Strategies for Successful Development of Beef Heifers 1

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1 SS-ANS-15 Strtegies for Successful Development of Beef Heifers 1 W.E. Kunkle, R.S. Snd nd P. Grces-Yepez 2 Introduction The best ge to breed heifers for their first clf depends on the prticulr sitution on ech frm. Most beef producers cross the U.S. breed yerling heifers to clve t two yers of ge. In Florid nd cross the southern gulf cost region, cttle production systems hve t lest two mjor differences from those in temperte res of the United Sttes. First, forge nutrition levels of the tropicl wrm seson forges re lower thn those of forges grown in the cooler nd/or lower rinfll res of the U.S.; therefore, more supplement is required to dequtely grow heifers. Second, the use of some level of Brhmn breeding in most of the cttle reduces the proportion tht rech puberty by 14 to 15 months. This increses the costs nd reduces the success, therefore clving t 2 yers of ge is unprofitble in some situtions. The extr costs involve dditionl plnting of nnul forges, supplementl feeds, lbor, fcilities nd supplies. The extr income when considering clving t 2 yers of ge depends on the percent of heifers reching puberty nd becoming pregnnt, number of live clves born nd rised to wening, wening weight, clf price, percent of first clf heifers rebreeding nd the weight of cows when culled. If heifers re intended to be bred t 26 to 28 months of ge to clve t 3 yers of ge, the growth rte the first winter fter wening cn be s low s.25 to.50 lb/dy. When dequte quntities of moderte qulity forge re vilble, these gins cn be chieved by feeding.3 to.4 lb/dy of nturl protein nd complete minerl supplement offered free choice. Clving t 2 yers of ge requires high level of mngement to be successful nd profitble. Severl Florid producers re successfully nd profitbly clving heifers t two yers of ge, but this is chllenge for the best mngers. This pper will focus on nutrition nd mngement progrms tht should contribute to successfully nd profitbly breeding heifers s yerlings to clve t two yers of ge. The mngement prctices discussed hve reserch showing their benefit in improving productivity or reducing costs, but not ll prctices will be pplicble to ll situtions. 1. This document is SS-ANS-15, one of series of the Deprtment of Animl Sciences, Florid Coopertive Extension Service, Institute of Food nd Agriculturl Sciences, University of Florid, Published My Updted April Plese visit the EDIS Website t 2. W.E. Kunkle, Professor nd Extension Beef Specilist, R.S. Snd, Associte Professor nd Livestock Specilist nd P. Grces-Yepez, former Grdute Student in the Deprtment of Animl Sciences, Florid Coopertive Extension Service, Institute of Food nd Agriculturl Sciences, University of Florid, Ginesville, The use of trde nmes in this publiction is solely for the purpose of providing specific informtion. UF/IFAS does not gurntee or wrrnty the products nmed, nd references to them in this publiction does not signify our pprovl to the exclusion of other products of suitble composition. The Institute of Food nd Agriculturl Sciences (IFAS) is n Equl Employment Opportunity - Affirmtive Action Employer uthorized to provide reserch, eductionl informtion nd other services only to individuls nd institutions tht function without regrd to rce, creed, color, religion, ge, disbility, sex, sexul orienttion, mritl sttus, ntionl origin, politicl opinions or ffilitions. For informtion on obtining other extension publictions, contct your county Coopertive Extension Service office. Florid Coopertive Extension Service / Institute of Food nd Agriculturl Sciences / University of Florid / Lrry R. Arrington, Interim Den

