L M N

range forage % protein 0 .05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05% energy 0 .40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40% phosphorus 0 .00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00$/au day 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07

hay % protein 0 .12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12% energy 0 .55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55% phosphorus 0 .00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00$ / l b 0 .05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05

cottonseed % protein 0 .20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20% energy 0 .50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50% phosphorus 0 .01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01$ / l b 0 .15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15

block % protein 0 .30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30% energy 0 .50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50% phosphorus 0 .05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05$ / l b 0 .25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25

mineral supplement % protein 0 0 0 0 0 0 0 0 0 0 0 0% energy 0 0 0 0 0 0 0 0 0 0 0 0% phosphorus 0.185 0.185 0.185 0.185 0.185 0.185 0.185 0.185 0.185 0.185 0.185 0.185$ / l b 0 .2 0 .2 0 .2 0 .2 0 .2 0 .2 0 .2 0 .2 0 .2 0 .2 0 .2 0 .2

Figure 2


spreadsheet will calculate the ex-pected results for the scenariowhere no supplement is fed. Youmust analyze this result by inspec-tion and common sense to see ifthe result is what you would expectto happen if you did not feed anysupplement to your cows. If theresults are about what your experi-ence and common sense wouldexpect to happen if no supplementwere fed then you can proceed tothe next step. If not, this problemneeds to be fixed before you pro-ceed. The most likely cause for thespreadsheet model and reality tobe different is the intake of rangeforage amount. This value is ini-tially set at 1.875% of the cowsweight. This value varies as a func-tion of the quality and availability offorage on your range. If your judg-ment indicates your cows shouldnot gain as much as the originalspreadsheet model indicates for aparticular month you need to lowerthe intake percentage in the appro-priate cell. For example if youexpect that the November weightgain indicated is too high edit cellM24 and replace the .01875 in theformula with a lower number. Thespreadsheet will now recalculateand the new results can be in-spected. When you are satisfiedthat the results reflect what wouldhappen on your ranch you are readyfor the next step.

4. Check to see if the Decemberweight meets your targetweight. If it does then theproblem is solved withoutany supplement. If not youneed to follow the next stepsto calculate a least costsupplement plan.

Choose Solver from the for-mula menu. The followingdialog box should appear(Figure 3). If solver does notappear in your menu openthe solver add-in the Solver

sub-directory of the Macro Librarydirectory.

Set cell is the cell the solver willattempt to minimize (or maximizedepending on which check box ischecked) subject to the con-straints. In our case B21 is the cellthat contains the total feed cost forthe cow for the year.

By changing cells contains all ofthe things the program can ma-nipulate in its search for an opti-mum solution. In our case it is thearea where the timing and amountsof supplement will be reported.i.e., C25 TO N28.

Subject to the constraints con-tains all of the restrictions placedon the solution of the problem. Inour case there are three basicconstraints. First it is not possibleto feed negative amounts ofsupplement so cells C25 to N27must be equal to or greater thanzero. Second we want to meet thetarget weight for the cow N3. Fi-nally we want to insure that thecows are gaining at least .5 poundsper day in the period just beforeand during the breeding season.To do this we constrain H17 to begreater than or equal to .5. If youhave a different breeding sched-ule than the example you will haveto adjust this constraint and adjustthe pregnancy energy require-ments (row 4).

Figure 3


After checking to be sure the setcell, by changing cells and subjectto constraints settings are correctclick on the solve button. It will takea while for the problem to solve. Infact, it may indicate you havereached the time limit. If this hap-pens just click on continue and letit run a few more minutes. When itfinishes click on the option to dis-play the results on the originalspreadsheet. Now you should savethe results and then analyze whatthe computer suggested as asupplement plan. Below is the rec-ommendations from the sampleproblem. The optimal results aredisplayed in Figure 1, rows 25, 26,27, and 28.

The computer’s suggestions meetall of the constraints, and are theleast cost manner of doing so. Butyou will probably want to use a bitof common sense to modify thecomputers suggestions. For ex-ample, the sample results suggestfeeding .02 pounds of block perday per cow in April (cell F27 -Figure 1). Common sense wouldsuggest that this would be moretrouble than it was worth. Onepractical solution would be to feed.17 pounds of block per day percow in May and none in April in-stead of the recommendedamounts. If you enter this into thespreadsheet you can check to seethat you still meet constraints. Otherminor modifications in thecomputer's recommendations mayslightly raise costs or cause theconstraints to be not quite met. Byputting these practical modificationsinto the spreadsheet and observ-ing their impact on costs and con-straints a practical supplement plancan be generated.

SUMMARY

The supplement recommendation spread-sheet can produce useful information tohelp you develop a sound supplementplan. The computer model is only a tool tohelp you think about supplement man-agement. It is not an exact answer to befollowed no matter what. The functionalrelationships between nutritional intakeand gain are statistically derived approxi-mations. The nutritional values for yourrange forage will be subject to weatherand other random influences. The intakeof range forage is an approximation.However, even with the uncertainties in-volved in the model it can serve as areasonable starting point for your supple-ment decisions As with any other ranch-ing decision monitoring is necessary. Ifyou happen to get great weather and thegrass is much taller and greener on yourrange than it was depicted in the spread-sheet you will need to reevaluate yoursupplement planning. The spreadsheetmodel can, and should be used through-out the year. Adjustments to the intakefunction and the nutritional values of therange forage can be made to reflect ac-tual conditions. The model can then berun allowing the remaining months supple-ment plan to vary to provide informationon possible revisions in your supplementplan. To do this you would need to changethe By changing cells selection underthe Solver menu.

While it will take effort to set up the modeland get it initially running it will get easierwith time. As you use the model anddevelop information on the nutritionalvalues obtained by your cows from therange forage on your ranch you will beable to fine tune it to your specific ranch-ing conditions.

Extension Specialist1

Department of Agricultural and Resource EconomicsCollege of AgricultureThe University of ArizonaTucson, Arizona 85721


FROM:


Disclaimer




The University of Arizona College of Agriculture is an Equal Opportunity employer authorized to provideresearch, educational information and other services only to individuals and institutions that functionwithout regard to sex, race, religion, color, national origin, age, Vietnam Era Veteran's status, orhandicapping conditions.



INTRODUCTION

Animal learning has been shown toplay a major role in the development ofdiet selection by domestic ungulates.Dr. Frederick Provenza and hisassociates at Utah State Universityhave conducted a series of experi-ments over the past 15 years to learnhow physiological and behavioralmechanisms govern diet selection. Inthis paper, we synthesize several keydiet selection concepts presented in 4recent articles (i.e., Provenza et al.1992; Provenza 1995, 1996, 1997).

PALATABILITY AND PREFERENCE

Palatability is traditionally defined as“the relish an animal shows for aparticular plant as forage…whichvaries with succulence, fiber content,nutrient and chemical content, andmorphological features such as spinesand thorns” (see Frost and Ruyle, thisGuide). Because palatability is defined interms of plant attributes, it is often calleda “plant characteristic.” Preferenceis traditionally defined as “relativeconsumption of one plant over anotherby a specific class of animal whengiven free choice at a particular timeand place” (Frost and Ruyle, thisGuide). Because preference is definedin terms of free choice by an animal, itis often called an “animal characteristic.”Collectively, these two definitionsevoke range animals’ well-documentedability to somehow assess the nutri-tional value of range forages (i.e.,palatability), and invariably select amore nutritious diet than is availableon average within their particularenvironment (i.e., preference). In

GLOSSARY OF TERMS

Affective Processes – Involuntary processes that do not require conscious thought. For example, breathing,digestion, and hedonic shifts are affective (involuntary) processes that occur even while an animal sleeps oris anesthetized. See cognitive processes and hedonic shift.

Cognitive Processes – Voluntary processes that require conscious thought. For example, walking, running,or seeking/selecting a particular food are cognitive (voluntary) processes. See affective processes.

Emetic System – System responsible for nausea, vomiting, and malaise in animals. It is a critical componentof the affective (involuntary) system and plays a key role in the formation of conditioned taste aversions toforages that cause malaise. See affective processes, malaise.

Hedonic Shift – A shift in preference (i.e., either increased or decreased intake) for a food following positiveor negative postingestive feedback. See affective processes and postingestive feedback.

Malaise – Negative postingestive feedback. Feeling of malaise (i.e., nausea or unpleasant feelings of physicaldiscomfort) after ingesting a food or foods. See postingestive feedback, satiety.

Postingestive feedback (PIF) – Feedback from the gut to the brain that allows animals to sense the nutritionalor toxicological effects of food ingestion (positive or negative) and accordingly adjust their preference(increase or decrease intake) for the food. See hedonic shift, malaise, satiety.

Satiety – Positive postingestive feedback. Feeling of satisfaction after ingesting a food or foods. See malaise,postingestive feedback.

HOW DO DOMESTICUNGULATES SELECT

NUTRITIOUS DIETS ONRANGELANDS?

Larry D. Howery1, Frederick D.Provenza2, and George B. Ruyle3


Figure 1. Schematic representation of affective and cogni-tive processes in diet selection. The affective system linksthe taste of food with its postingestive feedback (PIF). Thecognitive system integrates the senses of taste, smell, andsight which animals use to seek or avoid foods in accord withpositive or negative PIF. There is an iterative exchange ofinformation between these systems which allows animals tomodify their foraging behavior in response to changingenvironmental conditions, and in response to changingnutritional needs (adpated from Provenza et al., 1992).4

addition to selecting nutritious diets,range animals generally avoid plantsthat cause toxicosis, inhibit digestion, orcause malnutrition. This is remarkablegiven that nutrients, toxins, and digestioninhibitors vary seasonally and bylocation, both among and within plantspecies. Animals do occasionally over-ingest plant nutrients and toxins(discussed later), but generally speaking,range herbivores commonly selectforages that meet their nutritionalneeds and avoid forages that do not.Although this observation has beenoften reported in the literature, Dr.Provenza’s research is the first to offerboth theoretical and experimentalevidence that explains how this impor-tant process occurs. His work suggeststhat animal preference for foods (andhence their palatability) are bestunderstood as the interrelationshipbetween a food’s taste and itspostingestive effects, which is deter-mined by a food’s chemical (andphysical) characteristics, and by an

animal’s age, morphology, and physi-ological condition.

POSTINGESTIVE FEEDBACK (PIF)AND HEDONIC SHIFTS

Animals regulate their intake of foragesaccording to whether postingestivefeedback (PIF) that results from forageingestion is positive or negative.Animals change their “preference” forvarious forages (i.e., forages becomemore or less “palatable” and relativelymore or less “preferred”) in accord withPIF. This process is know as ahedonic shift. For example:

. Lambs develop strong preferenceseven for poorly nutritious foodssuch as straw (i.e., increasedintake, a positive hedonic shift)when it is eaten during stomachtubings of energy (starch or glu-cose) or nitrogen (urea, casein,gluten).

. Conversely, lambs quickly learn toavoid a previously palatable food(i.e., decreased intake, a negativehedonic shift) after receiving onedose of lithium chloride (LiCl), acompound that causes nausea.

These results demonstrate that palat-ability and preference can be manipu-lated experimentally. However, palat-ability and preference are also alteredin nature when chemical composition ofrangeland plants (i.e., forage quality)changes across space (e.g., rangesites differing in kind and amount ofavailable forage) and time (e.g., declinein forage quality as plants mature).

AFFECTIVEAND COGNITIVE SYSTEMS

Two interrelated systems mediatehedonic shifts via PIF from the gut tothe brain: affective systems andcognitive systems. Affective involun-tary processes are mediated subcon-sciously; cognitive processes are


mediated consciously. The senses oftaste, smell, and sight are linked withPIF across the two systems, but arefunctionally different (Figure 1). We willdiscuss affective and cognitivesystems (and their affiliated senses)separately in order to highlight theirprimary functions, but this does notmean they operate independently ofone another. Animals readily exchangeinformation between these twosystems through their senses of taste,smell, and sight.

Affective (involuntary) processesallow animals to associate the taste offorages with their positive or negativePIF and respectively form eitherconditioned preferences or conditionedaversions. If a forage causes malaise(i.e., nausea), animals acquire condi-tioned taste aversions (mild to strong).Malaise may occur when the forageingested contains excess nutrients(e.g., energy, protein, minerals), excesstoxins (e.g., tannins, alkaloids), orinadequate nutrients (Figure 2). Whatconstitutes excesses and deficits innutrients or toxins depends on theanimal’s age, morphology (e.g., smallvs. large animal, ruminant vs. cecaldigestive system), and physiologicalcondition (Figure 3). On the other hand,if a forage causes satiety (the sensationof being satisfied to the full), animalsacquire conditioned taste preferences(mild to strong). Satiety results whenan animal ingests the kinds andamounts of forages necessary to meetits nutritional requirements, againdepending on age, morphology, andphysiology.

Cognitive (voluntary) processesallow animals to integrate the senses oftaste, smell, and sight to discriminateamong forages and make “conscious”choices (i.e., behavioral modification) toselect or avoid a food based on previ-ous experience with the food’s PIF(Figure 1). If a food previously resultedin malaise (i.e., negative PIF), its tastebecomes undesirable and the animaluses its senses of smell and sight to

Figure 2. Preference is dependent on how adequately a foodsatisfies an animal’s particular nutritional requirements. Pref-erence resides along a continuum, wherein foods with low orexcessive concentrations of nutrients (or excessive concen-trations of toxins) cause preference to decline, and foods withadequate amounts of nutrients cause preference to increase(adapted from Provenza 1995).4

Figure 3. Animal nutrient requirements vary with age andphysiological condition. The ideal nutritional state (centerline) occurs when all nutrients are obtained simultaneously.It is dynamic and multidimensional, with as many dimen-sions as there are functionally relevant nutrients. However,animals need not maximize (optimize) intake of any particu-lar nutrient or mix of nutrients within each meal or even on adaily basis, because they can withstand departures from thenormal average intake of nutrients (i.e., energy-rich sub-stances, nitrogen, various minerals, and vitamins). Rather,homeostatic regulation needs only some increasing ten-dency, as a result of a gradually worsening deficit of somenutrient (lower line) or of an excess of toxins or nutrients(upper line), to generate conditions (i.e., malaise) to correctthe disorder (i.e., cause the animals to change food selec-tion). Malaise causes animals to increase diet breadth, toacquire preferences for foods that rectify states of malaise,and to exhibit state-dependent food selection (adapted fromProvenza 1995).4


avoid the forage in the future; theconverse would occur if a food previ-ously resulted in satiation (i.e., positivePIF).

To summarize, animals use the affec-tive system to evaluate thepostingestive consequences of ingest-ing a forage, and the cognitive systemto modify their foraging behavioraccording to whether PIF was positiveor negative. Although animals integratethe senses of taste, smell, and sight toseek or avoid foods that have respec-tively caused positive or negative PIF,taste is most strongly linked with PIF.Animals first relate the taste of a foodwith its PIF through the affective(involuntary) system before smell andsight become functional in the cognitive(voluntary) system (Figure 1). Hence,foraging behavior entails a never-ending exchange of information systemswhereby animals sample forages,associate positive or negative PIF fromthe digestive tract with a forage’s taste,integrate forage taste with smell andsight, and then seek or avoid foragesaccordingly. Together, these twosystems give animals flexibility to learnand modify their foraging behavior inresponse to changing environmentalconditions (e.g., variation in plantnutrients and toxins across space andtime), and in response to changingnutritional needs (old vs. young,lactating vs. non-lactating, etc.).

CONDITIONED TASTE AVERSIONS

Conditioned taste aversions haveevolved as a survival mechanism tohelp animals limit their intake of other-wise nutritious plants that containtoxins, or plants that fail to meetnutritional requirements. Supportingthis notion is the fact that conditionedtaste aversions have been demon-strated in many different animal species(e.g., snakes and tiger salamanders;quail, blackbirds, blue jays, and crows;rats, opossums, and mongooses;coyotes and timber wolves; goats,

sheep, and cattle; olive baboons andhumans) using a variety of compounds.The emetic system is a critical compo-nent of the affective system (seeprevious section), and plays a key rolein the formation of conditioned tasteaversions to forages that cause mal-aise. The emetic system mediatesinteractions between the brain and thedigestive tract and is the same systemresponsible for nausea and vomiting inhumans.

Because the emetic system is a subsetof the affective system, it involves non-cognitive or involuntary processes.Accordingly, aversive PIF may occureven as an animal sleeps, is anesthe-tized, or with short (i.e., less than 1hour) or long delays (i.e., up to 12hours) between food ingestion and PIF.This is critical because digestion andabsorption rates (i.e., PIF) vary fromfast to slow depending on animalspecies and forage characteristics.Although conditioned taste aversions(and preferences, discussed nextsection) are non-cognitive, this informa-tion is clearly integrated with thecognitive system through the senses ofsight and smell. After animals relate aforage’s taste with negative PIF (mal-aise), smell and sight become powerfulpredictors of anticipated negative PIFand the cognitive response is to avoidthe forage when encountered in thefuture (Figure 1). The emetic systemmay be stimulated (resulting in malaiseand conditioned taste aversions) whenanimals ingest forages containingexcess nutrients or toxins. There is alsolimited evidence that the emetic systemmay be stimulated when foragesingested contain inadequate nutrients(Figure 2). Some experimental andanecdotal examples of conditionedtaste aversions follow.

EXCESS NUTRIENTS

. Ruminants prefer high-energyfoods like grains, but limit grainintake and increase intake ofalternative foods once grain is over-


ingested, evidently becausenegative PIF caused by excessby-products from microbial fermen-tation (i.e., volatile fatty acids suchas lactate, acetate, and propionate)produces a negative hedonic shiftwithin a meal.

. Sheep given a high dose of propi-onate during a meal (i.e., highenergy) acquire a persistentaversion to the food.

. Ruminants eating foods high inrumen-degradable protein (throughmicrobial fermentation) experiencetoxic levels of ruminal ammoniawhich cause declines in intake.

. Goats learn to limit intake ofvarious sources of non-proteinnitrogen within minutes of inges-tion. For instance, urea is quicklyconverted into ammonia, whichexplains why intake rapidly declinesas urea is added to foods.

. Sheep fed an oat hay-lupinemixture containing either 0, 1.7,3.3, 6.3, 12, or 21% of a mineralmix ate less as the mineral concen-tration was increased. Most of thesheep consuming the highestmineral concentrations eventuallyrefused to eat the food.

EXCESS TOXINS

. Goats prefer old-growth to current-season growth blackbrush(Coleogyne ramosissima) twigs,even though current-season growthcontains more nitrogen (2.3 vs.1.7%) and is more digestible (48vs. 38%) than old-growth. This isbecause current-season growthcontains a condensed tannin thatcauses aversive PIF.

