Impact of Body Condition at Calving on Reproductive Productivity in Beef Cattle

Transcription

1 Impct of Body Condition t Clving on Reproductive Productivity in Beef Cttle Allen Bridges - Extension Specilist, Reproduction, Dept. Anim. Sci., Purdue University Ron Lemenger Extension Beef Specilist, Dept. Anim. Sci., Purdue University Overview: A lte spring frost nd hot dry summer experienced in much of the Midwest left mny beef producers with less vilble stored feed for the winter months. Additionlly, much of the stored forge is of low qulity nd includes lterntive forge sources such s bled corn stlks nd soyben strw. Given this scenrio, without proper mngement, there is the potentil tht the nutritionl requirements for lte gestting nd erly lctting cows will not be met, resulting in loss of body condition prior to clving nd the spring breeding seson. With the incresed costs of buying dditionl hy or providing feed supplement, producers might be tempted to just get by which would result in cows losing body condition during the winter. However, such decision, or lck of ction, will in fct be more costly in the long run. Reproductive performnce is gretly impcted by totl body energy reserves (body condition) t specific times during the production cycle. If cows re thin t clving, reproductive performnce in the subsequent breeding seson will suffer, resulting in reduced yerly profits per cows. Therefore, to optimize reproductive performnce next spring, producers my need to consider winter supplementtion strtegies tht meet the nutritionl requirements of their cow herd nd ensure optiml breeding performnce this spring. Impct of Body Condition on Reproduction: Numerous reserch studies hve indicted tht under-nutrition due to limited feed vilbility or poor-qulity feed sources during lte gesttion (preprtum) nd/or erly lcttion (postprtum) hs detrimentl effects on subsequent reproductive efficiency. Reproductive performnce is closely linked to the mount of vilble energy reserves cow hs which is reflected by her mount of body ft. The most prcticl method to estimte the energy reserves of cows is by evluting the proportion of body ft vi body condition scoring (BCS). BCS re bsed on numeric scle of 1 to 9, with cows with 1 being extremely thin nd 9 being obese. For more informtion of how to ccurtely ssign BCS plese view the Purdue University Extension video t the following web ddress: It is importnt to evlute the BCS of your cow herd t lest monthly to determine if cows re losing or gining body condition. This will llow you to djust your nutritionl mngement ccordingly during the preprtum nd postprtum periods. For optiml reproductive performnce during the subsequent breeding seson, mture cows should be BCS of 5 to 5.5 nd first clf heifers should hve BCS of 5.5 to 6 t clving nd through the breeding seson.

2 Tble 1. Net energy of mintennce (NE m ; Mcl/d) nd crude protein (CP; lb/d) requirement of 1200 lb cow during gesttion nd erly lcttion. NE m (Mcl/d) b CP (lb/d) c Mid-Gesttion Lte Gesttion Erly Lcttion (10 lbs milk/d) Erly Lcttion (20 lbs milk/d) Adpted from the NRC, Nutrient Requirements of Beef Cttle. b Dily energy (Mcl/d) required for mintennce. c Dily crude protein required for mintennce. Frequently ssessing BCS in the winter is criticl s this time corresponds to the third trimester of pregnncy for most spring clving herds. As pregnncy proceeds, the nutritionl requirement for both net energy nd crude protein increse to support fetl nd plcentl growth (Tble 1). Environmentl stressors such s extreme cold, wind chill nd/or wet wether further dd to the nutritionl requirements of the beef herd. If intke of energy nd/or protein is below tht required to meet the cow s needs for mintennce, pregnncy or lcttion, nd environmentl stress, cows will try to compenste by mobilizing stored energy (body ft) nd will therefore lose body condition. Following clving, the nutritionl requirements gin increse to support lcttion nd repir of the reproductive trct. Therefore, if cows re thin t clving, due to sub-mintennce energy intke during lte gesttion, the incresed demnd for energy nd protein to support lcttion will mke it even more difficult nd expensive to djust body condition between clving nd the beginning of the breeding seson. Therefore, it is criticl tht the body condition monitored nd djusted prior to clving to ensure tht dequte nutrition is delivered nd tht cows re in proper condition by clving. If cows re thin prior to clving, supplementtion is necessry to regin body condition. Tble 2. Weight gins needed in mture cows to chieve proper BCS t clving. Body Condition Weight Gin Needed At Wening Needed t Clving Fetus & Plcent (lb) Body Wt b (lb) Totl Wt b (lb) Dys to Clving ADG c Adpted from Wiltbnk, 1982 b WT = Weight c Averge Dily Gin needed cross the scle to support fetl growth nd BCS chnge. As generl rule of thumb, it will tke 80 lbs of body weight gin for mture cow nd 150 lbs of gin for first clf heifer to gin 1 BCS. However, this