2 Strtegies for Successful Development of Beef Heifers 2 Breed Type nd Trget Weights Breed type influences the ge nd weight when heifers will breed. It is recommended tht heifers contin 50% or less Brhmn or other lter mturing breeds to ensure tht high proportion will rech puberty by 14 months. If less thn 75% of the heifers will rech puberty t the beginning of breeding seson even when developed to the trget weights, then the dded costs often will be more thn dded income from the clves. This sitution often occurs when heifers re over 50% Brhmn breeding (Rndel, 1994; Short et l., 1994) or other lter mturing breeds, especilly when they hve not been selected for erly puberty. An indictor of erly mturity is the scrotl circumference of the herd sire (Brinks, 1994). Sires with lrge yerling scrotl circumference produce heifers tht rech puberty t n erlier ge. A yerling (12-month) scrotl circumference of 34 centimeters or lrger is recommended for sires intended to produce heifers to clve t 2 yers of ge. Trget weights for successful development of heifers should be bsed on the immture weights with minimum trgets of 45% t wening, 65% t beginning of breeding seson nd 85% t clving. An exmple progrm using this pproch is shown in Tble 1. It is suggested tht heifers be selected tht re 45% or more of their mture weight t wening, or over 450 lb for typicl crossbred cttle in Florid. Heifers meeting these criteri should be grown to 65% or more of their mture weight by 14 months of ge (650 lb for typicl crossbred cttle). As n exmple, if heifers were wened in mid-september (450 lb) nd the breeding seson strted in mid-mrch (6 months fter wening), the heifers would need to gin 1.1 lb/dy to verge 650 lb t the beginning of breeding seson (Tble 1). Nutrition - A Key to Success The TDN requirements for heifers increse with higher weights nd higher gins (Tble 2). Mny residul pstures nd hys vilble during the fll nd winter hve TDN concentrtion of 50% or lower. Forges with lower TDN concentrtions lso hve lower levels of intke. The Florid Forge Testing Progrm nlyzes forges nd estimtes TDN concentrtion, intke of forge nd Qulity Index. Qulity Index is the TDN intke of forge offered free choice s rtio of the mintennce requirement of the heifer. A Qulity Index of 1.0 would be expected to meet the mintennce requirements of the heifer but llow no weight gin. Forge TDN concentrtions re estimted from invitro orgnic mtter digestibility nd the Qulity Index is estimted from both the neutrl detergent fiber (NDF) nd invitro orgnic mtter digestibility of the forge. The mount of supplement needed to grow heifers t 1.0 or 1.5 lb/dy for 3 different forge qulities is shown in Tble 3. A forge such s residul bhigrss psture in the fll or mture hys often hs qulity index ner 1.0 nd would require 6 lb/dy of 75% TDN supplement contining 15% crude protein for heifers to gin 1.0 lb/dy. An estimted 10 lb/dy of 75% TDN supplement contining 13% crude protein would be needed for the heifers to gin 1.5 lb/dy. A supplement contining corn, soyben mel nd minerls would contin pproximtely 75% TDN. It would require proportionlly more supplement for those contining TDN concentrtions under 75%. The levels of supplement nd protein concentrtion in the supplement re lower for higher qulity forges, which provides n economic incentive to mnge psture nd hy for high qulity. Supplements with high grin content hve high TDN levels nd high levels of strch. High levels of strch nd sugr ferment rpidly, resulting in lower rumen ph. This results in lower intke nd lower digestibility of forge when strch intke reches criticl level. Reserch using byproduct feeds tht hve low levels of strch but reltively high TDN hs shown tht these feeds hve less negtive effect on forge intke nd digestibility, resulting in better response thn expected from the level of TDN in these feeds. Recently comprison ws conducted in which corn, whet middlings nd soyben hulls were fed t pproximtely.5% or 1% of body weight to growing steers offered good qulity bermudgrss hy free-choice. The comprison showed tht gins, forge intke nd NDF digestibility were similr for ll three concentrtes fed t pproximtely.5% body weight (Tble 4). However, cttle fed corn t.94% of body weight hd lower gins, reduced forge intke