. Toxic compounds in larkspur(Delphinium barbeyi) and tallfescue (Festuca arundinacea)(alkaloids), brassica crops(glucosinolates), and sacahuista

(Nolina microcarpa) (saponins,coumarins, furocoumarins, andanthraquinones) cause decreasedintake in cattle, sheep, and goats.

. Various toxic compounds in leafyspurge (Euphorbia esula), bitter-weed (Hymenoxys odorata), poorquality silage, and sagebrush(Artemisia spp.) contain com-pounds that decrease intake inrange herbivores.

. Sheep quickly acquire aversions tofoods containing the toxin lithiumchloride (LiCl).

INADEQUATE NUTRIENTS

. Deficits or imbalances of energy,nitrogen, and amino acids causelambs and rats to decrease intake.

. Phosphorus deficient diets causecattle, sheep, and goats to decreaseintake; the decline in intake isdirectly related to the degree of thedeficit.

CONDITIONED TASTEPREFERENCES

Conditioned taste preferences, likeconditioned taste aversions, aremediated through the affective andcognitive systems, except of course,the cognitive response of animals is toseek forages that have previouslycaused positive PIF (Figure 1). Animalsmay form preferences and seekforages when their taste has beenpaired with adequate: 1) energy, 2)nitrogen, or 3) recovery from nutritionaldeficiencies or malaise. Some experi-mental and anecdotal examples ofconditioned taste preferences follow.

ENERGY AND PROTEIN

. Lambs acquire strong preferencesfor non-nutritive foods (e.g., strawor grape pomace) or flavors (e.g.,maple, apple, coconut, onion)


paired with energy sources (e.g.,starch or glucose) or with volatilefatty acids (e.g., propionate oracetate) that are energy sources.

. Lambs also acquire strong prefer-ences for flavored straw paired withprotein (e.g., casein, gluten) or

non-protein (e.g., urea) sources ofnitrogen.

. Lambs acquire the strongestpreferences when the sources ofenergy and nitrogen ferment atsimilar rates and in similaramounts in the rumen. Conversely,when the balance of energy andprotein is skewed in rate oramount, animals tend to formaversions to the food.

. Energy and protein can both readilychange preferences, but animalsrequire much more energy thanprotein each day (Figure 4).Accordingly, animals typicallyacquire stronger preferences fornon-nutritive foods paired withenergy than with protein. However,meal to meal preference for energyand protein depends on whetherenergy and protein requirementswere satisfied during previousmeals. After a high-energy meal,lamb preference for energy declinesand preference for proteinincreases; the converse is also true(Figure 5).

RECOVERY FROM NUTRITIONALDEFICIENCIES

. Lambs suffering from acidosis(excess energy) drink more of asodium bicarbonate solution; lambsnot suffering from acidosis preferplain water.

. Cattle readily consume supplemen-tal protein blocks when ingestingforages low in protein.

. When browsing a low-proteinblackbrush diet (1.5% nitrogen),goats consume woodrat housessoaked in urine (nitrogen).

. Sheep increase intake of a protein-deficient diet following infusions ofprotein into the duodenum.

Figure 4. Animals require more energy daily than any othernutrient. For example, a 40 kg lamb requires 1160 g of totaldigestible nutrients (TDN), but only 202 g of crude protein(CP), 7.7 g of calcium (Ca), and 3.9 g of phosphorus (P) to gain345 g/d (3/4 lb/d) (NRC 1985).

Figure 5. Animals typically acquire stronger preferences fornon-nutritive foods paired with energy than with protein. How-ever, meal to meal preference for energy and protein dependson whether energy and protein requirements were satisfiedduring previous meals. After a high-energy meal, lamb prefer-ence for energy declines and preference for protein increases;the converse is also true.

Nutrient Requirements in Perspective: animalsrequire more energy than any other nutrient

Calcium (7.7g) Phosphorus (3.9g)

Crude Protein (202 g)

Lamb: 40 kg (88 lb)Gain: 345 g/d (3/4 lb/d)

Total DigestibleNutrients (1160 g)


. Rats prefer flavors associated withtheir recovery from threonine (anamino acid) deficiency.

. Sheep apparently rectify mineraldeficits (e.g., P, S, and Se) byingesting mineral supplements;cattle consume non-food items,apparently to rectify P deficiencies.Deer and other ungulates experi-encing mineral deficits eat antlers.Bighorn sheep that use rodentmiddens as mineral licks may do soto rectify nutrient deficiencies.

. Cattle ingesting mineral deficientforages lick urine patches of rabbitsand man, chew wood, consumesoil, eat fecal pellets of rabbits, andingest non-food items such asplastic, feathers, bones, cinders,sacks, and tins. Mineral deficientcattle also eat rabbit flesh andbones, whereas non-deficientanimals may sniff or lick the flesh,but never eat it, and they ignore thebones.

. Other ruminants experiencingvarious nutrient deficiencies havebeen known to eat the following:live and dead lemmings, rabbits,birds (caribou, red deer, sheep),ptarmigan eggs (caribou), arcticterns (sheep), and fish (white-taileddeer).

SAMPLING FAMILIARVS. NOVEL FORAGES

Animals may frequently change intakeof familiar foods in familiar environ-ments because the nutrient and toxincontent of familiar plants can changedramatically within a matter of hours oreven minutes depending on previousherbivory and/or environmental condi-tions. If toxicity decreases (or nutrientcontent increases), the food is nolonger paired with negative PIF andintake may increase. Conversely,forage intake may decrease as forage

toxicity increases or as nutrient contentdecreases. Thus, forage sampling andPIF provide animals with a means oftracking and adapting to changes innutrients and toxins in familiar foragingenvironments.

Animals sample new (novel) forageseven more cautiously than familiarforages evidently because thepostingestive consequence of ingestinga new forage is unknown. Animals areapt to “blame” a novel food for negativePIF even when it is not responsible forthe malaise. For instance, younganimals that were given LiCl (i.e.,negative PIF) avoided a novel foodwhen fed a combination of one nutri-tious-novel and four nutritious-familiarfoods even though one of the familiarfoods actually contained the LiCl.“Blaming” novel rather than familiarforages for aversive postingestiveconsequences likely evolved as ameans of protecting herbivores fromover-ingesting potentially harmful newfoods before confirming their PIF (i.e.,positive or negative) by carefulsampling as described above.

Thus, range herbivores routinelysample both nutritious and toxicforages (both familiar and novel) andregulate forage intake according towhether PIF is positive or negative. Inaddition to sampling and PIF, differentanimal species have evolved special-ized physiological mechanisms thatbind, metabolize, or detoxify certainthresholds of harmful plant compounds.However, the capacity of these mecha-nisms is seldom exceeded becauseanimals quickly acquire taste aversionsand limit intake before toxicosis en-sues. Physiological mechanisms workin concert with PIF, and provide ani-mals flexibility to regulate their intakeand ingest adequate diets in ever-changing foraging environments. Thisis impressive considering the millions ofbites that range herbivores take eachday across rangelands that contain adiverse array of nutritious and harmfulplant compounds.


WHY DO ANIMALSSOMETIMES OVERINGEST

NUTRIENTS AND/OR TOXINS?

Animals occasionally over-ingest plantnutrients and toxins that may causedeclines in intake, production, and evendeath. This probably occurs wheneveran animal fails to properly relate thetaste or smell of a particular forage withits PIF, and the animal’s physiologicalmeans for binding, metabolizing, ordetoxifying toxic compounds isexceeded. Any of the followingscenarios (or combinations thereof)involving both the affective and cognitivesystems could be responsible for sucha breakdown.

EMETIC SYSTEM NOT STIMULATED

The emetic system apparently must bestimulated (i.e., malaise must beexperienced by animals) to produce aconditioned taste aversion. However,over-ingestion of certain nutrients andtoxins may not stimulate the emeticsystem.

. Animals that over-ingest alfalfaexperience bloat and decreaseshort-term intake, apparentlybecause tension receptors in therumen and reticulum are stimu-lated which may cause short-termphysical discomfort. However,bloat apparently does not stimu-late the emetic system or cause along-term negative hedonic shiftbecause animals will ingest alfalfasoon after bloat subsides. Incontrast, forages that stimulate theemetic system (cause malaise)have been avoided for at least 3years.

. Some toxic compounds (e.g.,tannins) stimulate the emeticsystem and cause conditionedtaste aversions. Other compounds(e.g., gallamine, naloxone) may notstimulate the emetic system but

instead cause aversions to physicallocations or other external stimuli.

INTERACTIONS BETWEENAVERSIVE AND POSITIVE PIF

Animals are more likely to be poisonedwhen PIF from a toxin is not experi-enced for more than 12 hours. Beyond12 hours, animals may not be able todistinguish which foods cause positiveor negative PIF. The longer the delaybetween food ingestion and aversivefeedback, and the higher proportion ofpositive to negative PIF during thattime, the more likely it is that livestockwill continue to ingest the food.

. Some animals may die from over-ingesting larkspur (D. barbeyi)because there is immediate posi-tive PIF but delayed aversive PIF.For instance, cattle ingest larkspurbecause it initially enhancesruminal fermentation and digestion(i.e., it is high in energy and protein).Consumption generally increasesover a 2 to 4 day period beforedeclining dramatically when alka-loids have their maximum aversiveeffects. A somewhat similar sce-nario may occur when animalsover-ingest alfalfa and becomebloated. Positive PIF from nutrientsmay cause a strong liking for anutritious food like alfalfa (i.e., apositive hedonic shift) that over-rides any short-term physicaldiscomfort (i.e., stimulation oftension receptors in the rumen andreticulum) due to bloat.

. Poisoning is delayed when animalsconsume various locoweed species(Astragalus and Oxytropis spp.)that contain indolizidine alkaloids.Cellular damage does not occur for8 days and there are no clinicalsigns of poisoning for 3 weeks.Animals acquire aversions to suchfoods only after vital organs (e.g.,the liver) have been damaged.


. Liver damage caused bypyrrolozidine alkaloids in speciessuch as groundsel (Senecio spp.) isprogressive and death may notoccur for months or even years.

DIFFERENTIATING NUTRITIOUSFROM TOXIC PLANTS INUNFAMILIAR ENVIRONMENTS

It is probably more difficult for herbi-vores to differentiate nutritious fromtoxic foods in unfamiliar environmentsbecause all foods may be novel.

. Ninety percent of naïve goatsintroduced into pastures containingwhite snakeroot (Eupatoriumrugosum) died during the first 2weeks of grazing. Survivorsapparently learned to avoid theplant.

. Sheep in South Africa eat groundselfor the first 3 days in an unfamiliarpasture but then refuse to eat theplant even if starving.

. Cattle ranchers in South Africastomach-tube a sublethal preparationof tulips (Homeria pallida) toprevent deaths, and report that onlynaïve or extremely hungry animalseat the plant. Naïve animals giventhe preparation, or untreatedanimals that survive beyond 4 daysof grazing pastures containing theplant learn to avoid tulips.

. Many cattle deaths caused bylarkspur (D. barbeyi) occur within10 to 14 days after cattle enter anew pasture. Survivors may learnto avoid ingesting a lethal dose.

. When foraging in a familiar environ-ment, sheep ate less of a familiar-aversive food than in an unfamiliarenvironment. Conversely, whenforaging in an unfamiliar environ-ment, sheep ate less of a novel-harmless food than when in a

familiar environment. These resultssuggest that animals generallyperform better when foraging onfamiliar foods in familiar environ-ments.

CHANGES IN ENVIRONMENTALCONTEXT MAY ALTER ANIMALPHYSIOLOGY

Even when familiar plants are availablein unfamiliar environments, changes inan animal’s environmental context mayrender its physiological mechanisms(e.g., binding, metabolizing, anddetoxifying) less effective and causeanimals to be more susceptible totoxicosis. In this case, the same doseof a familiar toxin may be more harmfulin an unfamiliar than in a familiarenvironment. Work in this area hasmainly involved drug research onhumans and rats, but there are impor-tant implications concerning how rangeanimals may respond to familiar toxicplants after being moved to an unfamiliarenvironment.

. A cancer patient died when injectedwith morphine in a different room;the patient had tolerated the samedose when injected every 6 hoursfor 4 weeks in a familiar room.

. Social drinkers become moreimpaired when they drink at unusualtimes or in different settings.

. Rats with or without previousexperience with heroin were givena strong dose either in a familiar ora unfamiliar environment. The dosewas lethal for:

. 32% of the experienced rats ina familiar environment.

. 64% of the experienced rats inan unfamiliar environment.

. 96% of the inexperienced ratsin an unfamiliar environment.


. Cows raised in Gila county Arizonaand moved 100 miles east toApache county suffered severelupine and locoweed poisoning.Sister cows that remained in Gilacounty did not experience lupine orlocoweed poisoning even thoughthese species were available insmall to moderate stands.

SOCIAL FACILITATION

Animals can also influence what oneanother eat.

. A group of heifers that wereaverted to larkspur (with LiCl)avoided the plant over a 3-yearperiod until they were placed in apasture with nonaverted heifers, atwhich point they began eatinglarkspur at similar levels to thenonaverted heifers.

SUBTLE MOLECULAR CHANGESINCREASE PLANT TOXICITY

Animals may be unable to readilydetect subtle molecular changes thatincrease plant toxicity.

. Lambs were unable to detect thatLiCl had been added to a previ-ously “safe” familiar food (barley)when it was fed in combination witha novel food (milo). The lambsinstead avoided milo and continuedto eat the familiar barley, eventhough barley actually containedthe toxin.

. Cattle typically increase intake oflarkspur (D. barbeyi) after a drop inbarometric pressure and mortalityincreases, probably becausechanges in plant chemistry simulta-neously increase both the palatabilityand toxicity of the plant. Suchchanges likely increase susceptibilityto poisoning.

. Bitterbrush (Purshia tridentata) ismore palatable than blackbrushboth for goats and snowshoe

hares, even though both shrubscontain condensed tannins. Slightchemical differences rendercondensed tannins in blackbrushmore aversive to herbivores.

TOXINS IN MORE THAN ONE PLANT

It may be difficult for herbivores toassociate toxicity with a specific foodwhen the same toxin exists in morethan one food, or when two or morecompounds in different foods interact tocause toxicity.

. Goats and deer ingest manydifferent browse species that arehigh in tannins. It may be difficultfor them to distinguish PIF amongseveral different plant species thatcontain the same (or nearly thesame) compound.

. Sheep that consume hemlock(Cicuta spp.) may then be moresusceptible to compounds in crownbeard (Verbesina enceliodes).

. Sheep that consume black sage-brush (Artemesia nova) beforehorsebrush (Tetradymia glabrata)are predisposed to photosensitiza-tion. Photosensitization by itself isnot likely to cause a food aversionbecause the emetic system is notdirectly stimulated, but liver dys-function associated with ingestingthese two plant species mightindirectly stimulate the emeticsystem and ultimately cause aconditioned food aversion.

. Various locoweed species containtoxic nitrogen compounds andselenium, which when combinedincreases their toxicity.

SUMMARY

Animals continually sample andevaluate the nutritional value (i.e., PIF)of forages using their senses of taste,smell, and sight. Postingestive feed-


back adjusts a forage’s hedonic value(i.e., preference and palatability)commensurate with its utility to theanimal (i.e., animal age, morphology,and physiology) enabling survival whenboth the animal’s foraging environmentand nutritional needs are constantlychanging. Plant species that causepositive hedonic shifts are usuallyhighly correlated with nutritional well-being, while plant species that causenegative hedonic shifts are typicallyhighly correlated with nutrient deficien-cies and toxicosis. Hence, what makesa forage taste “good or bad” (and thus,sought or avoided) is not taste per se,but rather nutritional benefits or deficitsreceived from forage ingestion, whichare sensed by animals through PIF andlinked with a forage’s taste. Animalsintegrate and use their senses of taste,smell, and sight to seek foods thatcause positive PIF (i.e., nutritional well-being) and avoid foods that causenegative PIF (i.e., nutrient deficienciesand toxicosis), and can thus be de-scribed as possessing a high degree of“nutritional wisdom.” This processoccasionally breaks down whenanimals fail to properly link the PIF of aparticular food with its taste, smell, orsight, and their physiological means forbinding, metabolizing, or detoxifyingtoxic compounds is exceeded.

ACKNOWLEDGMENTS

We thank Roger Banner, Mick Holder,Robert Kattnig, and Jim Sprinkle forreviewing earlier drafts of this paper.Their comments and suggestionsgreatly improved the manuscript.

LITERATURE CITED

Provenza, F.D. “Feeding Behavior ofHerbivores in Response to PlantToxins.” Handbook of Plant andFungal Toxicants. J.P. Felix D’Mello, ed. CRC Press, Inc. 1997.

Provenza, F.D. “Acquired Aversionsas the Basis for Varied Dietsof Ruminants Foraging onRangelands.” J. Anim. Sci.74(1996):2010–2020.

Provenza, F.D. “Postingestive Feed-back as an Elemental Determinantof Food Preference and Intake inRuminants.” J. Range Manage.48(1995):2–17.

Provenza, F.D., J.A. Pfister, and C.D.Cheney. “Mechanisms of Learningin Diet Selection with Reference toPhytotoxicosis in Herbivores.” J.Range Manage. 45(1992):36–45.

1Associate Professor and RangelandSpecialist, The University of Arizona

2Professor, Range Science Department,Utah State University, Logan, UT

3Professor and Rangeland SpecialistThe University of Arizona

4Figures 1-3 were originally published insimilar form in the Journal of RangeManagement. They are reproduced hereby permission of the Journal.


FROM:

Arizona Ranchers’ Management GuideRussell Tronstad, George Ruyle, and Jim Sprinkle, Editors.Arizona Cooperative Extension

DisclaimerDisclaimerDisclaimerDisclaimerDisclaimer

Neither the issuing individual, originating unit, Arizona Cooperative Extension, nor the ArizonaBoard of Regents warrant or guarantee the use or results of this publication issued by ArizonaCooperative Extension and its cooperating Departments and Offices.


Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, incooperation with the U.S. Department of Agriculture, James Christenson, Director, CooperativeExtension, College of Agriculture and Life Sciences, The University of Arizona.

The University of Arizona College of Agriculture and Life Sciences is an Equal Opportunityemployer authorized to provide research, educational information, and other services only toindividuals and institutions that function without regard to sex, race, religion, color, national origin,age, Vietnam Era Veteran’s status, or handicapping conditions.


INTRODUCTION

In any supplementation program, it isessential that forage resources bestocked such that there is adequateforage quantity available per animalunit. If forage quantity is insufficient,then the supplementation program willbe ineffective. The object of supple-mentation programs (usually proteinsupplements) is to make-up deficien-cies in forage quality to increasepassage rate of forage and thusincrease forage intake of the cow.