3 estimte does not tke into ccount the dditionl nutritionl requirements needed to support the dvncing pregnncy. As illustrted in Tble 2, the mount of BCS needed to be gined nd the time vilble between wening nd clving will dictte the ggressiveness of the nutritionl progrm. Providing dditionl nutrients during this period cn increse costs; however this dditionl nutrition is needed to ensure optiml reproductive performnce. Feed costs cn be reduced following the breeding seson, once the cows conceive. Filing to chieve n dequte BCS t clving cn negtively impct vrious spects of reproductive performnce. A mjor constrint to reproductive efficiency in beef herd is the durtion between clving nd the resumption of norml estrous cycles nd ovultion, referred to s the postprtum intervl. To mintin 12-month clving intervl, cow must conceive within 80 to 85 dys of clving. If the intervl from clving until resumption of norml estrous cycles is extended pst 85 dys the clving intervl will be extended s well. Filing to mintin cows in pproprite body condition results in n extended period of postprtum nestrus nd Tble 3. Effect of body condition score (BCS) t clving on postprtum intervl. BCS Postprtum Intervl b Adpted from Houghton et l., 1990 Purdue University b Averge dy post-clving when cows resumed norml estrous cycles Tble 4. BCS t clving nd percent of cows tht hve shown estrus fter clving. % Shown Estrus BCS t Clving Number Cows 60 dys postclving 90 dys postclving Thin ( 4) Good (5-6) Ft ( 7) Adpted from Whitmn, 1975 Colordo Stte University n extended postprtum intervl. This is illustrted in Tble 3 nd 4. In Tble 3, s BCS t clving decreses, postprtum intervl increses. Dt in Tble 4 demonstrtes tht if cows re thin (BCS 4) t clving, only two-thirds will hve resumed norml estrous cycles by 90 dy post-clving. Collectively these dt clerly demonstrte tht thin cows tke longer to exhibit estrus following clving resulting in n extended clving intervl nd filure to chieve one clf per cow every 12 months. Moreover, n extended

4 postprtum intervl due to indequte body condition lso results in fewer cows returning to estrus during the breeding seson, ultimtely resulting in fewer cows getting rebred. This is illustrted in Figure 1, which shows the percentge of cows tht were rebred in six reserch herds (four sttes) nd includes both mture nd young cows. These dt clerly indicte tht BCS t clving considerbly influences the percentge of cows getting rebred in the subsequent 60 to 90 dy breeding seson. These dt nd numerous other dt sets conclusively show tht cows in poor body condition t clving hve poorer reproductive performnce in the subsequent breeding 100 seson. To increse the likelihood of successful 80 pregnncy some producers my consider incresing the length of the breeding seson for cows 40 tht re in poor body condition. 20 This is not recommended s cows in poor body condition 0 will not rebreed t cceptble levels unless the cows re hevily supplemented during the breeding seson to increse body ft reserves. Extending the breeding seson will lso result in lower milk production, smller/lighter clves t wening, nd extended clving intervl the next yer, which further reduces the likelihood the cows will rebred next yer. % Rebred < 4 5 > 6 Body Condition Score Figure 1. Percent of cows rebred in the subsequent breeding seson ccording to BCS t clving (summry of six trils in 4 sttes). Adpted from G. Selk, Oklhom Stte Univer. Oklhom Coopertive Extension Service Publiction ANSI In ddition to poor reproductive performnce of the beef cow, body condition lso ffects the performnce of her clf. Cows in poor body condition t clving hve smller clves tht re weker nd more susceptible to disese. Thin cows hve both lower qulity nd quntity of colostrums nd produce less milk during lcttion. These fctors together result in reduced wening weights of clves from thin cows. Furthermore, thin cows tht get pregnnt following n extended postprtum intervl will hve clves tht re younger nd smller t wening the following yer. Tking into ccount the problems ssocited with thin cows t clving, s outlined bove, the economic rmifictions cn be substntil. The impct tht BCS t clving hs on reproductive efficiency, clf performnce, nd frm income is presented in Tble 5. Thin cows (BCS 3 nd 4) hve reduced pregnncy rtes, incresed clving intervls, wen younger/lighter clf, nd provide considerbly less yerly income compred to cows tht re in good condition (BCS 5 nd 6) t clving. The income per cow is reduced by over $140 when BCS decreses from 5 to 4. Therefore, the extr expense of supplementl feeds during the winter months is recptured in the yerly profitbility of the cows. The improvement in reproductive efficiency of cows mintined in good body condition is