3 Strtegies for Successful Development of Beef Heifers 3 nd lower NDF digestibility thn cttle fed soyben hulls t 1.16% body weight (supplementl TDN from soyben hulls nd corn were similr). Cttle fed whet middlings hd responses intermedite to corn nd soyben hulls. Feeds such s soyben hulls, citrus pulp nd whet middlings re highly digestible but contin 35% or less of strch plus sugrs, compred to corn tht contins 75% strch. Severl experiments indicte tht when the sum of the strch plus sugrs is fed t levels bove.4% of body weight, the forge intke nd digestibility re reduced. In these situtions when forge is being supplemented, choosing highly digestible supplement such s soyben hulls compred to high strch supplement such s corn ppers to give 15 to 30% better performnce per unit of supplementl TDN. When compring the cost of TDN in these situtions, this suggests you cn py 15 to 30% more per unit of TDN nd still get the sme performnce. This is offered s guideline nd will depend on the sitution. Supplements contining nturl protein from sources such s cottonseed mel or soyben mel usully give better results thn supplements contining non-protein nitrogen (NPN) from sources such s ure. Growing cttle fed supplements contining NPN sources of crude protein usully hve better performnce thn heifers fed supplements with no dded protein when the TDN to crude protein rtio is over 7, but the performnce is often improved further when nturl protein sources re used. NPN supplements usully give performnce closer to nturl protein supplements when fed to hevier weight heifers nd when the supplements re fed t higher levels. A summry of 12 comprisons evluting the effects of feeding.20 to.36 lb/dy of rumen undegrded protein from fether, blood or corn gluten mels to growing cttle fed Florid wrm-seson perennil grss psture or hy showed tht gins were improved.32 lb/dy (Kunkle et l., 1994c). Selecting sources of energy nd protein tht provide the needed TDN nd protein t s low cost s possible is essentil. The lowest cost sources of nutrients will depend on the cost of ingredients, quntities purchsed, hndling nd storge system, processing nd mixing required, feeding system nd lbor vilble. The first decision is to nrrow the list of ingredients to those tht you cn use in your system, then compre prices bsed on the cost of the nutrients from ech source. A recent comprison of costs of TDN from severl sources shows rye psture, citrus pulp, nd whet midds to be some of the lower cost sources of TDN (Tble 5). A comprison of costs of protein shows tht cottonseed mel, whet middlings, corn gluten feed, nd whole cottonseed re some of the lower cost sources of protein (Tble 6). Limittions of ech feed must be considered. As n exmple, whole cottonseed should be limited to 5 lb/dy to void dirrhe cused by the high oil content. A complete minerl supplement should be fed long with the supplement. A complete minerl supplement contining slt, clcium phosphorus nd trce minerls is recommended. Minerl consumption vries cross pstures, sesons nd cttle, but n verge consumption of 2 ounces/dy of minerl contining 25% slt, 14 to 18% clcium, 8% phosphorus,.4% zinc,.2% iron,.2% mngnese,.15% copper,.016% iodine,.01% coblt nd.002% selenium hs been sufficient in mny situtions. Feeding 150 to 200 mg/dy of n ionophore such s Rumensin or Bovtec cn lso improve gins of growing cttle fed forge-bsed diets by.15 to.25 lb/dy. Another ntibiotic, Ginpro, is pproved for feeding t 10 to 20 mg/dy to cttle grzing psture. A summry of five trils evluting efficcy showed tht feeding 10 mg/dy of Ginpro improved gins.17 lb/dy nd feeding 20 mg/dy improved gins.23 lb/dy (Anonymous, 1994). Three psture feeding studies with growing cttle in Florid showed tht Ginpro incresed gins.22 lb/dy. These ntibiotics lter the fermenttion nd improve efficiency of feed use. These ntibiotics must be consumed regulrly to be effective. Mixing them into supplement is good wy to provide these ntibiotics. Cttle need to be fed these ntibiotics t lest every other dy to benefit. The ntibiotics improve gins of cttle on psture, but finding n effective nd economicl feeding system is often difficult. Mixing ionophores in minerl supplements often reduces consumption, or