Forage intake of the cow declines withdecreased forage quality. Cellulosecontent in mature forage increasesand requires increased rumen resi-dence time for rumen microbes tobreak down chemical bonds. Also,protein content of mature foragedecreases, allowing less protein to beavailable for making new rumenmicrobes. The net effect is for thepassage rate of forage and forageintake to decline (Table 1).

A general rule is for daily proteinsupplementation to be limited toaround 2 lbs. a day in order to avoidforage substitution effects. If energysupplements are fed, then it is gener-ally expected that negative foragesubstitution effects will occur.

COW NUTRITIONALREQUIREMENTS

An animal unit day (AUD) is defined as26 lbs. of forage per day for a 1000 lb.cow and her calf. If the forage is notgreen and actively growing, protein,phosphorus, and sometimes energy

content of the forage may be deficient.In order to meet the dietary proteinrequirements of the cow herd, theforage needs to contain 7% protein or1.6 lbs. per day for a nonlactating and9.6% or 2.0 lbs. per day for a 1000 lb.lactating cow milking 10 lbs. a day.Calcium and phosphorus requirementsfor a nonlactating 1000 lb. cow in thelast trimester of pregnancy are .26%calcium or .81 oz. per day and .20%phosphorus or .63 oz. per day. For alactating 1000 lb. cow, .28% calcium or.88 oz. per day and .22% phosphorusor .70 oz. per day are required.

As mentioned above, protein require-ments increase with lactation. For earlylactation (18 lbs. of milk), proteinrequirements are 2.14 to 2.24 lbs for a1000 lb. cow. For late lactation (7 lbs.of milk), protein requirements are 1.8 to1.9 lbs. for a 1000 lb. cow. Proteinrequirements are lowest for non-lactating cattle during mid-pregnancy,or only 1.4 lbs.

egaroFroytilibitsegiD roytilibitsegiD roytilibitsegiD roytilibitsegiD roytilibitsegiD

%NDT %NDT %NDT %NDT %NDT

deriuqeRtnuomAteeMottaEot teeMottaEot teeMottaEot teeMottaEot teeMottaEot

ecnanetniaM ecnanetniaM ecnanetniaM ecnanetniaM ecnanetniaM%,stnemeriuqeR %,stnemeriuqeR %,stnemeriuqeR %,stnemeriuqeR %,stnemeriuqeRthgieWydoBfo thgieWydoBfo thgieWydoBfo thgieWydoBfo thgieWydoBfo b

tataEnaCtnuomAegaroFeht egaroFeht egaroFeht egaroFeht egaroFeht

,detsiLytilibitsegiD ,detsiLytilibitsegiD ,detsiLytilibitsegiD ,detsiLytilibitsegiD ,detsiLytilibitsegiDthgieWydoBfo% thgieWydoBfo% thgieWydoBfo% thgieWydoBfo% thgieWydoBfo% c

34 2.3 3.1ot2.1

54 1.3 0.2ot7.1

05 8.2 1.2ot9.1

55 6.2 1.2ot7.1

85 4.2 5.2ot9.1

06 3.2 5.2ot0.2

26 3.2 8.2ot3.2

46 2.2 2.3ot6.2

46nehtretaerG 2.3ot6.2

Table 1. Forage Intake of Lactating Cattle at DifferentForage Digestibilitiesa

aFor a 1000 lb. cow milking 10 lbs. / day.bThe point of intersect for mainintenance requirements and what the animalcan eat is around 56% digestibility for lactating animals and about 52%digestibility for nonlactating animals.cResearch from various sources including Kronberg et al., 1986. J. RangeManage. 39:421; Wagner et al., 1986. J. Anim. Sci. 63:1484; Havstad andDoornbos, 1987. Proc. West. Sec. Amer. Soc. Anim Sci. p. 9; Sprinkle, 1992.M.S. Thesis, Montana State University.

MATCHING FORAGERESOURCES WITH COW

HERD SUPPLEMENTATION

Jim Sprinkle1


Human energy needs are specified incalories. Human calories are actuallyequal to 1000 calories, so an averagemale diet of 3000 calories per day isequal to 3,000,000 calories. Sincecattle are much larger than humans,energy needs for cattle are listed inmegacalories of metabolizable energy.A megacalorie (Mcal) is equal to1,000,000 calories. Metabolizableenergy (ME) is that amount of energy infeed or forage thatis available to bemetabolized or used by the body formaintenance, production, work, andheat regulation. The energy require-ment for a 1000 lb. nonlactating cow is18,000,000 calories or 18 Mcal of MEper day. To maintain a 1000 lb. rangecow milking 10 lbs. per day requiresapproximately 23,000,000 calories or23 Mcal of ME per day. Energy require-ments for cows with greater milkproduction are increased by .48 Mcal ofME per lb. of milk (1 gallon of milk =8.62 lbs.). Table 2 lists maintenancerequirements for different sizes ofcattle.

Energy is used to produce milk withabout the same efficiency as energy isused to maintain essential body func-tions. Energy for body weight gain isused less efficiently than energy formilk production with a greater portion ofthe metabolizable energy being lost asheat as body tissue is formed. Poorquality forages promote very little bodyweight gains while the energy densityof grain for body weight gain can be upto 7 times greater than that of inferiorquality forage. Because of the variabilityin available energy for body weight gainamong different feedstuffs and theaccompanying inefficiency of gain, adifferent system of specifying energyrequirements for gain (net energy forgain or NE

g) is recommended by the

National Research Council. Net energyfor gain or NE

g in a particular feed or

forage is always less than ME (seeTable 3). Table 3 lists ME and NE

g

values for known digestiblities or totaldigestible nutrients (TDN) of forages orfeeds.

.sbl,thgiewwoC,deriuqernietorPgnitatcalnon,.sbl gnitatcalnon,.sbl gnitatcalnon,.sbl gnitatcalnon,.sbl gnitatcalnon,.sbl

wocegnar wocegnar wocegnar wocegnar wocegnar

EMfolacM,deriuqer ,deriuqer ,deriuqer ,deriuqer ,deriuqer

egnargnitatcalnon egnargnitatcalnon egnargnitatcalnon egnargnitatcalnon egnargnitatcalnonwoc woc woc woc woc a

008 4.1 1.51

009 5.1 5.61

0001 6.1 0.81

0011 6.1 2.91

0021 7.1 5.02

0031 8.1 8.12

0041 9.1 0.32

0051 0.2 2.42

0061 1.2 4.52

0071 2.2 6.62

0081 3.2 8.72

evobaehtotddA:noitcudorpklimrofstnemeriuqerlanoitiddA.gnitatcalsiwocfistnemeriuqerecnanetniam .gnitatcalsiwocfistnemeriuqerecnanetniam .gnitatcalsiwocfistnemeriuqerecnanetniam .gnitatcalsiwocfistnemeriuqerecnanetniam .gnitatcalsiwocfistnemeriuqerecnanetniam

fo.sbldetamitsEyad/noitcudorpklim yad/noitcudorpklim yad/noitcudorpklim yad/noitcudorpklim yad/noitcudorpklim

fo.sbllanoitiddAyad/deriuqernietorp yad/deriuqernietorp yad/deriuqernietorp yad/deriuqernietorp yad/deriuqernietorp

EMfolacMklimrofderiuqer klimrofderiuqer klimrofderiuqer klimrofderiuqer klimrofderiuqer

5 51. 4.2

8 42. 8.3

01001;noitatcaletal(

)eromrosyad

03. 8.4

21 63. 8.5

41 24. 7.6

61 84. 7.7

81ot06;noitatcalkaep(feebtsom;syad07

)sdeerb

45. 6.8

02 06. 6.9

22;noitatcalkaep(folacipyteromsahcussdeerb

)latnemmiS

66. 6.01

aME = metabolizable energy; Mcal = megacalories (1,000,000calories). Increase maintenance requirements by 10% if Charolais,Simmental, or other large framed breed crosses; increase by 15% fordairy crosses; reduce by 10% for Brahman crosses. If daytimetemperatures exceed 95˚ F, increase maintenance requirements25%.

Table 2. Maintenance Requirements for RangeCattle


TDN = Total Digestible Nutrients; ME = metabolizable energy; NEg =

net energy for gain; Mcal = megacalories or 1,000,000 calories.

The energy costs of NEg required for

body weight gain has been determinedby research. Energy costs are depen-dent upon fat content of the gain, butfor most range cows, each 1 lb. of liveweight gain requires approximately 2.1Mcal of NE

g. Live weight gain can only

occur after the cow’s maintenance andlactation requirements are met. If a1000 lb. lactating cow milking 10 lbs.per day consumed 24 lbs. of foragewith a digestibility of 60%, then 23.5lbs. of the forage would satisfy hermaintenance requirements of 23 Mcal(see calculation below).

23 Mcal ME required per day formaintenance and lactation

÷ .98 Mcal ME = 23.5 lbs. forage lb. forage

This would leave .5 lbs. of forage forgain, which would supply .17 Mcal ofNE

g. The cow should be able to gain

.08 lbs. per day with this level of milkproduction and forage quality.

.5 lbs. of forage remaining

• .34 Mcal NEg

= .17 Mcal NEg lb. of forage

.17 Mcal NEg ÷ 2.1 Mcal NE

g

lb. of gain

= .08 lbs. average daily gain

COW HERD ASSESSMENT

The easiest way to monitor cattle is touse the body condition scoring systemdisplayed in Table 4. Briefly, if thetransverse processes of the lumbarvertebrae (between hip bones [hooks]and the ribs) are readily visible, the cowis probably a body condition score(BCS) of 3 and may not rebreed.Research has shown that reproductionwill suffer when cows have a bodycondition score less than 4. Each 1 unitincrease in body condition is approxi-mately 80 pounds, so to increase a cow

from a BCS of 3 to 4 would require alive weight gain of 80 lbs. Before a cowcan gain weight, maintenance andlactation energy requirements must bemet. It is practically impossible and verycostly for cows to gain weight duringearly lactation. Most cows will mobilizefat to support milk production for thefirst 40 to 60 days of lactation. A goodmanagement practice is to monitorbody condition 3 months before calvingand supplement accordingly to maintaindesired body condition. If possible,cattle should be at a BCS of 5 orgreater at calving to allow for weightloss during the first 60 days of lactation.Young growing cattle that will beproducing their first calf at calving, largeframe size cows, and cows with greatermilk production potential are all at riskfor becoming thin and failing to rebreed.If the grazing management plan willallow it, young or thin cattle should beseparated from the rest of the herd intoa different pasture and supplementedas necessary to maintain body condition

sisaBrettaMyrD

ytilibitsegiD deeffo.bl/EMlacMegarofro

ENlacMg

deeffo.bl/egarofro

04 66. 40.

24 96. 70.

44 27. 01.

64 57. 31.

84 97. 61.

05 28. 91.

25 58. 22.

45 88. 52.

65 29. 82.

85 59. 13.

06 89. 43.

26 20.1 73.

46 50.1 04.

Table 3. Energy Content of Forages or Feeds atDifferent Digestibilities


Table 4. System of Body Condition Scoring (BCS) for Beef Cattle

puorG SCB noitpircseD

noitidnoCnihT

1 tafelbaplaponhtiwdetaicameylemertxesiwoC-DETAICAMEsenobpih,sessecorpesrevsnart,sessecorpsuonipsrevoelbatceted

odsa,yltnenimorpetiuqtcejorpsbirdnadaeh-liaT.sbirros'llessuR.M.CekilskooL.snipdna,enobkcab,skooh,sredluohs

".0005ehtfotsaL"ro"koonihCarofgnitiaW"

2 dnadaeh-liattub,detaicametahwemossraeppallitswoC-ROOPdnaelbisiverasessecorpsuonipslaudividnI.tnenimorpsselerasbir

emostub,hcuotehtotprahsrehtarllitseradnadenifedylprahssuonipsneewtebsecapS.enipsehtgnolastsixerevoceussit

.elbisiverasessecorp

3 otprahssaetiuqtontubelbaifitnediyllaudividnillitserasbiR-NIHT-liatrevodnaenipsgnolatafelbaplapsuoivbosierehT.hcuotehtdna,sessecorpesrevsnart,sbirrevorevoceussitemoshtiwdaeh

.ecnaraeppaniprahsostontubelbisivllitssienobkcaB.senobpih)sbirdnaskoohneewteb(earbetrevrabmulfosessecorpesrevsnarT

tondnaecnaraeppaniralugnaerasretrauqdniH.elbisivylidaerera.yhself

noitidnoCenilredroB

4 .suoivboyllausivregnolonerasbirlaudividnI-ENILREDROBehT.era)sbirtsal(sbirht31dnaht21tub,elbisivtonerasbireroFtub,noitaplapnoyllaudividnideifitnediebnacsessecorpsuonips

esrevsnart,sbirrevorevoctafemoS.prahsnahtrehtardednuorleefregnolonerasessecorpesrevsnarT.senobpihdna,sessecorpotelbissopllitssititub,tafemoshtiwderevocsienipS.suoivbo

nignilcsum,thgiartstub,lluF.earbetrevlaudividnitceted.sretrauqdnih

noitidnoCetaredoMmumitpO

5 nopU.ecnaraeppallarevodoogyllarenegsahwoC-ETAREDOMedisrehtienosaeradnaygnopssleefsbirrevorevoctaf,noitaplap

tonsbirht31dnaht21ehT.revoctafelbaplapevahwondaeh-liatfofoedishcaenosaerA.knurhsneebsahlaminaehtsselnuelbisiv

.dednuomtoneratub,tafhtiwllifotgninnigeberadaehliat

6 leefotdeilppaebotsdeenwonerusserpmriF-ETAREDOMHGIHdnasbirrevoelbaplapsitaffoeergedhgihA.sessecorpsuonipspmulperasretrauqdniH.dednuorsraeppakcaB.daeh-liatdnuora

fosdnuomllamsdnasbirerofrevossenignopselbaecitoN.llufdna.daehliatedisebraeppaotgninnigeberataf

7 .tafelbaredisnocseirracylsuoivbodnayhselfsraeppawoC-DOOG,tcafnI.daeh-liatdnuoradnasbirrevorevoctafygnopsyreV

.suoivboebotgninnigeb"seldnahevol"ro"senop"ro"sdnuor"derevocsienipS.llufsiteksirB.hctorcnidnaavluvdnuoratafemoS

kcaB.dehsiugnitsidebylerabnacsessecorpsuonipsdnatafhtiw.ecnaraeppaerauqsasah

noitidnoCtaF

8 sessecorpsuonipS.denoitidnoc-revodnayhselfyrevwoC-TAF,sbirrevostisopedtafegralsahwoC.etaplapotelbissopmitsomla

.suoivboera"senop"ro"sdnuoR".avluvwolebdna,daeh-liatdnuora.teksirbllufyreV

9 dnayhctapdnaytsawylemertxeylsuoivbowoC-TAFYLEMERTXE"sdnuor"dnaeussityttafnideirubspihdnadaeh-liaT.ykcolbskool

dnaelbisivregnolonerutcurtsenoB.gnidurtorperataffo"senop"roegralybderiapmiebneveyamytilitoms'laminA.elbaplapylerab

.tafreddufostisopedyvaeH.stisopedyttaf

Adapted from Richards et al., 1986; Journal of Animal Science Vol. 62:300.


at a score of 4 or greater prior tocalving. Many producers also breedheifers to calve 30 days before the cowherd to allow them additional time torecover from the stresses of lactationprior to rebreeding. A producer shouldconsider implementing a supplemen-tation program if the forage is suchthat cattle are consistently at lessthan a BCS of 4 at breeding andconception rates are 10 to 15% lowerthan desired.

EXAMPLE OF COST OF BODYWEIGHT GAIN BEFORE CALVING

It is determined that several cattle are ata body condition score of 3, ninety daysbefore calving. The grazing manage-ment plan does not allow separation ofthin cattle into a separate pasture. Thepermittee desires to evaluate theeconomics of supplementing all 100cattle. To increase body weight 80 lbs.(1 condition score) over 90 daysrequires an average daily gain of .88lbs. It is assumed that at 55%digestibility, the forage is currentlymeeting maintenance requirements ifcattle have daily forage intakes equal to2% of their body weight. The NE

g

content of the cottonseed meal supple-ment to be fed is .50 Mcal of NE

g per lb.

If cottonseed meal was $180 per tonand 90% dry matter (DM), to gain .88lbs. per day would require feeding 4.11lbs. of protein supplement per day at acost of $0.37 a day.

.88 lbs gain • 2.1 Mcal NEg

day lb. gain

= 1.85 Mcal NEg required

day

1.85 Mcal NEg ÷ .50 Mcal NE

g

day lb. cottonseed meal

= 3.7 lbs DM cottonseed meal

3.7 lbs. DM cottonseed meal

÷ .90 dry matter lb. as fed cottonseed meal

= 4.11 lbs. as fed cottonseed meal

• $0.09 = $ .37 per day lb.

The 90 day cost per cow would be$33.30, or $3330 for 100 cows. Ifconception rates increased only 10%by increasing body condition by 1 unit,the value added for calves would be$3000 if calves weighed 400 lbs. atweaning and sold for $0.75 per lb. Iflabor is factored in at $20 per day tofeed the supplement and supplementwas fed three times per week (9.59 lbs.per cow per feeding), net loss would be$930.

[$3330 supplement cost + $600 laborand gas (3 times/ week feeding)] -($3000 value from calves) = $930 loss

In order to break even on the cost ofsupplement + labor and gas in theabove scenario, two-thirds of the cowherd would need to be at a bodycondition of 3.

$3930 total cost of supplementation ÷$300 per calf = 13.1 calves

13.1 calves ÷ 20% conservativeestimate of increased conception withcow BCS of 4 vs. 3 during breeding= 65.5 cows

It is much more cost effective toseparate thin cows from fat cows 3 to 4months before calving, and to supplementthem to be at a BCS of 5 or greater atcalving. Ideally, cattle should go intowinter with a BCS of 5 or greater. Thisallows for a cushion for weight losswhen forage quality and availabilitydecline. Thin cows, especially first calfheifers, could possibly benefit fromweaning calves 1 or 2 months early totake advantage of lower cow mainte-nance requirements and the opportu-nity for gain before forage quality andavailability drop in late fall. If first calfheifers have calved two weeks to amonth before the cow herd, this canoffset some of the reduced weaning


weight. Also, late summer calf pricesare often slightly higher than autumncalf prices. Producers can benefit byevaluating forage as described below inorder to match cow nutritional require-ments to forage quality. This will allowfor forward planning of weight loss in thecow herd and enable designing a costeffective supplementation program.

FORAGE ASSESSMENT

Forage Quality. In order to match cowrequirements to the available forage,lab analyses of forage samplesrepresentative of the cow herd diet areencouraged. By matching cow nutritionalrequirements with forage contributions,a cost effective supplement programcan be developed. When forage isgreen and actively growing, foragequality should be sufficient to meet acow’s nutritional requirements. Asforage matures, forage quality isreduced substantially. At a minimum,the forage should be analyzed forprotein and TDN, and, if possible, calciumand phosphorus. Local CooperativeExtension offices can furnish addressesand phone numbers of laboratorieswhich can provide this service.