5 substntil, however, level of incresed income (profitbility) from improving BCS will vry depending upon severl fctors, most notbly feed costs. Tble 5. Reltionship of body condition score (BCS) to beef cow performnce nd income. Summry Preg. Rte, % c Clving Intervl, dys Optiml reproductive performnce of your cow herd requires tht cows be in BCS of 5 or better t clving nd through the breeding seson. Economiclly, spending dditionl dollrs during the winter to mintin cows in good body condition will result in incresed vlue of your cow herd. However, given the shortge of forge nd stored feed vilble this winter, mintining cows in good body condition will be chllenging. Suggested feeding strtegies for producers with limited feed supplies re vilble under the publictions link t: For dditionl informtion contct: Allen Bridges, Ph.D. Deprtment of Animl Sciences Purdue University 915 W. Stte St. West Lfyette, IN (765) llenbridges@purdue.edu WA, dys d DG, lb e WW, lb f Price $/100 lb g Yerly Income $/Cow i Income BCS b $/ h Adpted from Kunkle et l., 1998 UF/IFAS Publiction SP-144 b Body Condition Score: scle of 1 (thin) to 9 (obese) c Pregnncy rtes verged cross trils in Texs, Oklhom, nd Florid when BCS ws ssessed t clving, breeding, nd pregnncy testing. d Wening Age; 240 dys for cows in BCS of 5 nd 6 nd decreses s clving intervls increse. e Averge Dily Gin f Adjusted Wening Weight; clculted s clf ge times clf gin plus birth weight (70 lb). g Averge price for similr weight clves during December of h Clculted s clf weight times clf price. i Clculted s income/clf times pregnncy rte times 0.92 (% clves rised of those pregnnt).

6 References: Houghton, PL, RP Lemenger, LA Horstmn, KS Hendrix, nd GE Moss Effects of body composition, pre- nd postprtum energy level nd erly wening on reproductive performnce of beef cows nd prewening clf gin. J. Anim. Sci. 68:1438. Kunkle, WE, RS Snds, nd DO Re Effects of body condition on productivity in beef cttle. Deprtment of Animl Sciences, Florid Coopertive Extension Service, UF/IFAS. SP-144. Rndel, RD Nutrition nd postprtum rebreeding in cttle. J. Anim. Sci. 68:853. Rossi, J nd TW Wilson Body condition scoring beef cows. The University of Georgi Coopertive Extension, Bulletin G. Selk. Body condition scoring of beef cows. Oklhom Stte University. Oklhom Coopertive Extension Service Publiction ANSI Whitmn, RW Weight chnge, body condition nd beef-cow reproduction. Ph.D. Disserttion, Colordo Stte University. Wiltbnk, JN Nutrition nd reproduction in the beef femle. Proc. Symposium on Mngement of Food Producing Animls, pp