4 Strtegies for Successful Development of Beef Heifers 4 consumption my be too spordic, which reduces the effectiveness of the ntibiotics. Ginpro mixed in minerl supplement does not pper to reduce minerl consumption, nd gins were incresed in severl studies, but designing minerl supplement tht will be consumed t consistent quntities cross different psture situtions remins formidble chllenge to this method of delivery. Dily feeding in crrier or protein supplement is often not cost effective unless other ingredients in the supplement increse importnce. Ginpro ppers to be sfe nd efficcious t dily intkes considerbly bove the pproved feeding level (10 to 20 mg/dy) nd does not pper to be toxic to other species t levels usully fed to cttle. Mngement Prewening The heifer weight t wening will determine the gin needed from wening to breeding. In some situtions, it my be more cost effective to increse gins before wening nd decrese needed post-wening gins. Creep feeding cn increse gins, but it should be used only when the weight is mostly muscle growth without significnt increse in ft. Reserch hs shown tht feeding high energy creep feed to smller frmed heifers will depress their subsequent milk production becuse of ft deposits in the developing udder (Ptterson et l., 1992). However, reserch with lrger frmed heifers showed no effect of creep feed on subsequent milk production. Therefore the decision to creep feed replcement heifers should consider the frme size nd fleshiness of the heifers. Limit feeding high protein creep feed such s cottonseed mel hs shown economicl increses in gins during the summer in Florid. Cottonseed mel mixed with 8 to 10% slt limited consumption to.65 lb/dy, improved gins.30 lb/dy nd required 2.2 lb of protein supplement for ech dditionl pound of gin t wening (Kunkle et l., 1993). Creep fed clves lso lern to et dry feeds, which cn reduce wening stress under some situtions. Creep feeding for 30 dys hs been shown to be sufficient to bunk brek clves nd reduce the stress of wening. The use of growth promoting implnts in suckling clves improves gins nd profits. Severl trils hve evluted the effect of prewening implnts on subsequent pregnncy rtes. A summry indicted tht implnting once between 1 nd 13 months showed no dverse effects on subsequent pregnncy rtes, implnting t or ner birth lowered pregnncy rtes nd multiple implnts re more likely to lower pregnncy rtes thn single implnts (Hrgrove, 1994). Therefore, selecting heifers tht hve received 1 implnt (fter 1 month) should improve wening weight with no dverse effect on pregnncy rte. Mngement - Wening to Breeding Selecting heifers t wening will determine the gins needed fter wening nd the likely success of clving the heifers t 2 yers of ge. Usully, lower percent of heifers with over 50% Brhmn will rech puberty nd become pregnnt during the breeding seson. Selecting heifers with higher wening weights will decrese the gin needed before the breeding seson. Selecting 15 to 50% more heifers thn needed for replcements will llow for the culling of those tht do not perform. Heifers need to be kept seprte from the cow herd nd, if vrible in wening weight, it is often desirble to divide them into light nd hevy weight groups. The light weight group cn be fed dditionl supplement to rech the trget weight by the beginning of the breeding seson. This should improve the percent pregnnt nd be cost effective (Wiltbnk, 1994). The stress of wening often results in sickness nd low gins fter wening. A complete herd helth progrm with pproprite vccintions nd prsite control prior to nd t wening cn help reduce these losses (Richey, 1994). The first month fter wening is criticl to meeting the trget weights t breeding. Reducing wening stress nd sickness nd keeping the heifers gining weight is essentil. This usully requires tht heifers strt eting supplements within week fter wening. Psturing the cttle on freshly regrown psture cn be helpful, but feeding very pltble supplement such s commercil preconditioning supplement hs proven successful for mny producers. Creep feeding the clves usully improves the consumption of feed immeditely fter wening, helping to reduce stress.