Another option to plant testing is toanalyze fecal samples from a crosssection of the herd (approximately 10cows) using a new technique callednear infrared spectroscopy (NIRS). Thistechnique uses reflected infrared lightto estimate digestibility, protein, andphosphorus content of the forage diet.Unless the cow’s diet contains 30% orgreater brush content, NIRS can be arapid and easy method to determinenutrient content of the diet. Currently,Texas A & M University (Department ofRangeland Ecology and Management,Grazingland Animal Nutrition Lab,College Station, TX 77843-2126) isdoing this procedure. The phonenumber for more information is(409) 845-5838.

Currently, the cost for protein and TDNplant analyses is approximately $18,

and the cost for NIRS is around $24with shipping costs included. The NIRSprocedure may more accuratelyestimate energy and protein content ofthe selected diet, but is not recom-mended when diets consist of largequantities of brush. If plant analysis ispracticed, it is important to select arepresentative sample similar to whatthe cows are actually eating by plantspecies and percentage.

Benefits are not usually realized innonlactating cattle for protein supple-mentation unless the forage has lessthan 6.25% protein. Protein supplemen-tation when protein content of theforage is below this level will increasemicrobial synthesis of protein in therumen and also increase passage rateand intake of poor quality forage. Ifforage has less than .28% calcium and.22% phosphorus as a percentage ofdry matter, then lactating cattle (1000lbs.) should have a free choice calciumand phosphorus mineral mix providedin addition to trace mineral salt. TheTDN or digestibility content of theforage for lactating cattle is marginal ataround 56%. For nonlactating cattle,TDN is marginal at around 52%. Asdigestibility of the forage drops, resi-dence time in the rumen increases andforage intake decreases to levelsinadequate to maintain production andreproductive success.

Additional Considerations for ForageQuality. Let us assume a cow herdconsists of 1200 lb. cows milking 16lbs. per day and that forage quantity isno problem. The cows' maintenanceand lactation energy requirementswould be equal to 20.5 + 7.7 Mcal or28.2 Mcal of ME per day (Table 2). Ifthe forage digestibility is 60% (greenand actively growing), then the energyconcentration for maintenance wouldbe .98 Mcal of ME per lb. of forage(Table 3). This would equal 29 lbs. offorage per day that needs to be eatento maintain body weight, or 2.4% ofbody weight. This level of intake ispossible with forage quality this good. If


forage quality dropped to 54% digest-ibility, then forage intake would need tobe 2.7% of body weight, which isprobably not possible with forage of thisquality. In this instance, the cow wouldneed to reduce milk production or losebody weight, or both. If the cow had abody condition score of 6, then weightloss would probably not be a problem.However, if the cow had a body condi-tion score of 4, then potential problemscould exist for rebreeding.

Because minimal cheap harvestedfeed or crop aftermath exists in Arizona,it is probably advantageous to matchyearly forage resources to the calvingseason to reduce supplementalfeeding. If a sufficient quantity ofnutritious green spring forage isavailable, then traditional springcalving is practical. On the other hand,if forage quantity is limiting and oftenof poor quality during early spring,then it may be advantageous to movethe calving season forward to synchro-nize with summer monsoon rains.Nonlactating cattle will consume about30% less forage than lactating cattleand forage quality of dormant foragewill more closely match nutrientrequirements for nonlactating cattle.

SUPPLEMENTATION DECISIONS

Once the cow requirements are definedand forage quality determined, adecision can be made to supplementprotein or energy or both. Usually, thebest practice is to satisfy proteinrequirements first. This gives the bestchance for increasing forage intake andincreasing energy intake. After proteinrequirements are met, additionalprotein and energy may need to besupplemented in order to meet energyrequirements or for weight gain. If theallotment is accessible, supplementa-tion may have positive economicbenefits in subsequent calving percent-ages. Supplemented cattle should bemonitored frequently for body conditionto evaluate the success of the supple-mentation program.

Energy Supplementation. If the energycontent of the forage is deficient,supplementation of energy will decreaseforage intake and possibly foragedigestibility. This may sometimes be anadvantage in stretching forage supplies.Some of the negative forage substitutioneffects of energy supplementation uponforage intake can be overcome byincluding greater proportions of feedbyproducts high in fiber such as corngluten feed in the energy supplement.Energy supplements also have thedisadvantage of needing to be supple-mented at least every other day, andpreferably every day. This may beimpractical for many range operations.Boss cows may overload with energywhen supplemented at less frequentintervals. Salt-limited supplements arealso an option, but oftentimes costdiscounts are not applied to the com-mercial supplement for the 20% saltincluded. Another solution may be tofeed molasses based blocks, but aneconomic analysis should be conductedto determine costs and benefits of thistype of energy supplement.

Protein Supplementation. Due to itspositive effects upon forage intake,protein supplementation is the mostfrequently practiced of all supplemen-tation regimes. Research in west Texashas shown that cattle may be effec-tively supplemented with protein asinfrequently as once a week (seventimes daily rate of supplementation of 2lbs. per day). As mentioned earlier,protein supplementation may increaseforage intake, allowing for greaterintake of nutrients. Since proteinsupplements are costly, forage evalua-tion is recommended to determine ifprotein supplementation is necessary.For nonlactating cattle, the forageshould contain less than 6.25% protein.Lactating cattle may benefit fromprotein supplementation if forage isbelow their requirements (9.6% for1000 lb. cow), but they should be ableto tolerate a slight deficiency since theycan select a diet higher in protein thanrandom pasture clippings. If forage


availability is inadequate, proteinsupplementation may be inefficient. Ifforage utilization in a pasture is alreadyat 50%, then don’t expect proteinsupplementation to enhance forageintake. Managers who use proteinsupplementation effectively withdormant forages often do so by estab-lishing ungrazed forage “banks” orpastures to use in conjunction withprotein supplementation. By doing so,the manager ensures adequate forageavailability. If forage availability isinadequate, feeding larger quantities ofa protein-energy supplement would bea better choice to attempt to minimizeweight loss.

Bypass Protein Supplementation. If thecow herd has been experiencingpronounced loss of body condition andthe energy content of the forage isadequate, supplementation with aruminally undegradeable proteinsupplement or bypass protein may beadvantageous. Research in Montanaon dormant winter range has shownthat the feeding of bypass proteinsupplements may reduce weight loss instressed cows. Also, earlier estrusactivity following calving may exist incows fed bypass protein. Feedstuffshigh in bypass protein include feathermeal, blood meal, corn gluten meal,and fish meal. Due to palatabilityproblems, rendered animal productsare usually limited to 25 to 30% of thetotal supplement and are combinedwith grain products to increase palat-ability. The effectiveness of bypass

protein is influenced by the type offorage. For instance, research in Texasreported that cottonseed meal contains50% bypass protein when fed with coolseason forages, but only 23% withwarm season forages. The disadvan-tage with feeding bypass protein iscost. Bypass protein supplements maycost twice as much as normal proteinsupplements.

Supplement of Indecision. Sometimesa producer is unsure whether tosupplement protein or energy. Usually,when forages are low in energy, theyare also low in protein. Cool seasonforages tend to have greater digestibil-ity than warm season grasses. DormantTobosa grass can be very low in bothdigestibility and protein. The “supple-ment of indecision” combines bothprotein and energy. An examplesupplement would contain 40% naturalprotein, 50% grain products, tracemineral salt, vitamins A and D,dicalcium phosphate, and potassiumchloride. Fed at a rate of 2 pounds aday the 90 days preceding calving,there would probably be a slightdecrease in BCS if the forage was lowin protein and forage availability wasadequate.

EXAMPLE CASE STUDIES OFSUPPLEMENTATION

As mentioned previously, supplemen-tation of cattle should occur beforecalving. Minimal results will beachieved through supplementation thefirst 45 to 60 days after calving, andattempting to restore body conditionafter this time will be twice as costly assupplementing for weight gains beforecalving.

Two examples are presented at the endof this section: I. Maintaining a cow at aBCS of 5, ninety days before calvingwhen forage quality is inadequate; and,II. Increasing BCS from 4 to 5, seventydays before calving when forage qualityis adequate.

sisaBrettaMyrD

ffutsdeeF nietorP%/lacM,EM

.bl a

ENg

/lacM,.bl a

nroC 0.01 94.1 76.

oliM 4.21 03.1 85.

laeMdeesnottoC 8.44 32.1 05.

moolblluf,yaHaflaflA 9.51 58. 22.

aME = metabolizable energy; Mcal = megacalories (1,000,000calories); NE

g = net energy for gain.

Table 5. Protein and Energy Content of SomeSupplements


Table 5 provides nutrient content of somefeedstuffs. Other values can be obtainedfrom National Research Council tablesfor feedstuffs or from your feed company.Least cost computer programs are alsoavailable to calculate the least expensivesupplements to feed.

SUMMARY

Ideally, body condition of cattle shouldbe 5 or greater for maximum reprod-uctive success. If BCS drops below ascore of 4 at breeding, calvingpercentages will decrease sharply.

Producers should manage their herdsthrough supplementation regimes toobtain at least a BCS of 5 at calving.The least costly and most effectivetime to supplement is before calving. Ifcattle are still thin at calving, theyshould be placed on a higher plane ofnutrition at least 60 to 90 days toincrease conception rates. This maybe accomplished with higher qualitypastures if available or supplementationor both. Forage which is not green andactively growing should be analyzed todetermine what type of supplemen-tation to practice and at what level.

1Area Extension Agent, Animal ScienceUniversity of Arizona


1. Determine Forage Quality.Forage digestibility is 50% and protein is 6.2%.

2. Determine Cow Maintenance Requirements (Table 2).For a 1000 lb. nonlactating cow in the last trimester of pregnancy, 18 Mcal of ME and 1.6 lbs.protein are required.

3. Estimate Forage Intake (Table 1).Forage intake is estimated at 1.8% of body weight (a little less since cow is nonlactating).

4. Determine if Maintenance Requirements are Being Met.Protein: 18 lbs. forage intake • .062 protein in forage = 1.116 lbs. The forage is deficient inprotein by .484 lbs. (1.6 - 1.116 = .484 lbs.) Using cottonseed meal as a supplement wouldrequire 1.08 lbs. of cottonseed meal per day (Table 5, dry matter basis). (.484 ÷ .448 protein/lb. cottonseed meal = 1.08 lbs.)

Energy: 18 lbs. forage intake • .82 Mcal ME per lb. (see Table 3 to convert TDN to ME) = 14.76Mcal. The forage is deficient by 3.24 Mcal. (18 - 14.76 = 3.24 Mcal). Using cottonseed mealas supplement would require 2.63 lbs. of cottonseed meal per day (Table 5, dry matter basis).(3.24 ÷ 1.23 Mcal ME/lb. cottonseed meal = 2.63 lbs.)

So, to satisfy the maintenance requirements of this cow would require about 2.9 lbs. ofcottonseed meal per day. (Must convert dry matter to as fed basis: 2.63 ÷ .90 dry matter =2.9 lbs.)

5. Supplement for Maintenance if Necessary.To supplement this cow at this level for 90 days preceding calving would require 2.9 lbs. ofprotein supplement per day for a cost of $ .25 per day or $22.50 for 3 months ($9.00 per cwt.for cottonseed meal).

6. Determine if Body Condition is Adequate.Adequate.

7. Supplement for Weight Gain if Needed.Not needed.

8. Financial Analysis.If a 10% increase in conception occurs as a result of supplementation and calves are bornon an average 20 days earlier, then the net profit excluding labor and gas is $19.50 (400 lb.weaning weights; 1.5 lbs. average daily gain on calves).

20 days • 1.5 ADG • .60/lb. = $ 18.0010% increase in conception: 24.00(400 lbs. • .60/lb • .10)

42.00less supplement cost - 22.50profit exc. labor and gas $ 19.50

Example I. Maintaining a Cow at BCS of 5 with Inadequate Forage Quality


1. Determine Forage Quality.Forage digestibility is 55% and protein is 8.5%.

2. Determine Cow Maintenance Requirements (Table 2).For a 1000 lb. nonlactating cow in the last trimester of pregnancy, 18 Mcal of ME and 1.6 lbs.protein are required.

3. Estimate Forage Intake (Table 1).Forage intake is estimated at 2.0 % of body weight.

4. Determine if Maintenance Requirements are Being Met.Protein: 20 lbs. forage intake • .085 protein in forage = 1.7 lbs. The forage is adequate inprotein.

Energy: 20 lbs. forage intake • .90 Mcal ME per lb. (see Table 3 to convert TDN to ME) = 18Mcal. The forage is adequate in energy.

5. Supplement for Maintenance if Necessary.Not necessary.

6. Determine if Body Condition is Adequate.Inadequate. Needs to increase by 1 condition score before calving, or by 80 lbs.

7. Supplement for Weight Gain if Needed.Average daily gain needed over 70 days is 1.14 lbs. (80 lbs. ÷ 70 days = 1.14 lbs.) Thisrequires 5.3 lbs. of cottonseed meal per day (as fed basis). (1.14 lbs. ADG • 2.1 Mcal NE

g

required per lb. of gain = 2.394 Mcal NEg; 2.394 Mcal NE

g required ÷ .50 Mcal NE

g per lb. of

cottonseed meal (Table 5) = 4.788 lbs. cottonseed meal (dry matter basis); 4.788 lbs. ÷ .90dry matter = 5.3 lbs. cottonseed meal per day.

8. Financial Analysis.In this example, weight gain is expensive using a protein supplement. If a cheaper proteinsupplement could be obtained with a higher NE

g concentration per lb. of supplement, then

it would cheapen things somewhat. Also, a judgment call is required here. In most years, thesubstitution of grain products could cheapen the cost of gain by about 1/2. There may besome decline in forage intake (possibly up to 15%), but this can be alleviated somewhat byfeeding the grain supplement during the early afternoon (around 1 PM). Unless the weatheris cold, cattle should not be grazing as actively during this time period, so there will be lesssubstitution of energy obtained from the grain for energy obtained from grazing. If the proteinsupplement was fed, then the gross profit before discounting labor and gas would only be$8.50 per cow. This may be marginal in profitability. If corn were fed, 4 lbs. of corn would berequired per day to achieve the same weight gains. At a corn price of $7.50/cwt, the cost perday for corn would be around $0.25 to $0.30 per day or $17.50 to $21.00 for the feedingperiod.

For Protein Supplement For Grain Supplement20 days • 1.5 ADG • .60/lb. = $ 18.00 20 days • 1.5 ADG • .60/lb. = $ 18.0010% increase in conception: 24.00 10% increase in conception: 24.00(400 lbs. • .60/lb • .10) (400 lbs. • .60/lb • .10)

42.00 42.00less protein supplement cost - 33.60 less grain supplement cost - 21.00profit exc. labor and gas $ 8.40 profit exc. labor and gas $ 21.00

Example II. Increasing Cow Condition from 4 to 5 with Adequate Forage Quality


FROM:








INTRODUCTION

Arizona can be characterized as havinga bimodal (occurring twice a year)pattern of forage production whichaccompanies the seasonal summermonsoons and winter rains or snows.Forage quantity and quality decreaseduring the winter dormant season andthe “summer slump” preceding summerrains (Figure 1). However, foragequality during any given month can bequite variable, depending upon thetiming, frequency, and amount ofmoisture. This is illustrated in Table 1.

DETERMINING WHEN TOSUPPLEMENT PROTEIN

Generally speaking, crude proteincontent required in the forage to meetthe requirements of rumen microbesthat digest fiber is around 7%. Whencrude protein in forage is below 6.25%,forage intake for the nonlactating cowdrops sharply (Figure 2).

Providing supplemental protein whencrude protein is less than 6.25% canincrease forage intake and sometimesforage digestibility, reduce weight lossbefore calving, and ultimately increaseconception rate and profitability.

If the Total Digestible Nutrients (TDN)of forage is around 52 to 55%, forageintake required to maintain a nonlactatingcow is around 1.8 to 2.1% of bodyweight or around 18 to 20 lbs. This istrue if protein requirements are beingmet by the forage or by feeding supple-mental protein. If protein is deficient inthe diet, severe weight loss can occursince the cow must break down bodytissue to supply the necessary protein.

Table 1. Range In Crude Protein by Month

1979, 1980-81,1995-96

Blue Gamma in Arizona

Figure 1. Forage Production in Arizona

Forage Production

Jan June Aug Dec

It takes 6.7 lbs. of lean tissue to supply1 lb. of protein (Berg and Butterfield,1976). Conversely, if the diet isdeficient in energy (TDN), this onlyrequires 1 lb. of body weight loss foreach 1 lb. of TDN (NRC, 1989).

As shown in Figure 2, when foragefails to meet protein requirements ofthe microbes in the rumen, intakedecreases. This is because microbenumbers and (or) microbe activitydecrease, reducing forage digestibilityand increasing exit time from the rumenfor fiber. When the forage only contains4% crude protein, Figure 2 projectsforage intake of only 1.2% of bodyweight. Forage intake at this level wouldcause extreme weight loss. Ignoring

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PROTEINSUPPLEMENTATION

Jim Sprinkle1


deficient protein and only considering theenergy deficit, weight loss in the aboveexample could exceed 4 lbs. per day.

As a general rule, do not supplementprotein when the forage containsgreater than 6.25% crude protein(Caton et al., 1988). However, benefitswill be gained by protein supplementa-tion when crude protein in forage is low.This principle is illustrated by Tables 2and 3. In the first example (Table 2),forage intake and overall nutrient intakeincreased by 27% when steers on a 6%crude protein hay diet received addi-tional protein. In the second example(Table 3), supplementing steers grazingtobosa grass was only beneficial whenthe forage contained less than 7%crude protein.

Obviously, the only way to decide ifyou need to supplement crude proteinor not is to test forage for proteincontent. Your local Extension office canprovide a list of commercial labs whichperform this service. The cost for crudeprotein and TDN analyses totals around$18. Alternatively, near infraredspectroscopy (NIRS) analyses can beperformed on fecal samples providedthe cow’s diet does not exceed 30%brush. This service is provided byTexas A & M University GrazinglandAnimal Nutrition Lab at College Station,TX (phone 409-845-5838).

It should be mentioned that proteinsupplementation is only effective whenan adequate quantity of forage isavailable. The strategy with supple-menting protein is to feed the microbesenough protein to enable the cow tomore effectively process and harvestcheap, low quality forage. When forageutilization (removal of available quantityby livestock, wildlife, and insects)exceeds 50% of the total mass,protein supplementation may beineffective and expensive. In thisscenario, it would be more advantageousto feed a combination protein/energysupplement. The next two graphssupport this point. In the first graph,

Table 3. Protein Supplementation with Cottonseed Meal

Steers Grazing Tobosa

Adapted from Pitts et al., 1992: Journal Range Mgmt. 45:226-231

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5.1 71.0 75.1 41.0 70.0-

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5.1 71.0 63.2 02.0 30.0-

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Table 2.Cottonseed Meal Supplementation

Steers Fed 6% Crude Protein in Prairie Hay

McCollum and Galyean, 1985 Journal Anim. Sci. 60:570–577.