5 Strtegies for Successful Development of Beef Heifers 5 Any supplementtion progrm needs to be monitored nd supplements djusted depending on the conditions. A few representtive heifers should be weighed every 2 months nd the feeding progrm djusted to rech the trget weights. Mny rnchers use winter psture to grow heifers, but typiclly winter pstures re not redy to grze for 2 to 3 months fter wening. In this progrm, heifers re often not given much supplement before grzing winter psture nd my gin.5 lb/dy or less. While grzing winter psture, the heifers usully compenste nd my rech the trget weight by the beginning of breeding seson. Mrshll (1991) compred progrm with continuous gin from wening to breeding to progrm with low gins for 2 to 3 months followed by rpid gins (low-rpid) to chieve the sme weight t the strt of the breeding seson for both groups. Pregnncy rtes were similr for both groups, but heifers on the low-rpid growth progrm conceived lter in the breeding seson thn heifers tht gined continuously from wening to breeding. This would be expected to lower the wening weights of their clves nd reduce the percent of the cows tht will rebreed. Therefore, better results cn be expected if heifers re fed to gin weight nd not get thin during the fll before grzing winter psture. Another mngement strtegy tht producers my wnt to consider to increse the number of heifers reching puberty is exposing them to ltered or sterile bulls before the breeding seson. In Nebrsk reserch, heifers exposed to bull reched puberty 40 dys erlier with 50% pregnnt in the first 21 dys of the breeding seson compred to 16.5% pregnnt for heifers not exposed to the bull (Kinder et l., 1994). Breeding heifers to clve 3 to 4 weeks before the cow herd is desirble to improve their rebreeding. First-clf heifers usully require 2 to 3 weeks longer to come into estrus thn older cows, nd clving erlier helps keep the heifers clving with the herd. A smll pelvic opening hs been shown to increse the chnces of clving difficulty (Wiltbnk, 1994). If extr heifers re kept, culling those with smll pelvic re (less thn 190 squre centimeters t pregnncy testing) my reduce clving difficulties nd clf deths. Mngement t Breeding Reching the trget weight of 65% of mture weight t the beginning of the breeding seson is essentil. Heifers should be fed to gin pproximtely 1 lb/dy during the breeding seson. A breeding seson shorter thn tht used in the cow herd is suggested. As n exmple, if 90 dy breeding seson is used in the cow herd, then 60 dy breeding seson (strting before or t the sme time s the breeding seson for the cow herd) is suggested for the heifers. This llows the heifer extr time fter her first clf for rebreeding. Selecting bulls to reduce clving difficulty or dystoci is essentil. The breed of bull nd the bulls within the breed need to be selected to reduce problems t clving. Severl breeds of cttle offer Expected Progeny Difference (EPD) estimtes for bulls. Selecting bulls with low EPD for birth weight cn help reduce dystoci (Brinks, 1994; Bellows nd Stigmiller, 1994). The dded lbor of ssisting heifers, clf deths, heifer deths nd lower percent of heifers rebreeding fter difficult births mke this priority in selecting bulls to use on first-clf heifers. Estrus synchroniztion is nother technique tht my help increse the number of heifers tht breed erly in the clving seson. Melengesterol cette (MGA)-Prostglndin (PG) nd Synchromte B (SMB, currently unvilble) hve been shown to induce erlier estrus in heifers tht re close to inititing estrus (Short et l., 1994b; Odde nd Hollnd, 1994). In Florid studies, feeding.5 mg/dy of MGA for 14 dys followed 16 dys lter with n injection of prostglndin resulted in n 8 to 9% higher pregnncy rte compred to untreted cttle. These estrus synchroniztion progrms cn be used with rtificil insemintion or breeding with bulls. Mngement - Breeding to Clving Mnging the heifers to rech 85% or more of their mture weight t clving is recommended. Body condition score (BCS) is more importnt thn weight, nd BCS of 6 is recommended t clving (Wettemn, 1994). BCS is closely relted to the rebreeding nd is much esier to monitor thn weight. During the lst 3 months of pregnncy, the clf grows considerbly, nd cows my gin weight but loose