Figure 2. Effect of Crude Protein on Forage Intake

Nonlactating Cow on Native Range

Adapted from: Cochran, 1995 KSU Range Field Day.

Crude Protein

Forage Intake, % of Body Weight


(Figure 3) researchers found thatmaximum animal gain per acre wasachieved when forage utilization was40 to 50%. Animal performancedropped sharply when forage utilizationreached the 60% level. The standardrule of range management for planthealth is “to take half and leave half.”This is also good animal management.In the second graph (Figure 4), anexperiment was conducted with proteinsupplementation on mid-grass prairie attwo different stocking rates. In the heavystocking rate regime, protein supple-mentation was not economically sound.

The ideal time to supplement protein interms of a cow’s physiological cycle is60 to 90 days before calving. This isthe time period when maintenancerequirements are low and you receivethe biggest “bang for your buck” inpreventing weight loss and increasingconception rate. In most of Arizona withtraditional spring calving, this accompa-nies the forage winter dormancy period.It is an expensive proposition to try toput on weight after calving, as MotherNature is working against you. Thedemands of early lactation induceweight loss which is almost impossibleto reverse until after about day 45 to 60of lactation. It is a more cost effectivepractice to have the cow maintain orput on weight before calving to providea safety cushion for weight loss. Table4 illustrates the importance of havingcattle in good body condition at calving.

This research was done with two-year-old cows in LA, OK, and SC, but theresults are similar to those in otherstates. If in spite of your best efforts,cattle are thin at calving, opportunitiesmay exist to “flush” British and Conti-nental cross cattle with better qualitypastures and (or) supplements follow-ing peak lactation (around 60 to 70days). This stage of lactation wouldaccompany the forage “summer slump”time period for many Arizona ranchingoperations. If cattle have sufficient bodyfat reserves at calving they may safelycoast through the summer slump and

Figure 3. Animal Performance and Stocking RateUpland Blue Grama Range in Colorado

Adapted from: Bement, 1969 Journal of Range Mgmt. 22:83-86.

Figure 4. Effect of Stocking Rate Upon CottonseedMeal Supplementation

McCollum et al., 1992 Marvin Klemme Range Res. Sta. Report, OK

Ani

mal

Gai

n pe

r A

cre,

lbs.

Average D

aily Gain, lbs.

40% utilization

60% utilization

Ungrazed Herbage (lbs. per acre) Average Daily Gain Gain/Acre (lbs.)

Stocking Rate Treatment (1 lb. CSM/d) Control

7.5 A/Steer 5.6 A/Steer

Average Daily Gain, lbs.

Table 4. Pregnancy % by Body ConditionScore

Spitzer et al., 1995 Journal of Animal Science 73:1251–1257

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maintain acceptable conception rates.However, if cattle are below a bodycondition score of 4 at breeding time, itmay be time to consider using a proteinsupplement if forage quality is low.Unfortunately, flushing thin cattlefollowing peak lactation does not seemto work for Brahman cross cattle.Research in Australia has shown thatlactating Brahman cattle often put theenergy obtained from supplements intomilk production instead of body fat(Hunter, 1991). This would suggest thatthe only opportunity one has forincreasing fat stores for grazingBrahman cross cattle is before calving.

HOW MUCH SUPPLEMENT TO FEED

The most cost effective method infeeding protein supplements is tosupplement what is deficient in theforage (amount of protein required byanimal – amount contained in forage).Guidelines for doing this are con-tained in another article in this guideentitled, Matching Forage Resourceswith Cow Herd Supplementation. Ihave listed the maintenance require-ments for a 1000 lb. cow in Table 5,but requirements will differ for differ-ent size cows. As an example incalculating the amount of protein tosupplement, forage crude protein wastested and found to be 4%. For a1000 lb. nonlactating cow, the amountof protein which needs to be fed was2.32 lbs. per day and is calculated asfollows:1. Find the daily requirement, which is

1.6 lbs.

2. Determine the amount contained inforage. If we estimate forage intaketo increase to 1.7% of body weightfor the supplemented cow, thencrude protein in the forage is .68 lbs.(1000 x .017= 17 lbs; 17 x .04 crudeprotein in forage = .68 lbs. protein)

3. Subtract the amount contained inforage from the daily requirement,which gives .92 lbs. of protein whichneeds to be supplemented.(1.6 – .68 = .92 lbs. of protein needed)

4. Determine the amount of supplementto feed by dividing the amount ofprotein needed by the proteincontent of the supplement. If wefeed cottonseed meal (44% crudeprotein), then we need to feed 2.09lbs. of cottonseed meal on a drymatter basis. (.92 lbs. protein needed÷ .44 lbs. protein/lb. cottonseed meal= 2.09 lbs. cottonseed meal)

5. Since most protein supplementscontain about 10% water, convertfeed on a dry matter basis to an “asfed” basis. This would require thefeeding of 2.32 lbs. of cottonseedmeal per day to meet proteinrequirements. (2.09 ÷ .9 = 2.32 lbs.cottonseed meal)

The protein could be fed once a week(7 times the daily rate) without harmingthe cow (Huston et al., 1999). Ruminantanimals have an ability to recycle someof the excess nitrogen contained inprotein back into the rumen after it isconsumed the first time (Owens andZinn, 1988). Do not feed energy (highgrain, protein less than 22%) supple-ments with less than daily feeding orproblems like acidosis and foundercan occur.

WHAT KIND OF PROTEINSUPPLEMENT TO USE

The greatest benefits for proteinsupplements are usually obtained withhigh protein of a natural origin (no proteinfrom urea). These type of supplementsare also the most expensive to use. Aportion of the protein can be obtainedfrom urea in order to cheapen the

Table 5. Maintenance Requirements of Range Cattle

(1000 lb. cow)

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protein supplement. Too much urea inthe supplement can result in reducedintake of the supplement due topalatability problems or urea toxicity ifcattle consume too much of thesupplement. Recommendations forurea substitution of natural protein willbe discussed later.

It is important to know the ideal com-position of protein supplements to feed.Although we know very little concerningthe ideal amino acid profiles, researchhas identified the advantage of usingsupplements with greater crude protein.When five trials in Kansas weresummarized, researchers found thatincreasing crude protein of the supple-ment from 15 to 22 to 28% resulted in49% greater forage intake and 22%greater forage digestion (as cited inPaterson et al., 1996). Kansasresearchers also found that cattle fed a13% crude protein supplement lost 193lbs. over the winter and cattle fed a39% crude protein ration lost 97 lbs.over the winter (DelCurto et al., 1990).

In stressful situations in which cattle arelosing weight, some benefits have beendemonstrated by feeding supplementswith approximately 40 to 60% of theprotein being ruminally undegradable orbypass protein. Feedstuffs high inbypass protein include feather meal,blood meal, corn gluten meal, and fishmeal. Due to palatability problems,rendered animal products are usuallylimited to 25 to 30% of the total supple-ment and are combined with grainproducts to increase palatability.Petersen et al. (1996) reported thatweight loss has been reduced andconception rates increased in severalexperiments by feeding bypass protein.However, they reported that bypassprotein supplementation only seems to beeffective when animals are losing weight.The additional cost per ton for addingbypass protein is around $50 to $80.

When urea is substituted for naturalprotein in the supplement, it is recom-mended that no more than 30% of the

crude protein in the supplement comefrom urea (Köster et al., 1996). Table 6presents research data from Kansasshowing a slight decrease in cowperformance when the percentage ofcrude protein derived from urea was30%. If forage quality is very low and thesupply of forage limited (as in drought)avoid the feeding of any urea at all.

Liquid feed supplements can beexpected to have similar results to drysupplements. If the supplement doesnot contain sufficient protein (less than22% crude protein) it can be expectedto perform as an energy supplement.Usually, energy supplements result insubstitution of forage by the supple-ment and can decrease both forageintake and forage digestibility (Catonand Dhuyvetter, 1997). Urea is oftenadded to liquid supplements to increasecrude protein. Modern technology hasdevised an urea molecule that breaksdown more slowly than the ureamolecule used in past formulations.This has reduced the danger of ureatoxicity for liquid feeds. Assumptionsmade above for dry feeds on thepercentage of urea included in feedsand their effect upon performance areprobably valid for liquid feeds also. Thisis illustrated in Figure 5. Incrementalincreases in pregnancy rate wereachieved by increasing protein of themolasses supplement by urea and thenby cottonseed meal plus urea.

Table 6. Substitution of Urea for Natural Protein

Koster et al., 1996 KSU Cattemen's Day

Cows Grazing Winter Tallgrass Prairie

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In a presentation given to the AmericanFeed Industry Association in 1995, J.E.Moore made the following conclusionsconcerning the use of liquid feeds:

1. When forage quality was low, forageintake and average daily gain(ADG) increased, but ADG couldstill be low or negative.

2. When forage quality was high,forage intake decreased, but ADG

increased if supplement containedmeal + urea or meal.

3. Forage intake decreased if forageintake was greater than 1.75% ofbody weight.

4. Forage intake increased if forageintake was less than 1.75% of bodyweight.

5. Forage intake decreased if supple-ment intake exceeded .8% of bodyweight (about 8 lbs. for a 1000 lb.cow).

6. Forage intake increased when crudeprotein of the supplement wasgreater than 22%.

7. Liquid feeds acted similarly to drysupplements for forage intake.

DECIDING WHICHSUPPLEMENT TO BUY

The way to evaluate protein supple-ment purchases is to calculate the costof each lb. of protein dispensed.Example 1 illustrates this for onesupplement fed once a week at seventimes the daily rate vs. another supple-ment that is self fed.

In Example 1, costs are similar, so amanagement decision needs to bemade. If the producer desired to look athis herd more often, then he might optfor Supplement A. Otherwise, he maywish to use the self-fed supplement.

CONCLUSIONS

1. The purpose of protein supplemen-tation is to feed microbes so thecow can harvest more cheap forage.

2. Adequate available forage isrequired for protein supplementationto be effective.

3. Forage should be tested to deter-mine if supplementation is needed.

4. Young cows respond more favorablyto protein supplementation than doolder cows.

5. If forage is less than 6.25% crudeprotein (CP), protein supplementa-tion typically increases forageintake, decreases weight loss, andincreases conception.

Pate et al., 1990 Journal Anim. Sci. 68:618-623

Figure 5. Molasses Supplements

3-Year-Old Cows Fed Stargrass Hay (4-6% CP)

Pregnancy Rate, %

Molasses AloneMolasses + UreaMolasses + CSM + Urea

Supplement A: Fed once/wk (2 lbs./d x 7 = 14 lbs/feeding)Supplement B: Self fed (2.5 lbs/day)

1. Determine protein content of supplements:Supp. A: 44% CP x 2000 lb. = 880 lb. proteinSupp. B: 36% CP x 2000 lb. = 720 lb. protein

2. Determine the cost/lb. protein:Supp. A: $228/T or 228 ÷ 880 lb. = $ .26/lb. proteinSupp. B: $260/T or 260 ÷ 720 lb. = $ .36/lb. protein

3. Determine the cost of dispensing supplements:Supp. A: $70/T or 70 ÷ 880 = $ .08/lb. proteinSupp. B: $20/T or 20 ÷ 720 = $ .03/lb. protein

4. Determine protein each cow eats each day:Supp. A: 2 lbs. x .44 = .88 lb. proteinSupp. B: 2.5 lbs. x .36 = .90 lb. protein

5. Determine the cost/cow/day:Supp. A: .88 lbs. protein x (.26 + .08) = $ .34/daySupp. B: .90 lbs. protein x (.36 + .03) = $ .35/day

6. Determine the cost for the herd:Supp. A: $ .34 x 60 d x 100 cows = $ 2040Supp. B: $ .35 x 60 d x 100 cows = $ 2100

Example 1: Deciding Which Supplement to Buy


6. The optimum time to supplement is60 to 90 days before calving.

7. As a general rule, forage with 4%CP requires about 2 lbs. of cotton-seed meal or soybean oil meal percow per day.

8. To avoid hurting animal performance,keep CP by urea less than 30% ofthe total CP of the supplement.

9. Liquid feed functions much like dryprotein supplements.

10. It is advisable to keep CP insupplements greater than 22%with low quality forage.

LITERATURE CITED

Bement, R. E. “A Stocking Guide forBeef Production on Blue GramaRange.” J. Range Manage.22(1969):83–86.

Berg, R. T., and R. M. Butterfield. NewConcepts of Cattle Growth. SidneyUniversity Press, Australia. 1976.

Caton, J. S., A. S. Freeman, and M. L.Galyean. “Influence Of ProteinSupplementation on Forage Intake,In Situ Forage Disappearance,Ruminal Fermentation and DigestaPassage Rates in Steers GrazingDormant Blue Grama Rangeland.”J. Anim. Sci. 66(1988):2262–2271.

Caton, J. S., and D. V. Dhuyvetter.“Influence of Energy Supplemen-tation on Grazing Ruminants:Requirements and Responses.”J. Anim. Sci. 75(1997):533–542.

Cochran, R. C. “Developing OptimalSupplementation Programs forRange Livestock.” pp. 58–71. In:Fifty years of Range ResearchRevisited. KSU Range Field Day.Oct. 27, 1995. Manhattan KS.

DelCurto, T., R C. Cochran, L. R.Corah, A. A. Beharka, E. S.Vanzant, and D. E. Johnson.“Supplementation of DormantTallgrass-Prairie Forage. II. Perfor-mance and Forage Utilization

Characteristics in Grazing BeefCattle Receiving Supplements ofDifferent Protein Concentrations.”J. Anim. Sci. 68(1990):532–542.

Hunter, R. A. 1991. “Strategic Supple-mentation for Survival, Reproduc-tion and Growth of Cattle.” pp. 32–47. Proc. Grazing Livest. Nutr.Conf., August 2–3, 1991. Okla-homa State University, Stillwater.

Huston, J. E., H. Lippke, T. D. A.Forbes, J. W. Holloway, and R. V.Machen. “Effects of SupplementalFeeding Interval on Adult Cows inWestern Texas.” J. Anim. Sci.77(1999):3057–3067.

Köster, H. H., R. C. Cochran, K. C.Olson, T. J. Jones, E. S. Vanzant,and E. C. Titgemeyer. “Effect ofIncreasing Urea Level in ProteinSupplements on Pperformance byBeef Cows Consuming Low-QualityTallgrass-Prairie Forage.” pp. 46–48. Ag. Exp. Sta. Rep. of Progress756, Kansas State Univ.,Manhattan, KS. 1996.

McCollum, F. T., and M. L. Galyean.“Influence of Cottonseed MealSupplementation on VoluntaryIntake, Rumen Fermentation andRate of Passage of Prairie Hay inBeef Steers.” J. Anim. Sci.60(1985.):570–577.

McCollum, F. T., R. L. Gillen, and C.Worthington. “Performance ofSteers Grazing Rangeland atDifferent Stocking Rates andSupplemented with a High ProteinFeed.” Marvin Klemme Range Res.Sta., Field Day Rep. p. 8. Okla-homa Agric. Exp. Sta. 1992.

Moore, J. E., J. G. P. Bowman, and W.E. Kunkle. “Effects of Dry andLiquid Supplements on ForageUtilization by Cattle.” In: Proc. AFIALiquid Feed Symposium. pp. 81–95. American Feed Industry Assoc.,Arlington, VA. 1995.


NRC,. Nutrient Requirements of DairyCattle. (6th Ed.). National AcademyPress, Washington, DC. 1989.

Owens, F. N., and R. Zinn. “ProteinMetabolism of Ruminant Animals.”In: D. C. Church (Ed.). The Rumi-nant Animal: Digestive Physiologyand Nutrition. pp. 227–249.Prentice-Hall, Englewood Cliffs, NJ.1988.

Pate, F. M., D. W. Sanson, and R. V.Machen. “Value of a MolassesMixture Containing Natural Proteinas a Supplement to Brood CowsOffered Low Quality Forages.” J.Anim. Sci. 68(1990):618–623.

Paterson, J. A., R. C. Cochran, and T.J. Klopfenstein. “Degradable andUndegradable Protein Responsesof Cattle Consuming Forage-BasedDiets.” In: M. B. Judkins and F. T.McCollum III (Eds.). Proc. 3rd

Grazing Livest. Nutr. Conf. Proc.West. Sec. Amer. Soc. Anim. Sci.47 (Suppl. 1, 1996.): 94–103.

Petersen, M. K., D. E. Hawkins, I.Tovar, and L. A. Appeddu. “Improv-ing Rebreeding with ProteinSupplements.” Western BeefProducer. 1st and 2nd Ed. February.1996.

Pitts, J. S., F. T. McCollum, and C. M.Britton. “Protein Supplementation ofSteers Grazing Tobosa Grass inSpring and Summer.” J. RangeManage. 45(1992):226–231.

Spitzer, J. C., D. G. Morrison, R. P.Wettemann, and L. C. Faulkner.“Reproductive Responses and CalfBirth and Weaning Weights asAffected by body Condition atParturition and Postpartum WeightGain in Primiparous Beef Cows.” J.Anim. Sci. 73(1995):1251–1257.

Sprinkle, J. E. “Matching ForageResources with Cow Herd Supple-mentation.” Univ. of ArizonaCooperative Extension PublicationNo. 195023. 8pp. 1996.



FROM:









INTRODUCTION

Breeding failure is the most importantadverse consequence to the cow herdduring drought. This is due to reducedforage quality and availability, resultingin nutritional stress. As forage qualitydecreases, lignin and other more slowlydigestible components of forageincrease. This lower quality forageremains longer in the rumen beforeexiting, reducing forage intake. Thus,the cow may be unable to eat enoughforage to maintain body weight(Figure 1).

During early to mid-lactation, a beefcow will consume from 2.5 to 3.0% ofher body weight in forage daily. Duringdrought, stocking rates may be adjustedto increase forage for each animal unit,but forage quality may drop therebypreventing adequate digestible nutrientintake. As forage digestibility drops,

passage rate of undigested dry matterdecreases and forage intake declines.In Montana, when forage digestibilitywas 61%, lactating cattle consumed 2.2to 2.8% of body weight in forage. Duringa drought year, forage digestibilitydropped to 43% and the same lactatingcattle consumed 1.2 to 1.3% of bodyweight in forage (Havstad andDoornbos, 1987). Forage intake at thislevel is inadequate to furnish thenecessary nutrients for milk productionand maintenance of cow body condition.To survive drought and maintainacceptable rebreeding percentages andeconomic viability, the cow herd shouldbe managed for acceptable bodycondition. Forage should also bemonitored for total production and

GENERAL RECOMMENDATIONS

1. Evaluate range to determine forage supply.

2. Analyze forage to determine nutrient deficiencies.

3. Start supplementation regime at least 60 days before calving to prevent accelerated weight lossfollowing calving.

4. If forage supply is adequate (less than 50% utilization of forage), supplement natural protein (22%crude protein or greater) to meet forage deficiencies (generally 1 to 2 lbs. of supplement per day fornonlactating cattle). Protein supplements can be given as infrequently as once a week.

5. If forage supply is limited, use a protein/energy or energy supplement. Energy supplements need tobe fed daily.

6. Use urea supplements with extreme caution.

7. Use water to help distribute livestock to underutilized areas of the grazing allotment.

8. Cull cows to match animal units to forage available. Cull in this order: open cows, old cows (9 yearsor older), 2-year-old producing cows, 3-year-old producing cows, replacement heifers.

9. Monitor use of toxic plants by cattle and move cattle if necessary to avoid over- consumption of toxicplants.

Figure 1. Forage Intake of a Lactating Range Cow

Forage Digestibility

1000 lb. cow milking 10 lbs./day


0

0.5

1

1.5

2

2.5

3

3.5

45 50 55 60 65

Amount Needed for Maintenance

Amount Can Eat

SUPPLEMENTATIONDURING DROUGHT

Jim Sprinkle1


14.92% by September following 2.32inches of moisture from July throughSeptember. At the lower elevation sitewith 50% of normal moisture, crudeprotein of the forage never got above4.4%. At the same low elevation sandyupland range site, even winterfat hadonly crude protein above 6% for onemonth (April 96; 7.23% crude protein).Conversely, the crude protein ofwinterfat at the site with 90% moisturenever fell below 6% and was above11% during April and May. Proteinrequired for a 1000 lb. nonlactating cowis around 1.6 lbs./ day or 7% crudeprotein in the diet. When the cow islactating, 2.0 lbs. or 9.6% dietary crudeprotein is required. Drought accentuatesthe need for protein supplementation.

Protein supplementation during droughtcan yield dividends. In a study at FortStanton, NM over several years ofdrought, weaning weights and conceptionrates for cattle of different ages werecompared (Table 1). The supplementedcows in this study were fed 1 lb. ofcottonseed meal per day from just priorto calving until grass was green. Theeffects of the drought were most severefor younger cows, but supplementationincreased weaning weights and con-ception rates in cows of all ages. Othercattle at risk during drought are heaviermilking cattle and larger framed cattle.It is well to remember that duringdrought we are not only supplementingto meet deficits in this year's forage, weare also supplementing next year’s calfcrop.

When forage contains less than 6%protein, protein supplementation can beeffective in enhancing forage intake(Caton et al., 1988). When additionalprotein is made available, this increasesthe number and activity of microorgan-isms in the rumen which are ultimatelyresponsible for fiber digestion. As themicrobial population of fiber digestingbacteria increases, passage rate offorage increases, ultimately allowing forgreater intake of low quality forage. Insome cases, greater digestibility of

quality to determine if the cow’s nutri-tional requirements are being met. Itmay be a cost effective practice toanalyze forage or fecal samples fortotal digestible nutrients (TDN) andcrude protein during dormancy ordrought and match supplementationstrategies to the nutritional deficits inthe forage. Your local CooperativeExtension office can provide addressesof laboratories which offer this service.

PROTEIN SUPPLEMENTATION

Figure 2 illustrates crude proteincontent of sand dropseed (sporoboluscryptandrus (Torr.) Gray; warm seasongrass) at two different range sites inArizona during the 1996 drought. Atone site, precipitation was 90% ofnormal and protein content increased to

Table 1. Production from Cows During Drought

Foster, 1996

No Supplement 1 lb./daycottonseed meal

Cow Age Weaning Conception Weaning Conception(Years) Weight Rate Weight Rate

(Lbs.) (%) (Lbs.) (%)

3 306 45 372 90

4 341 62 376 88

5 366 63 410 92

6 356 73 396 85

Arizona Strip Range Forage Quality Analysis Study (1996)

Crude Protein, %

Figure 2. Crude Protein in Arizona During Drought

Stocking Rate Sand dropseed (90% norm. precip.) Sand dropseed (50% norm. precip.)

Sandy Loam Upland (Calcareous. 4930') Sandy Upland (2150')


forage has also been observed. Figures3 and 4 illustrate how both forageintake and forage digestibility wereincreased by protein supplementationfor cattle eating poor quality (2% crudeprotein) prairie hay.

Steers fed the greatest amount of the33% protein supplement increasedforage intake 49% and had 39%greater digestibility of forage thancontrol steers. The amount of TDNrequired to maintain body weight fornonlactating cattle is around 52%, sosteers supplemented the highest levelof protein should not have experiencedweight loss (although these data werenot reported).

When a lower protein supplement(18%) was fed on an equal proteinbasis (1.7, 3.5, and 5.3 lbs. of supple-ment per day), forage intake was 1.34,1.48, and 1.33% of body weight foreach increasing supplementation level.Total ration digestibility was 41, 43, and50%, respectively. Cattle in this studyappeared to be limited in protein intakewith the low quality forage, and substi-tution of forage by supplement did notappear to occur with the higher proteinsupplement. In this same study, somesubstitution of forage by supplementresulted when alfalfa hay was fed at thesame rates as for the medium proteinsupplement. However, no substitutionoccurred when alfalfa pellets were fed,presumably because of a positive effecton rate of passage.

An advantage with protein supplemen-tation is that cattle can be supplementedas infrequently as once a week withoutdetrimental effect (Huston et al., 1997).This is not the case for energy supple-ments (e.g., corn, milo) which need tobe supplemented daily.

ENERGY SUPPLEMENTATION

It is generally acknowledged that forageintake and digestibility of the forage willdecrease with energy (grain) supple-mentation. However, sometimes the

Figure 3. Forage Intake on Dormant Tallgrass Prairie Hay1.9% Crude Protein; 38% TDN

Stafford et. al., March 1996 Journal of Animal Science

For

age

Inta

ke, %

of B

ody

Wei

ght

Lbs. of 33% Protein Supplement

Figure 4. Forage Digestibility on Dormant TallgrassPrairie Hay

1.9% Crude Protein; 38% TDN

Stafford et. al., March 1996 Journal of Animal Science


For

age

Dig

estib

ility

, TD

N%

value of the grain to the animal offersa greater advantage than the disad-vantage of lowering the forage value.Also, grain can be advantageous forstretching the forage supply. If foragequantity is insufficient, it is probablymore economical to supplement with acombination protein/energy ration (20to 25% protein; 40 to 50% grain) than ahigh protein ration. Cattle will beunable to capitalize on the benefitsof a high protein supplement whenthe forage supply is insufficient. As ageneral rule, if utilization of availableforage is less than 50%, use a highprotein ration, but if forage utilization is


equal to or greater than 50%, use aprotein/energy or energy supplement.

Figure 5 shows the energy content(TDN) of the same grass from the samesites as shown in Figure 2. The energyrequired for maintenance of lactatingcattle is supplied by forage at around56% TDN and for nonlactating around52% TDN. At no time during 1996 wasTDN above 49% for the low elevationrange site with 50% of normal precipita-tion. Assuming forage availability wasadequate, protein supplementation atthe low elevation range site couldpossibly have increased both foragedigestibility and intake to more optimallevels.

OTHER SUPPLEMENTS

In stressful situations in which cattle arelosing weight, some benefits have beendemonstrated by feeding supplementswith approximately 40 to 60% of theprotein being ruminally undegradable orbypass protein. Feedstuffs high inbypass protein include feather meal,blood meal, corn gluten meal, and fishmeal. Due to palatability problems,rendered animal products are usuallylimited to 25 to 30% of the total supple-ment and are combined with grainproducts to increase palatability.Petersen et al. (1996) reported thatweight loss has been reduced and

conception rates increased in severalexperiments by feeding bypass protein.However, they reported that bypassprotein supplementation only seems tobe effective when animals are losingweight. The additional cost per ton foradding bypass protein is around $50 to$80.

Another form of supplementation duringdrought to increase harvestable forageis the hauling of water to seldom usedareas of pastures. Granted, this is laborintensive and requires acreage which iseasily accessible. However, in largepastures with few water developments,this can help in grazing distribution. Inareas which are not excessivelyrugged, it is estimated that cattle willuse 80% of the allowed harvestableforage up to 1 mile from a watersource, but only 40% at 1.5 miles, and20% at 2 miles from the water source. Ifthere are areas in pastures exceeding 1mile from water, then in effect you havea “forage bank” which can be utilized.

In order to avoid harming the rangeresource for subsequent years, maxi-mum utilization of forage should notexceed 60% (Lacey, 1995). Exceptionsare crested wheatgrass (Lacey, 1995)and annuals. Annuals should be grazedearly and heavily during a drought yearwhile they are still green and havegreater nutritive values. Pasturesshould be rotated frequently andinclude longer rest periods due toreduced growth during drought. Insome instances, it may be advanta-geous to open up pastures into largerpastures to allow for more selectivity bycattle. This will also help prevent cattlefrom “bogging down” in earthen watertanks with dropping water levels.

UREA SUPPLEMENTS

When forage quality is low and the TDNor energy value of forage is low (lessthan 45%), it may be risky to feedprotein supplements with urea. How-ever, research in this area is ratherlimited (Dr. Bob Cochran, Kansas State

Figure 5. Energy Content in Arizona During Drought

Total Digestible Nutrients (TDN), %

Stocking Rate Sand dropseed (90% norm. precip.) Sand dropseed (50% norm. precip.)

Sandy Loam Upland (Calcareous. 4930') Sandy Upland (2150')

Arizona Strip Range Forage Quality Analysis Study (1996)


University, personal communication). Insome cases, urea toxicity may be morerelated to reduced forage availabilitythan to forage quality. A rule which iswidely quoted is that urea shouldconstitute no more than 1/3 of thecrude protein of a cow’s diet. If thisamount of urea in the diet is exceeded,there may be increased risk of ureatoxicity and death. Symptoms of ureatoxicity have been observed in cattleunaccustomed to urea in doses approxi-mating .4 lbs of urea (equivalent toapproximately 1.15 lbs. of crude proteinsupplied by urea) for a 1000 lb. cow(Radostits et al., 1994). If the proteinsupplement being fed contains 32%crude protein with 26.5% crude proteinbeing derived from urea, the cow eatingthis supplement may be at risk if sheconsumes 4.34 lbs. of the urea basedsupplement (4.34 lbs. supplement •.265 crude protein for urea = 1.15 lbs.equivalent protein from urea or .40 lbs.urea). The crude protein:urea ratio canbe determined by the feed tag, forageanalysis, estimated forage intake fromTable 2, disappearance of urea supple-ment, and the formula in the box right.

For example, forage analysis revealsthat the forage is estimated to contain5% crude protein and 45% TDN.Forage intake from Table 2 is estimatedto be 1.7% of body weight or 17 lbs. fora 1000 lb. cow. Crude protein intakefrom forage is 17 • .05 or .85 lbs. Thefeed tag on the supplement contains32% crude protein and 83% of this, or26.5% crude protein, is from urea. Thecattle are eating 4 lbs. of supplement aday, or .22 lbs. natural protein fromsupplement (4 • .055) and 1.06 lbs.protein from urea (4 • .265). The crudeprotein:urea ratio in this instance wouldbe greater than the desired 3:1 ratio.

(.85 + .22 + 1.06) = 2.00 1.06 1.00

If it is desired to continue feeding aurea based supplement in this case,then the amount of urea in the supple-ment needs to be reduced. If cattlewere fed a urea based supplement with

20% crude protein of which 70% of theration, or 14% crude protein, was fromurea, then cattle could probably con-sume 4 lbs. of this supplement. Ifforage quality drops to 4% crudeprotein and 40% TDN, then cattle canonly consume safely 2 lbs. of the 20%protein supplement.

The cutoff value for a urea basedsupplement with forage of 5% proteinand 45% TDN (15% increase in forageconsumption factored in for proteinsupplementation) is 2 lbs. of a 32%protein supplement with crude proteinfrom urea = 26.5% and 4.5 lbs. for a20% protein supplement with crudeprotein from urea = 14%.

One may be tempted to control theintake of liquid urea based supplements

(lbs. protein from forage + lbs. natural protein in supplement + lbs. protein from urea)

lbs. protein from urea

= 3.14

1.00

[(12 lbs. forage • .04) + (2 lbs. • .06 natural protein) + (2 lbs. • .14 urea)]

(2 lbs. • .14 urea)

1Research from various sources including Kronberg et al., 1986;Kragner et al., 1986; Havstad and Doornbos, 1987; Sprinkle, 1992.

Table 2. Forage Intake of Lactating Cattle at DifferentForage Digestibilities

Forage Amount Required to Eat Amount Can Eat at

Digestibility or to Meet Maintenance the Forage

TDN, % Requirements, % of Digestibility Listed,Body Weight % of Body Weight1

43 3.2 1.2 to 1.3

45 3.1 1.7 to 2.0

50 2.8 1.9 to 2.1

55 2.6 1.7 to 2.1

58 2.4 1.9 to 2.5

60 2.3 2.0 to 2.5

62 2.3 2.3 to 2.8

64 2.2 2.6 to 3.2

Greater than 64 2.6 to 3.2


by locking the wheels on the feeder.However, research suggests that after3 days of urea deletion from the diet,adaptation to urea based supplementsis lost (Davis and Roberts, 1959). It is amuch better practice to either eliminatecompletely the feeding of urea duringdrought or else significantly reduce theamount of urea in the supplement.

Signs of urea toxicity include rapid,labored breathing, muscle tremors,severe abdominal pain, frothing at themouth and nose, irritability to soundand movement to the point of beingaggressive, slight incoordinationfollowed by severe incoordination andthe inability to stand, weakness, bloat,and violent struggling and bellowing(Essig et. al, 1988; Radostits et al.,1994). Treatment, which is often toolate, is oral administration of 4 liters of a5% vinegar solution for a 1000 lb. cow(Davis and Roberts, 1959).

TOXIC PLANTS ANDADDITIONAL CAUTIONS

An additional caution for supplementa-tion during drought is to avoid feedingsupplements containing ionophores(trade names of Rumensin® orBovatec®). Doing so can increase theprobability of nitrate poisoning(Radostits et al., 1994). Nitrates canaccumulate in forage during drought,and especially in the “green-up” followingdrought. Plants which are particularlysusceptible to nitrate accumulationinclude kochia, lambsquarters, oat hay,Russian thistle (tumbleweed), sorghum,and filaree. Symptoms of nitratepoisoning are similar to other kinds ofpoisoning and include rapid pulse rate,labored breathing, and possibly muscletremors and convulsions. Symptomswhich are somewhat unique to nitratepoisoning include darkened mem-branes in the mouth, nose, and eyesand dark red to brown blood instead ofbright red blood (Essig et. al, 1988).Treatment is accomplished with intrave-nous injection of 100 ml of a 4%solution of methylene blue / 1000 lbs.

body weight (Essig et. al, 1988).According to Radostits et al. (1994),supplemental feeding of sodiumtungstate (wolfram) under veterinaryadvisement can reduce the effects ofnitrate poisoning in cattle grazingpastures with high levels of nitrate(greater than 1% nitrate nitrogen; Essiget al. 1988,).

During drought, one also needs to bealert to possibilities of toxic plantpoisoning. Oftentimes, the greenestplants may be toxic (e.g., bracken fern,whorled milkweed). Forage productionshould be monitored closely and cattleshould not be subjected to excessivestocking rates on the depressed foragebase. Be aware of poisonous plantswhich exist in your pastures andcarefully monitor the use of theseplants by livestock.

CONCLUSION

It is important to plan ahead whensupplementing cattle during drought.The most effective time to supplementcattle is before calving. It is almostimpossible to put weight back on a cowduring the first 45 to 60 days aftercalving. Nutrient requirements at thistime are about 50% greater than in thelast trimester of pregnancy. Producersshould analyze forage for deficits inprotein and TDN and supplementaccordingly to maintain cow weightbefore calving (Sprinkle, 1996). Repro-duction will drop sharply if cattle arethinner than a body condition score of 4at breeding.

It is acknowledged that drastic effectscan occur in a relatively short period oftime during drought. In some cases,cattle may be in adequate body condi-tion shortly before calving and loseweight rapidly as forage supplies andforage quality decline. Cattle shouldnot be allowed to get below a bodycondition score of 3 in order to avoidincreased susceptibility to diseases.Also, conception rates in cattle willpossibly drop to 40 to 50% at body


condition score 3 and to practically zeroat body condition score 2. If at allpossible, a cow should not beallowed to become protein deficientduring drought. For every 1 lb. ofprotein deficiency, the loss of 6.7 lbs. ofbody weight would be required tosupply this level of protein. Conversely,if the diet was deficient in energy(TDN), this would only require 1 lb. ofbody weight loss for each 1 lb. of TDN.If a cow was deficient in TDN by 1.5lbs. per day and initial body conditionscore was 4, the cow could lose 1.5 lbs.a day for 53 days and drop to a finalbody condition score of 3.

In the worse case scenario, some cattleshould be sold to stretch forage sup-plies while also feeding supplement toremaining cows to maintain desirablebody condition during breeding.Heavier milking and larger cattle wouldbe good candidates for culling, becausetheir maintenance requirements will bemuch larger. Since 2-year-old cows willrequire more supplementation and bemore difficult to rebreed, you may wantto consider selling these cows as well.Above all else, use pregnancy testingas a tool to reduce herd size andpreserve a reasonable calf crop thefollowing year. Income from sale ofcattle during drought may be eligible forincome deferment for 1 year if in anarea that has been declared a droughtdisaster area. If extreme destocking isexpected, early weaning of calvesshould be considered. Nonlactatingcattle will eat only 70% as much aslactating cattle, so this will spare theforage base somewhat during drought.

In conclusion, drought usually requiressome type of supplementation to avoidextreme weight loss in cattle. If cattleare allowed to become too thin, con-ception rates may decrease markedly.By obtaining forage or fecal samplesand analyzing for protein and TDN,supplements can be matched todrought conditions.

LITERATURE CITED

Caton, J.S., A.S. Freeman, and M.L.Galyean. 1988. "Influence of proteinsupplementation on forage intake,in situ forage disappearance,ruminal fermentation and digestapassage rates in steers grazingdormant blue grama rangeland."J. Anim. Sci. 66:2262-2271.

Davis, G.K., and H.F. Roberts. 1959.Univ. Florida Agr. Exp. Station Bull.611.