6 Strtegies for Successful Development of Beef Heifers 6 BCS; therefore, monitoring BCS is n importnt indictor of nutrition in the heifer. The supplementl feed needed will depend on the forges nd the month of the yer. Grzing heifers on the better pstures will often provide sufficient nutrition for dequte gin nd good body condition. Supplements contining minerls nd growth-promoting ntibiotics cn increse gins, nd protein supplements my improve gins under some conditions. Mngement - Clving through Rebreeding Heifers should be mnged s seprte group or mnged where they cn be observed closely t clving. Clving difficulties re more common in heifers nd frequent observtion cn increse the number of live clves nd hopefully void heifer deths. Good fcilities re needed to mnge cttle t clving. Heifers cn lose weight nd BCS very rpidly fter clving becuse nutritionl requirements increse drmticlly. Rebreeding is closely relted to the body condition t clving nd weight loss fter clving (Kunkle et l., 1994, 1994b). If heifers clve erly in the clving seson in BCS 6, then moderte weight loss up to.5 lb/dy will usully result in good pregnncy rtes. Results of severl rnch trils showed tht first- or second-clf cows in BCS 5 or higher t pregnncy testing hd pregnncy rtes of 84% or higher compred to 53% for young cows in BCS 4 nd less thn 24% for BCS 3 (Tble 7). Clving young cows in good body condition nd mintining this body condition is essentil for good pregnncy rtes. Heifers hve higher protein requirements fter clving thn mture cows. Studies t the On Reserch Center hve shown drmtic improvements in rebreeding of heifers supplemented with protein (Pte et l., 1990). Heifers in these studies were in BCS 5 to 6 t clving but lost 1 to 1.5 BCS by the beginning of breeding seson. Heifers were fed low qulity hy nd those supplemented with molsses (no dded protein) hd 38% pregnncy rte, heifers supplemented with molsses-ure hd 60% pregnncy rte nd those supplemented with molsses-cottonseed mel hd 70% pregnncy rte. Protein supplements did not improve the pregnncy rtes of mture cows. These studies nd others indicte tht feeding dequte levels of protein to heifers is criticl to hve good reproductive performnce. Rebreeding heifers nd cows my be delyed in some situtions, especilly when cows re in mrginl BCS nd nutrition. Clf removl for 48 hours t 40 to 80 dys fter clving hs been effective in inititing estrus in some cows (Wiltbnk, 1994; Odde nd Hollnd, 1994). This technique is most effective when cows re close to inititing estrus but is not usully effective in cows tht re in good flesh, (BCS 5 or more) or very thin (BCS 3 or less). The interruption of suckling for 48 hours ppers to trigger the initition of estrus. Most cows will still own their clves fter the 48 hours of clf sepertion, nd this hs not reduced wening weights. This mngement technique my be useful for cows in BCS 4 if they re not inititing estrus nd if good fcilities re vilble for 48-hour clf removl. Other Fctors A good mngement progrm must include good helth progrm. Diseses nd prsites cn reduce cttle gins nd reduce the clf crop. A miniml disese control progrm includes n effective vccintion progrm for brucellosis, leptospirosis nd vibriosis. Additionl diseses tht my reduce performnce include 1BR, BVD, PI3, BRSV, Hemophilus Somnus, Psteurell nd Trichomonisis (Richey, 1994). A control progrm for intestinl worms, flukes, horn flies nd lice is needed. A comprehensive niml helth mngement progrm developed in consulttion with your veterinrin is essentil. The bull must be cpble of breeding heifers nd cows. Selection of bulls with dequte scrotl circumference nd clving ese ws discussed previously. Bulls must lso be fertile, cpble of inseminting cow nd hve the desire to breed cows. An nnul evlution of bulls for breeding soundness is recommended (Chenoweth, 1994). Libido testing of bulls to evlute their desire to breed cows cn be useful in some situtions.

7 Strtegies for Successful Development of Beef Heifers 7 References Anonymous Ginpro Resource Mnul. Hoechst-Roussel Agri-Vet Compny, Somerville, NJ. Bellows, R.A. nd R.B. Stigmiller Selection for fertility. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Brinks, J.S Reltionships of scrotl circumference nd subsequent reproductive performnce in mle nd femle offspring. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Chenoweth, P.J Bull behvior, sex-drive nd mngement. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Hrgrove, D.D Use of growth promotnts in replcement heifers. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Kinder, J.E., M.S. Roberson, M.W. Wolfe nd T.T. Stumpf Mngement fctors ffecting puberty in the heifer. In: Fctors Affecting the Clf Crop, pp 69-89, CRC Press, Boc Rton, Florid. Kunkle, W.E., P. Hogue, E. Jennings nd S. Sumner Protein supplement my improve gins of nursing clves. Animl Science Fct Sheet SS-ANS-11, 2 pp, Univ. of Florid. Kunkle, W.E., R.S. Snd nd D.O. Re Effects of body condition on productivity in beef cttle. Fl. Coop. Ext. Service SP 144, 13 pp. (circulr). Kunkle, W.E., R.S. Snd nd P. Grces-Yepez Applying new strtegies for rising beef heifers. Fl. Ruminnt Nutr. Symposium, pp Kunkle, W.E., R.S. Snd nd D.O. Re. 1994b. Effect of body condition score on productivity in beef cttle. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Kunkle, W.E., D.A. Stteler, D.B. Btes, L.M. Rutter, W.F. Brown nd F.M. Pte. 1994c. Protein levels nd sources in molsses for growing cttle. Fl. Ruminnt Nutr. Symposium, pp Mrshll, T.T Mnging heifers in Florid to clve first t two yers of ge. Proc. Beef Cttle Shortcourse, pp , Univ. of Florid. NRC, Nutrient Requirements of Beef Cttle (6 th Rev. Ed.). Ntionl Acdemy Press, Wshington, DC. Odde, M.K. nd M. D. Hollnd Synchroniztion of estrus in cttle. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Pte, F.M., S.W. Snson nd R.V. Mchen, Vlue of molsses mixture contining nturl protein s supplement to brood cows offered low-qulity forges. J. Animl Sci. 68:618:623. Ptterson, D.J., R.C. Perry, G.H. Kircofe, R.A. Bellows, R.B. Stigmiller nd L.R. Corh Mngement considertions in heifer development nd puberty. J. Anim. Sci. 70: Re, D.O., W.E. Kunkle, P.J. Chenoweth nd R.S. Snd Reltionship of prity nd body condition score to pregnncy rtes in Florid beef cttle. Theriogenology 39: Rndel, R.D Unique reproductive trits of Brhmn nd Brhmn bsed cows. In: Fctors Affecting the Clf Crop, pp 23-44, CRC Press, Boc Rton, Florid. Richey, E.J Keep herd helth simple nd mke it fit the beef cttle opertion. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Short, R.E., R.B. Stigmiller, R.A. Bellows, D.C. Adms nd J.G. Berrdinelli Effects of suckling on postprtum reproduction. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Short, R.E., R.B. Stigmiller, R.A. Bellows nd R.C. Greer. 1994b. Breeding heifers t one yer of

8 Strtegies for Successful Development of Beef Heifers 8 ge: biologicl nd economic considertions. In: Fctors Affecting the Clf Crop, pp 55-68, CRC Press, Boc Rton, Florid. Wettemn, R.P Mngement of nutritionl fctors ffecting the preprtum nd postprtum cow. In: Fctors Affecting the Clf Crop, pp , CRC Press, Boc Rton, Florid. Wiltbnk, J.N Chllenges for improving clf crop. In: Fctors Affecting the Clf Crop, pp 1-22, CRC Press, Boc Rton, Florid.

9 Strtegies for Successful Development of Beef Heifers 9 Tble 1. Trget Weights for Growing nd Breeding Heifers to Clve t Two Yers of Age (1000 lb Mture Cow Weights). Weight (lb) Dte Dys Begin Ending Dily Gin (lb) Comments 9/15-3/ Wen to Breeding 3/15-5/ Breeding Seson 5/15-12/ Grow but not ftten 12/15-4/ Clving - no flesh loss 4/1-6/ Rebreeding in 90 dys Tble 2. Dily TDN nd Protein Requirements of Heifers t Vrious Weights nd Gins. Weight (lb) Dily Gin (lb) Dry Mtter Intke (lb/dy) TDN Crude Protein lb/dy % lb/dy % Nutrient Requirements of Beef Cttle, Ntionl Reserch Council, Tble 3. Dily Levels of 75% TDN Supplement Required For Vrious Gins of 600 lb Heifers Fed Different Qulity Forges. Forge QI=1.0 b Forge QI=1.2 c Forge QI=1.4 d Gin Level e Protein f Level e Protein f Level e Protein f lb lb % lb % lb % Qulity Index (QI) = TDN intke s multiple of mintennce (1.0 = mintennce). b QI=1.0, TDN=47%, Crude protein=6%. c QI=1.2, TDN=54%, Crude protein=9%. d QI=1.4, TDN=58%, Crude protein=12%. e Supplement (lb/dy) needed long with forge vilble d libitum. f Crude protein (%) needed in 75% TDN supplement to meet requirements of 600 lb heifer.