Essig, H.W., G.B. Huntington, R.J.Emerick, and J.R. Carlson. 1988."Nutritional problems related to thegastrointestinal tract." pp. 468-492.In: D.C. Church (Ed.) The Rumi-nant Animal: Digestive Physiologyand Nutrition. Prentice Hall,Englewood Cliffs, NJ.

Foster, L. 1996. "Cow herd nutritionduring a drought." Western BeefProducer. 2nd March.

Havstad, K.M., and D.E. Doornbos.1987. "Effect of biological type ongrazing behavior and energyintake." pp. 9-15. Proc. GrazingLivest. Nutr. Conf., July 23-24,1987, University of Wyoming,Laramie, WY.

Huston, J.E., H. Lippke, T.D.A. Forbes,J.W. Holloway, R.V. Machen, B.G.Warrington, K. Bales, S. Engdahl,C. Hensarling, P. Thompson, and D.Spiller. 1997. "Effects of frequencyof supplementation of adult cows inwestern Texas." Proc. West. Sec.Amer. Soc. Anim. Sci. 48:236-238.

Kronberg, S.L., K.M. Havstad, E.L.Ayers and D.E. Doornbos. 1986."Influence of breed on forage intakeof range beef cows." J. RangeManage. 39:421-423.


Lacey, J. 1995. "Tips for dealing withdrought in range." pp. CL1110.Cow-Calf Management Guide:Cattle Producer’s Library. Univer-sity of Idaho, Moscow, ID.

Petersen, M.K., D.E. Hawkins, I. Tovar,and L.A. Appeddu. 1996. "Improv-ing rebreeding with protein supple-ments." Western Beef Producer.1st and 2nd Ed. February.

Radostits, O.M., D.C. Blood, and C.C.Gay. 1994. Veterinary Medicine,8th Ed., Radostits, Blood, and Gay(Ed.). Bailliere Tindall, Philadelphia,PA.

Sprinkle, J.E., 1992. "Fecal output ofdifferent biological types of beefcattle on native range throughout aproduction year." M.S. Thesis.Montana State University,Bozeman.

Sprinkle, J.E. 1996. "Matching forageresources with cow herd supple-mentation." University of ArizonaCooperative Extension PublicationNo. 195023. 8 pp.

Stafford, S.D., R.C. Cochran, E.S.Vanzant, and J.O. Fritz. 1996."Evaluation of the potential ofsupplements to substitute for low-quality, Tallgrass-Prairie forage."J. Anim. Sci. 74:639-647.

Wagner, M.W., K.M. Havstad, D.E.Doornbos, and E.L. Ayers. 1986."Forage intake of rangeland beefcows with varying degrees ofcrossbred influence." J. Anim. Sci.63:1484-1490.



FROM:









MANAGING NUTRITIONALCHALLENGES TOREPRODUCTION

Jim Sprinkle1

INTRODUCTION

Nutritional challenges placed upon thelactating cow can be extreme in Arizona.Among these are the extra nutritionalrequirements caused by lactation.Figure 1 illustrates the weight losswhich usually occurs in a lactating cowduring the first 45 to 60 days of lacta-tion. At the period of time at which thecow has lost the most weight, produc-ers are trying to rebreed her in order tomaintain a yearly calving interval. It isusually not possible to entirely preventweight loss during early lactation withrange cattle. A better strategy is to planahead to allow for weight loss bybuilding or maintaining body fat storesbefore calving.

Another challenge with Arizonaranching operations is the reduction inforage quality with mature forage.Rainfall often occurs in a biannualpattern and forage quality before themonsoon rains and in late winter canbe low. As forage matures, protein,total digestible nutrients (TDN), andphosphorus often decline below levelsconsidered adequate. In addition,certain trace minerals may be deficientyear round. It is a good practice toanalyze dormant forage to determineprotein, TDN, and phosphorus content.You can then match cow supplementa-tion to the forage resource (SeeMatching Forage Resources with CowHerd Supplementation). It is also agood practice to analyze forage fortrace mineral status over two or threeyears to establish baseline data foryour ranch. Trace minerals in Arizonawhich may be of concern are selenium,copper, zinc, sulfur, and molybdenum.

There are several options one can taketo help meet the nutritional challengesplaced upon cows by lactation and theenvironment. Some of the most promi-nent are listed below and shall beexplained more fully:

1. Create a “fat storage cushion” forlactating cows by maintaining bodycondition score (1 to 9, 9 = fattest;Richards et al., 1986) at 5 or greaterbefore calving. As part of this strategy,utilize protein supplements for lowquality forage to increase forage intakeand digestibility.

2. If in spite of your best efforts, cattleare thin at breeding time, attempt to“flush” cattle with your best qualitypasture and/or by supplementation. Ifcombined with short-term calf removal,flushing will be more effective.

3. Match calving season to the foragecurve.

4. Genetically match the cow to theenvironment.

OPTION 1: MAINTAINING BODYCONDITION AT 5 BEFORE CALVING

As shown in Figure 1, it is an advan-tage to allow cattle to have fat reservesthey can mobilize during early lactation.Research has shown that reproductionwill suffer if cows are allowed to be-come too thin at calving, especially with

Figure 1. Milk Production, ForageIntake, and Body Weight Gain.

Milk Production

Weight Gain or Loss

Weaning

Forage Intake

After Coppock, 1985 (adjusted for beef animal)


ment should maintain body weight asthe energy requirement for nonlactatingcattle is around 52% TDN. Cattle fedless protein would probably loseweight; the greatest weight loss occur-ring with no protein supplement.Greater conception rates would beexpected for the cattle fed 2.7 lbs. ofprotein supplement. If management willallow it, it is cost effective to separatethin cows from fat cows before calvingand supplement protein to thin cowsaccording to forage deficits. Researchin West Texas (Huston et al., 1999) hasindicated that protein supplements canbe fed as infrequently as once a weekwithout detrimental effect. If energysupplements are fed (e.g., corn, milo),they need to be fed daily.

Conception rate will be improved bykeeping cattle in good body conditionprior to calving. Forage intake anddigestability can usually be improvedwith late season dormant foragethrough the use of protein supplements.Cost effective supplementation can beintegrated into prepartum nutritionalmanagement programs by analyzingforage for nutritional deficiencies andthen supplementing accordingly.

OPTION 2: FLUSHINGAFTER CALVING AND

SHORT TERM CALF REMOVAL

Table 2 shows the effect of flushing thincattle with a high energy ration aftercalving. Cattle in this study (Richards etal., 1986) were fed different levels ofenergy after calving. Two of the groupswere limit-fed a similar corn silage dietafter calving to lose 1.00 to 1.50 lbs. ofbody weight per day. Two weeks beforethe breeding season started, one ofthese two groups was then flushed with9 to 13 lbs. of corn and corn silage fedto appetite. The flushing ration wascontinued throughout the first 30 days ofthe breeding season. Both groups hadcalves removed from cow for 48 hourstwo days prior to the initiation of thebreeding season. Flushing and calfremoval had little effect upon cattle that

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gnideerBfo06yaDnosaeS nosaeS nosaeS nosaeS nosaeS

4 5±34 5±65

5 4±56 4±08

6 9±09 8±69

Table 1. Pregnancy % by Body Condition Score

Spitzer et al. May 1995. Journal of Animal Science

younger cows. Table 1 illustrates theeffects of different fat reserves withtwo-year-old cattle.

One problem faced in attempting tomaintain body condition at 5 beforecalving is that during the last trimesterof pregnancy forage quality can bequite low. As forage quality decreases,lignin and other more slowly digestiblecomponents of forage increase. Theresult of these changes in foragequality is that forage remains longer inthe rumen before exit, reducing forageintake. Thus, the cow may be unable toeat enough forage to maintain bodyweight (Figure 2).

When forage contains less than 6.25%protein, protein supplementation can beeffective. When additional protein ismade available in the rumen, thisincreases the synthesis of newmicroorganisms in the rumen whichare ultimately responsible for fiberdigestion. This is illustrated in Figures3 and 4 where forage intake andforage digestibility were increased byprotein supplementation for cattleeating poor quality (2% crude protein)prairie hay. For Arizona, data collectedby Cooperative Extension workers hasshown that the crude protein of bluegrama native range during the wintermonths of December to Februaryvaried between 1.58 and 7.55%.

In the above scenario, nonlactatingcattle fed 2.7 lbs. of protein supple-


were already in good condition atcalving but increased conceptionmarkedly for thin cattle. Although it maybe difficult to provide supplementation tocattle in extensive range operations, thisprinciple can be applied by usingexcellent quality pastures after calving.For instance, if filaree was in abundancein a particular pasture, it could be usedto help flush cattle before breeding.

Another tool that can be used incombination with flushng is short termcalf removal (Smith et al., 1979;Richards et al., 1986). If cattle arebeing worked for spring branding,calves could be separated from cowsfor 36 to 48 hours and not allowed tonurse. Research has shown this to beeffective in increasing estrus with thincows (body condition score 3 to 4; Nixet al., 1981). Researchers in Texashave shown that short term calf re-moval can be particularly effective withBrahman cross cattle which sometimeshave long periods of time before thefirst estrus postpartum (Nix et al.,1981). A note of caution: short term calfremoval with cows having a bodycondition score less than 4 may not beeffective in increasing conception rateunless cattle are provided with sometype of nutritional supplement as well(L. R. Sprott, Texas A & M University,personal communication). Additionalresearch in Australia has suggestedthat lactating Brahman and Brahmancross cattle will preferentially shuntnutrients from supplements into milk forthe calf (Hunter, 1991). Therefore, itmay be necessary to combine shortterm calf removal with flushing in orderto elicit a positive response for Brah-man crosses in any supplementationdone after calving. Researchers inTexas (Randel and Welker, 1980)compared Brahman x Hereford first-calfheifers fed at 125% of daily energyrequirements in a drylot and eitherexposed to normal calf suckling or once-daily suckling. At 90 days postcalving,100% of once-daily suckled heifers hadreturned to estrus compared to only35.3% of normal-suckled heifers.

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Table 2. Body Condition and Feeding Level(Pregnant 1 breeding)

1 The low energy diet consisted of a corn silage diet fed at approxi-mately 62% of daily requirements (if cattle weighed 1000 lbs. andwere milking 12 lbs. per day) from calving throughout the first 30days of breeding season. Cow that were flushed received the samediet until two weeks prior to the breeding season. At this time, cowsof the flushing diet received a diet that provided approximately 1.5times the daily energy requirement. The flushing diet was continuedthroughout the first 30 days of breeding. Both groups had calvesremoved from suckling for 48 hours at the initiation of breeding season.

OPTION 3: MATCH CALVINGSEASON TO FORAGE CURVE

From Figure 1, it would make senseboth physiologically and economicallyto match the calving season to times inwhich forage quality is at its peak. Infact, Deseret Ranches of Woodruff,Utah attributes moving calving forwardto match the forage curve as one of thekey ingredients in reducing cow costsand improving fertility (Simonds, 1991).

Figure 3 illustrates crude protein contentof forage produced and consumed by

Figure 2. Forage Intake of a Nonlactating Range Cow


Amount Needed for Maintenance

Amount Can Eat

Forage Digestibility1000 lb. cow


cattle on a Mohave County Ranch. Thedark line indicates the crude proteinrequirements at different times of theyear with estimated forage intakes atthese times. Composition of the dietwas determined on this chaparral-grassland ranch (4800 to 5500 ft.) bymicro histological analyses of fecalsamples. Crude protein of the dietchosen (light-colored line) was thendetermined by lab analyses of foragesamples. The diet chosen duringJanuary and February was 50 and 60%turbinella oak, respectively. In April, thediet consisted of 30% filaree and 30%ceanothus. Forage intake and fiber andprotein digestibility during January andFebruary would have been reduceddue to the negative effects of tanninspresent in turbinella oak. Crude proteincontent of filaree was very high in April(22.1%) and had a major effect oncrude protein of the diet consumed.Looking at Figure 5, it would appearthat the ideal time for calving would bein early March. This would allow fornutrition to be at its peak during the 60days preceding breeding. There arealso two times of the year in whichmanagement decisions would need tobe made. In January to February, itwould appear that protein supplementa-tion would be appropriate to preventaccelerated weight loss before calving.During June breeding season, supple-mentation decisions would be basedupon body condition. If cows hadgained sufficient weight during Marchand April, they would be able to coastthrough June without any supplementa-tion. However, if cows were slipping inbody condition in May or early June,supplementation would be advisable.Each ranch will be a little different in itsforage curve and it is a good idea toanalyze forage at different times of theyear to gain an understanding of theforage curve for that ranch. Matchingthe calving season to the forage curveshould improve cow nutrition andincrease the number and size of calvesweaned.

Figure 3. Mohave County Ranch

Protein in Forage vs Protein

January February March April June September OctoberCrude Protein Crude Protein in Diet

Chaparral to Grassland (4800 to 5500 ft.)

Cru

de P

rote

in

Figure 4. Forage Intake on Dormant TallgrassPrairie Hay

For

age

Inta

ke, %

of B

ody

Wei

ght

Lbs. of 33% Protein SupplementStafford et al., March 1996 Journal of Animal Science


For

age

Dig

estib

ility

TD

N %

Stafford et al., March 1996 Journal of Animal Science


Figure 5. Forage Digestibility on DormantTallgrass Prairie Hay



OPTION 4: MATCH THE COW TOTHE ENVIRONMENT

Cattle of intermediate size (1000 to1200 lbs.) and milk production (18 lbs.or less peak milk production per day)appear to work best in more aridenvironments. Low desert chapparalrangelands with limited herbaceousforage may require the use of smallframed cattle (850 to 900 lbs.) with lowmilk production (8 to 12 lbs. peak milkproduction). Modest increases in cowsize are accommodated more readilythan are increases in milk production.

If forage availability is not a problem,cattle with greater milk production canincrease forage intake to meetincreased energy demands due to milkproduction. In areas with greater rainfall(e.g., Midwest) this can be easilyaccomplished. In more arid areas of theWest, cattle with greater milk productionare often at a disadvantage. Eachadditional lb. of milk production (butter-fat content = 4.03%) would require anadditional .52 lbs. of forage intake ifforage TDN was equal to 56%. Byincreasing peak milk production by 2lbs. per day, calf weaning weights couldbe increased by 26 lbs. at 205 dayswhile also increasing forage demand ofthe cow by 1.04 lbs. per day. If the cowwas unable to satisfy this demand dueto constraints placed upon her bylesser forage quality and quantity,weight loss would occur.

Table 3 compares a hypothetical cowwith peak milk production of 19 lbs. toone with peak milk production of 21 lbs.Forage TDN ranged from 50 to 62% inthis example and forage intake wasadjusted downward in December,January, and February. In this fictitiousexample, cattle were supplementedwith adequate protein in January andFebruary to maintain weight as shownin the last column. Cattle in thisexample had a frame score of 4 with aweight of 1103 lbs. at a body conditionscore of 5 (Fox et al., 1988). Theaverage weight difference between

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.ceD 25 9.91 0 629 2401

Table 3. Comparison of Increasing Milk Production


body condition scores (1 to 9) was 86lbs. The cow with the lower milkproduction achieved a body conditionscore of 5 at the end of the year withsupplementation in January andFebruary. The cow with increased milkproduction had less body condition atthe end of the year, being approxi-mately 4.25 at 1042 lbs. At breedingtime in June, the cow with greater milkproduction would have a body conditionscore of 3.7 as compared to 4.4 for theother cow. If we assume a modestdecrease in conception from 85 to 77%for greater milk production, there wouldbe a net loss of $1269.80 for 100 cowswith the following parameters: 477 lb.weaning weight for lesser milk produc-tion, 503 lb. weaning weight for greatermilk production, 70¢ per lb. calves.

(477 lbs. • .85 • .70 • 100) - (503 lbs. •.77 • .70 • 100) = $ 1269.80

In Table 3, cattle with greater milkproduction were not adjusted upwardsfor greater forage intake to show theeffects of greater milk production in amore limiting environment. In periods oftime with better forage quality andadequate forage availability, cattle withgreater milk production can havegreater forage intake. Therefore, weightloss could be somewhat less than thatprojected in Table 3. However, theextra milk production would result ingreater weight loss for these cattle andmost likely would result in lower bodycondition at the end of the year. Ulti-mately, it is expected that the greatermilk production cattle would weanfewer lbs. of calf per cow exposed.

Cattle can be selected to matchArizona’s environment. Data is availablefrom the Meat Animal Research Centerof Clay Center, Nebraska to comparebreeds for different traits (http://www.ansi.okstate.edu/breeds/research/marccomp.htm). Selection withinbreeds can also be practiced by usingEPDs (Expected Progeny Differences)as a selection criteria (Sprinkle, 1996b)for targeting production goals. Important

traits to set selection criteria for toachieve optimum reproduction inArizona could include fleshing ability,mature size, milk production, andlongevity. If cattle are not properlymatched to our Arizona environment,an additional handicap is placed on thecowherd during years with unfavorableprecipitation. On average, this occurs inArizona four years out of ten (Holocheket al., 1998).

CONCLUSION

Maintaining body condition at a score of5 at calving should help enhanceconception rates for Arizona rangecattle. A key component of manage-ment is to have a knowledge of foragequality at different times of the year.Supplementation and calving seasoncan then be matched to the forageresource. Finally, matching the cow tothe environment can help overcomenutritional challenges to reproduction.

LITERATURE CITED

Coppock, C. E. 1985. "Energy nutritionand metabolism of the lactatingdairy cow." J. Dairy Sci. 68:3403-3410.

Fox, D. G., C. J. Sniffen, and J. D.O’Conner. 1988. "Adjustingnutrient requirements of beefcattle for animal andenviromnental variations." J.Anim. Sci. 66:1475-1495.

Hunter, R. A. 1991. "Strategic supple-mentation for survival, reproduc-tion and growth of cattle." pp.32-47. Proc. Grazing Livest.Nutr. Conf., August 2-3, 1991,Oklahoma State University,Stillwater.

Huston, J. E., H. Lippke, T. D. A.Forbes, J. W. Holloway, and R.V. Machen. 1999. "Effects ofsupplemental feeding interval onadult cows in western Texas." J.Anim. Sci. 77:3057-3067.



Holechek, J. L., R. D. Pieper, and C. H.Herbel. 1998. Range Manage-ment Principles and Practices.3rd Ed. Prentice Hall,Englewood Cliffs, NJ. 542 pp.

Nix, K. J., S. Roberts, and J. N.Wiltbank. 1981. "Using short-term calf removal and flushing toimprove pregnancy rate." BeefCattle Research in Texas, TexasAgricultural Experiment Station,College Station.

Handel, R. D., and G. A. Welker. 1980."Effect of once-daily suckling onpostpartum interval and cow-calfperformance." Beef CattleResearch in Texas, TexasAgricultural Experiment Station,College Station.

Richards, M. W., J. C. Spitzer, and M.B. Warner. 1986. "Effect ofvarying levels of postpartumnutrition and body condition atcalving on subsequent reproduc-tive performance in beef cattle."J. Anim. Sci. 62:300-306.

Simonds, Gregg. 1991. "Matchingcattle nutrient requirements to aranch’s forage resource, or 'Whywe calve late.'" Proc. RangeBeef Cow Symposium XII. pp209-216. Colorado Sate Univ.,Fort Collins.

Smith, M. F., W. C. Burrell, L. D. Shipp,L. R Sprott, W. N. Songster, andJ. N. Wiltbank. 1979. "Hormonetreatments and use of calfremoval in postpartum beefcows." J. Anim. Sci. 48:1285-1294.

Spitzer, J. C., D. G. Morrison, R P.Wettemann, and L. C. Faulkner.1995. "Reproductive responsesand calf birth and weaningweights as affected by bodycondition at parturition andpostpartum weight gain inprinuparous beef cows." J.Anim. Sci. 73:1251-1257.

Sprinkle, J. E. 1996a. "Matching forageresources with cow herd supple-mentation." Univ. of ArizonaCooperative Extension Publica-tion No. 195023. 8pp.

Sprinkle, J. E. 1996b. "UnderstandingEPDs." Univ. of Arizona Coop-erative Extension PublicationNo. 196011. l3pp.

Stafford, S. D., R. C. Cochran, E. S.Vanzant, and J. 0. Fritz. 1996."Evaluation of the potential ofsupplements to substitute forlow-quality, tallgrass-prairieforage." J. Anim. Sci. 74:639-647.


FROM:








INTRODUCTION

Heifer development is one of the threelargest expenses for beef cattle opera-tions when the opportunity cost forretaining heifers is factored in. You canpurchase replacement heifers ofbreeding size or develop your ownheifers in the feedlot, farm dry lot,irrigated pasture, or on range. In someareas of the country, companies whichdevelop ranchers’ heifers for a fee areavailable as well. The option youchoose depends upon the timetabledesired for heifer replacements and theeconomics of each option for a particu-lar operation. Unless hampered by alack of good quality, inexpensive feed,there is usually a cost advantage indeveloping heifers from the herdinstead of purchasing them. An addi-tional advantage is that you haveknowledge of the performance ofselected females’ dams and the abilityto more closely match replacementfemales to the particular environment.Inexpensive computer programs orworksheets are available ($1 forpublication, $20 for computer program,Willett and Nelson, 1992) which allowyou to calculate the costs of buying vs.retaining replacement heifers.

It has been well documented that inorder to achieve puberty, heifers needto weigh around 60 to 65% of matureweight at breeding time. For Britishbreeds this is around 650 to 700 lbs. ataround 14 to 15 months, and forContinental breeds, 750 to 800 lbs. atthe same age. (There are exceptions tothis rule; a small percentage of heiferswill be pubertal while still nursing).Achieving this level of weight gainfollowing weaning is rather easy in the

feedlot, dry lot, and possibly irrigatedpasture, but can be rather difficult onrangelands with poor quality winterforage. The disadvantage with feedlotdevelopment is cost. One Arizonabreeder calculated that when he utilizedfeedlot development of replacementheifers, the cost per pregnancy (90%conception rate) was over $160 com-pared to a little over $60 per pregnancyfor heifer development on pasture withsupplement (85% conception rate).

RANGE LIMITATIONS

The difficulty in developing replacementheifers on low quality feed is illustratedby Figure 1. The lower portion of eachbar represents the amount of forage a500 lb. heifer would have to eat of agiven forage quality in order to maintainbody weight. The shaded portion ofeach bar represents the amount ofadditional forage the heifer would haveto eat in order to gain .5 lbs./day, areasonable expectation for weight gainon winter range. The solid line repre-sents the amount of forage a heifer canactually eat for that particular foragequality. With lower quality forages,forage intake could possibly be in-creased 10 to 15% by protein supple-mentation. However, from this diagram itcan be seen that the heifer may not beable to gain any weight until foragequality approaches 56% digestibility.What often happens with heifers

Figure 1. Heifer Development on Rangeland

500 lb. Heifer to Gain .5 lbs/day

Dry Matter Forage Intake Required, lbs.

Gain

Maintenance

DM Intake Possible

Forage TDN %

HEIFER DEVELOPMENTON RANGELAND

Jim Sprinkle1


developed on native range is thatreplacement heifers will often coastthrough the winter with no weight gainor a slight weight loss and then startgaining weight following “green up.”This makes it difficult to achieve weightgains needed to get heifers cycling forearly breeding. Table 1 presents somerough projections of anticipated weightgains with different forage qualities.From this, it should be quite clear thatheifer development on rangeland usuallyrequires some type of supplementationin addition to forage consumption.

Tables 2 and 3 contain data for twodifferent studies relating to heiferdevelopment. Table 2 comparesheifers at San Carlos (Ray et al., 1993)fed either 0, 4.2, or 5.6 lbs./day of aprotein-energy supplement with 65%milo and 25% cottonseed meal (24%total crude protein). Heifers weighedaround 400 lbs. at weaning and heifersgained -.21, .43, and .66 lbs./day for 0,4.2, and 5.6 lbs. of supplement.Beginning in May, heifers were ex-posed to bulls for 60 days. Althoughthe authors did not report weights atbreeding, it is assumed that the weightswere less than ideal target weights.None of the control heifers conceived,compared to 31% and 54% for the lowand high feeding levels. However, dueto small size of heifers at calving,approximately one-third of the heiferslost calves at or shortly after calving.

Table 3 reports the findings ofLemenager et al. (1980). Cattle in thisstudy were fed poor quality fescue hay(9%, 8.5%, and 8.8% crude protein fortrials 1, 2, and 3, respectively; TDN notdetermined). Heifers in this studyappeared to be deficient in both proteinand energy. When the control heifershad 1.8 lbs. of protein supplementadded to their diet, they went from asmall weight loss to an average dailygain of around .5 lbs. Addition ofprotein also nearly doubled weightgains for animals fed corn. If controlheifers in this study had been able toeat 2% of their body weight daily, they

Table 1. Forage Quality and Heifer Weight Gainsa

a 500 lb. medium frame heifer with no supplementation, approximate McalME required for maintenance=10.64/day.

b TDN=total digestible nutrients, ME=metabolizable energy,Mcal=megacalories (1,000,000 calories), Ne

g=net energy for gain. Each 1

lb. of gain requires 2.1 Mcal of Neg. Ne

g is energy available for gain after

satisfying maintenance demands.c Estimates of forage intake at different forage digestibilities are best guesses

based upon the following research: Kronberg et al., 1986; Wagner et al.,1986; Havstad and Doornbos, 1987; and Sprinkle, 1992.

d Gain will probably be greater due to greater forage intake at this foragequality. If a heifer eats 13 lbs. of forage/day, average daily gain will beapproximately .4 lbs./day. High growth potential cattle may exceed this gainprojection.

Study by University of Arizona, Ray et al.,1993, AZ Ranchers’ Management Guide

Table 2. Heifer Development on the R100

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would have had nearly adequate crudeprotein intake during trial 1, (althoughnot all the protein may have beenavailable) and would have been slightlydeficient in crude protein in the othertrials if no additional protein weresupplied. In reality, forage intake duringtrials 1 and 2 may have been less than2% of body weight. The addition ofsupplemental protein during trial 3could possibly have increased bothdigestibility and forage intake. Heifersin this study were placed on goodquality pasture following the study andpasture bred for 60 days. The heifersreceiving lesser amounts of supplementduring the winter exhibited compensa-tory gain while on pasture. Weightgains on pasture averaged over allyears were 1.7, 1.5, and 1.3 lbs. forheifers fed 0, 2.7, and 5.4 lbs. of cornduring the winter, respectively. Pooleddata over all three years had 69%, 74%,and 84% conception for the heifers fed0, 2.7, and 5.4 lbs. of corn per day.

UNIVERSITY OF NEVADA STRATEGY

Heifers in the Lemenager et al. (1980)study performed better than the SanCarlos study (Ray et al., 1993) due tobeing larger at the beginning of thefeeding period. Heifers need to reachan age and weight threshold to initiate

Table 3. Heifer Development with Different Levels of Corn

Lemenager et al., 1980. Journal of Animal Science

puberty (Table 4). Chronic feed restric-tion will prevent or delay puberty inheifers. The University of Nevada,Reno (Torell et al., 1993) has devel-oped a 4 point plan for heifer develop-ment with smaller framed range cattle.

1) Meet target weight of 600 lbs. atbreeding time.

2) Have heifers at a body conditionscore of 5 or greater at breeding.

3) Have heifers at a reproductive tractscore (LeFever and Odde, 1986) of3 or greater at breeding. (Noimmature uterine tracts with lessthan 3/4" diameter uterine hornsand no tone).

4) To ensure less calving difficulty,make sure pelvic areas exceed150 sq. cm at 12 months of age.

Following these guidelines will improvereproductive success with replacementheifers. It is also important to avoidnutritionally stressing replacementheifers after breeding and prior tocalving. This will reduce growth in thepelvic opening and nullify attempts tomanage for less calving difficulty.

FEEDING STRATEGY

Achieving acceptable weight gains onwinter range in order to reach target


weights for puberty can be a challenge.If weaned heifers weigh from 450 to500 lbs. in late October and the targetweight for breeding in June is 650 lbs.,then heifers need to gain from .7 to 1.0lbs. per day. Achieving this level of gainwill enhance fertility by allowing heifersto have at least one heat cycle beforethe breeding season starts.

Based upon computer modeling andlimited research data available forArizona rangelands, weight gains thatcan be expected on moderate qualitywinter range (50% TDN, 5% crudeprotein) in conjunction with 4.5 to 5.0lbs. of supplement (protein or protein/energy) per day would be around .5 lbs.of weight gain per day. If the supple-ment costs $180 per ton, daily cost ofthe supplement alone would be from$0.41 to $0.45 per head per day.

Replacement heifers can be placed in adry lot during the time period whenwinter forage quality is poor andachieve weight gains of 1 lb. per day ona high roughage diet (less than 20%

grain) at a cost of $0.72 to $0.82 perhead per day (based upon feed costs of$100 per ton or good quality alfalfa hayand $10 per cwt. for grain). Dependingupon the genetics of your herd and thequality of your hay, you may be able toachieve this rate of gain with little or nograin. If you desire to increase averagedaily gain to 1.5 lbs. per day, this wouldrequire an additional 1.7 lbs. of corn,2.3 lbs. of cottonseed meal, or 5.3 lbs.of good quality alfalfa hay. This is inaddition to the 14.4 lbs. of feed previ-ously allocated for a 600 lb. heifer fedin the dry lot.

An ideal strategy for meeting targetbreeding weights when developingheifers on rangeland could be asfollows. After calves have the “bawl”out, turn them into excellent qualityriparian pastures (rested all year forwinter grazing) or on hay stubble forabout a month (November) or untilforage utilization goals are reached.When forage quality declines signifi-cantly on rangeland (approximatelyNovember 1 to February 15 for lowelevation or November 1 to March 15for high elevation range sites), feedheifers in a dry lot with excellent qualityhay. If winter precipitation is favorableand annual grasses are growing well,turn the heifers out after the dry lotfeeding period to utilize the cheaprange forage. Heifers will exhibitcompensatory gain when placed onexcellent quality forage. If average dailygain on spring pasture is 1.2 lbs. perday for 75 days, then weight gains inearly winter for 450 to 500 lb. Britishcross replacements will only need to befrom .5 to .9 lbs. per day. By monitoringweight gains regularly and by looking atforage quality and quantity closely, youwill be able to decide when grazingwinter range is appropriate and whenadditional feed is required.

Since you will probably have to supple-ment your replacement heifers toachieve desired weight gains beforebreeding, you may want to consideradding an ionophore (Rumensin® or

deerB,.soM5.31latrebup% latrebup% latrebup% latrebup% latrebup%

detsujdA,ega ,ega ,ega ,ega ,ega a syad

detsujdA,.tW ,.tW ,.tW ,.tW ,.tW a .sbl

lloPdeR 6.88 953 056

drofereH 9.93 114 596

sugnA 4.75 393 796

nisuomiL 0.44 804 347

heivnuarB 2.49 053 237

reuagzniP 1.29 063 937

heivbleG 9.29 353 547

latnemmiS 8.68 363 857

sialorahC 6.06 193 418

latnenitnoC%57,etisopmoC 8.58 663 567

latnenitnoC%05,etisopmoC 3.98 163 837

hsitirB%57,etisopmoC 0.48 863 327

Table 4. Puberty Traits

aAdjusted to 100% puberty basis.Gregory et al., 1995. USDA-MARC, Clay Center, Nebraska


Bovatec®) to the grain, protein, or liquidmolasses supplement. In a recentreview in the Oct. 21, 1996 issue ofFeedstuffs, Huntington reported thatgrazing ruminant animals supple-mented with ionophores had increasednitrogen digestibility and 6% greaterweight gains than controls. Thesefindings were determined on more than2,000 cattle in over 30 studies.

An additional advantage which hasbeen observed by feeding Rumensin®to replacement heifers may be induce-ment of puberty at an earlier age(Lalman, et al., 1993).

CONCLUSION

When considering a breeding program,you may wish to use breed combina-tions to improve puberty traits. Table 4shows that there is a great deal ofvariation in puberty traits for the percent-age of females showing estrus at 13.5months. Dual purpose breeds of cattlegenerally express puberty earlier thanmost other breeds except Red Poll. Youmay desire to include a percentage ofone of the earlier puberty breeds in yourbreeding herd if you need to improveconception for yearling heifers.

When replacement heifers are selectedat weaning, weigh the heifers and thendetermine how much weight heifers willneed to gain by breeding time (seeTable 4). Next, count the number ofdays until the start of breeding time andcalculate average daily gain needed.Target weights for heifers should beachieved at least one heat cycle (21days) prior to the start of breedingseason. It is to your advantage to selectheavier heifers (at least 450 to 500 lbs.)so that the desired weight gain can beachieved without excessive cost. Tailorthe heifer development program so thatthe feeding program will accommodatethe desired weight gains withoutallowing heifers to get too fat. If heifersgain weight too rapidly, it will increasefeed costs and decrease lifetimeproductivity due to excessive fat

deposition in the udder. Feeding tablesare available from the National Re-search Council or your local Coopera-tive Extension office which will predictthe nutrient requirements needed foryour heifer development feedingprogram.

I would recommend that if you developbreeding heifers on rangeland that youanalyze forage for protein and TDN andsupplement accordingly. Supplement toachieve desired weight gain accordingto “Matching Forage Resources withCow Herd Supplementation,” in thisGuide. Do not let heifers becomedeficient in protein, or weight loss willaccelerate. Keep mineral supplementsout to heifers according to mineraldeficiencies in your area by season ofthe year. Certain areas of Arizona aredeficient in selenium, copper, or zinc,and most areas will be deficient inphosphorus when forage is dormant. Ifyou need help in balancing rations foryour forage base, contact your localextension office.

Though the Nevada system of heiferdevelopment works for the most part,scoring reproductive tracts has limitedvalue for Arizona. However, havingheifers in good body condition andselecting for adequate pelvic area aregood management practices to follow.The bottom line is to achieve targetbreeding weights and ages in replace-ment heifers at breeding time (Table 4).Combined with genetic selection forpuberty and matching forage deficits tonutritional supplements, heifer develop-ment on rangelands can be made morecost effective.

LITERATURE CITED

Gregory, K. E., L. V. Cundiff and R. M.Koch. “Composite Breeds to UseHeterosis and Breed Differences toImprove Efficiency of Beef Produc-tion.” Roman L. Hruska U. S. MeatAnimal Research Center, Agricul-tural Research Service, USDA,Clay Center, NB. 1995.


Havstad, K. M., and D. E. Doornbos.“Effect of Biological Type onGrazing Behavior and EnergyIntake.” In: M. K. Judkins, D. C.Clanton, M. K. Petersen, and J. D.Wallace (Ed.) Proc. Grazing Livest.Nutr. Conf. pp. 9-15. Univ. ofWyoming, Laramie, WY. 1987.

Huntington, G. B. 1996. “GrazingRuminant Response to IonophoresAffected by Management, Environ-ment.” Feedstuffs. October 21,1996.

Lalman, D. L., M. K. Petersen, R. P.Ansotegui, M. W. Tess, C. K. Clark,and J. S. Wiley. “The Effects ofRuminally Undegradeable Protein,Propionic Acid, and Monensin onPuberty and Pregnancy in BeefHeifers.” J. Anim. Sci.71(1993):2843-2852.

LeFever, D. G. and K. G. Odde.“Predicting Rreproductive Perfor-mance in Beef Heifers by Repro-ductive Tract Evaluation BeforeBreeding.” pp. 13-15. CSU BeefProgram Report, Colorado StateUniversity, Fort Collins. 1986.

Lemenager, R. P., W. H. Smith, T. G.Martin, W. L. Singleton, and J. R.Hodges. “Effects of Winter andSummer Energy Levels on HeiferGrowth and Reproductive Perfor-mance.” J. Anim. Sci.51(1980):837-842.

Kronberg, S. L., K. M. Havstad, E. L.Ayers, and D. E. Doornbos. “Influ-ence of Breed on Forage Intake ofRange Beef Cows.” J. RangeManage. 39(1986):421-423.

Ray, D. E., A. M. Lane, C. B. Roubicek,and R W. Rice. “Breeding YearlingHeifers.” Arizona Ranchers’ Man-agement Guide, University ofArizona, Tucson. 1993.

Sprinkle, J. E. “Fecal Output of DifferentBiological Types of Beef Cattle onNative Range Throughout aProduction Year.” M. S. Thesis.Montana State University,Bozeman. 1992.

Sprinkle, J. E. “Matching ForageResources with Cow Herd Supple-mentation.” University of ArizonaCooperative Extension PublicationNo. 195023. 8 pp. 1996.

Torell, R. C., L. J. Krysl, K. E. Conley,G. M. Veserat, J. W. Burkhardt, W.G. Kvasnicka, and J. Wilker. “HeiferDevelopment under a WesternRange Environment 1. Growth andEstrus Synchronization.” Proc.West. Sec. Amer. Soc. Anim. Sci.44(1993):356-359.

Wagner, M. W., K. M. Havstad, D. E.Doornbos, and E. L. Ayers. “ForageIntake of Rangeland Beef Cowswith Varying Degrees of CrossbredInfluence.” J. Anim. Sci.63(1986):1484-1490.

Willett, G. S., and D. D. Nelson. “Raiseor Buy Replacements?” WashingtonState Cooperative ExtensionBulletin No. 1710, Department ofAgricultural Economics, HulbertHall, Washington State University,Pullman, WA 99164-6210. 1992.



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