10 Strtegies for Successful Development of Beef Heifers 10 Tble 4. Corn, whet middlings (WM), nd soyben hull (SH) supplements for growing cttle fed bermudgrss hy. Supplements Low-25% TDN High-50% TDN None Corn WM SH Corn WM SH Dily gin, lb BCS chnge b Intke, % BW Supplement Hy Totl Digestibility, % Orgnic mtter NDF c Kunkle et l., b Body condition score chnge. c Neutrl detergent fiber. Tble 5. Nutrient Composition nd Costs of Energy Supplements. Feed TDN (% s fed) Crude Protein (% s fed) Cost ($/unit) Cost of TDN b ($/100 lb) Hy, round bles /1000 lb 5.21 Sorghum silge (30% DM) 18(60) 2(7) 18/ton 5.00 Shelled corn bulk, 25 ton /ton 5.94 bgged, 50 lb /50 lb Hominy /ton 5.42 Citrus pulp /ton 4.56 Whet midds /ton 4.45 Corn gluten feed /ton 5.41 Soyben hulls, 25 ton /ton 6.07 Blckstrp molsses, 25 ton /ton 7.18 Liquid supplement-16% CP bulk, 25 ton /ton delivered to lick tnk /ton Steer grower-12% /50 lb Whole cottonseed, bulk-25 ton /ton 7.82 Rye psture /cre Prices quoted during Fll 2000 from suppliers in centrl Florid, prices vry in different res of the stte nd with different quntities purchsed. b Cost of TDN ($/100 lb) is clculted by dividing the cost of 100 pounds of feed by the TDN frction (% TDN/100). Exmple for hy - $25/1000 lb=$2.50/100 lb (25/10); 100 lb of hy contins 48 lb TDN nd 100 lb TDN costs $5.21 (2.50/.48).

11 Strtegies for Successful Development of Beef Heifers 11 Tble 6. Nutrient Composition nd Costs of Protein Supplements. Feed Soyben mel Crude Protein (% s fed) TDN (% s fed) Cost ($/unit) Cost of Protein b ($/100 lb) bulk, 25 ton /ton bgged, 50 lb /50 lb Cottonseed mel bulk, 25 ton /ton bgged, 50 lb /50 lb Whet middlings, 25 ton bulk /ton Corn gluten feed, 25 ton bulk /ton Rnge cubes /50 lb Protein block, 33 lb /33 lb Molsses blocks 200 lb /200 lb lb /500 lb Liquid supplement, 16% CP bulk, 25 ton /ton delivered to lick tnk /ton Liquid supplement, 32% CP bulk, 25 ton /ton delivered to lick tnk /ton Whole cottonseed, 25 ton /ton Prices quoted during Fll 2000 from suppliers in centrl Florid, prices vry in different res of the stte nd with different quntities purchsed. b Cost of protein ($/100 lb) is clculted by dividing the cost of 100 lb of feed by the protein frction (% protein/100). Exmple for soyben mel - $210./ton=$10.50/100 lb (210/20); 100 lb of soyben mel contins 48 lb protein nd 100 lb protein costs $21.88 (10.50/.48). Tble 7. Reltionship of Prity nd Body Condition Score to Pregnncy Rte, %. Prity b Body Condition Score c All <3 4 > > All Re et l., 1993; Body condition scored t pregnncy testing. b Prity is the number of clving opportunities, present ge minus ge t first clving (yers). c Body condition scored t pregnncy testing from 1 to 9, 3=thin, 4=borderline, 5=moderte.