Morrison D G, Spitzer J C, Perkins J L
Louisiana State University Agricultural Center, Rosepine Research Station, 70659, USA.
J Anim Sci. 1999 May;77(5):1048-54. doi: 10.2527/1999.7751048x.
Multiparous, spring-calving beef cows (n = 250) were used to determine whether large changes in body energy reserves during mid- to late gestation influenced subsequent reproductive performance of cows calving in moderate body condition. In three states, cows were blocked by BW and body condition score (BCS; 1 = emaciated to 9 = obese) then allotted to receive either a high or low plane of nutrition from late summer to early winter over a 3-yr period. This generated an array of BCS by the beginning of the last trimester of pregnancy when cows were grouped by BCS as follows: Group 1, BCS < or = 4; Group 2, BCS of 5 or 6; and Group 3, BCS > or = 7. Each group was managed so that individual cows would calve with a BCS of 5 to 6. At the time of group assignment, mean BW and BCS differed (P < .01) among groups and were 480 kg and 3.6, 541 kg and 5.5, and 594 kg and 7.1 for Groups 1 to 3, respectively. Within 28 d before calving, BW and BCS were similar (P > .20) among groups averaging 555 kg and 5.1. Prepartum BCS changes averaged 1.4, -.4, and -2.0 units for Groups 1 to 3, respectively (P < .01). Cows were managed as a single group after calving in each state. Location effect was significant for the prepartum and postpartum BW and BCS changes but not for postpartum reproductive performance. Significant location x BCS group interactions were found for the 90-d prepartum BW, BCS at calving, and prepartum changes in BW, but were caused by differences in magnitude among locations. The percentage of cows with luteal activity at the start of a subsequent breeding season was not affected (P > .20) by either location or BCS group, and averaged 66%. Mean pregnancy rates at 20, 40, and 60 d of a subsequent breeding season were 55, 76, and 89% for Group 1; 51, 67, and 82% for Group 2; and 64, 79, and 89% for Group 3 (P > .30). Mean days to conception were 89, 87, and 85 for Groups 1 to 3, respectively (P = .70). Neither calf birth weight (x = 38.6 kg) nor adjusted 205-d weight (x = 223.6 kg) were affected by prepartum BW and BCS changes. We conclude that reproductive performance of cows calving in moderate body condition is not influenced by large changes in body energy reserves during the last trimester of pregnancy.
选用经产、春季产犊的肉用母牛（n = 250）来确定妊娠中后期体能量储备的大幅变化是否会影响体况适中的产犊母牛随后的繁殖性能。在三个州，根据体重（BW）和体况评分（BCS；1 = 消瘦至9 = 肥胖）对母牛进行分组，然后在3年期间从夏末到初冬将其分配接受高营养水平或低营养水平的饲养。到妊娠最后三个月开始时，由此产生了一系列体况评分，此时根据体况评分将母牛分为以下几组：第1组，BCS≤4；第2组，BCS为5或6；第3组，BCS≥7。对每组进行管理，使个体母牛产犊时的体况评分为5至6。在分组时，各组间的平均体重和体况评分存在差异（P < 0.01），第1至3组分别为480千克和3.6、541千克和5.5、594千克和7.1。在产犊前28天内，各组间的体重和体况评分相似（P > 0.20），平均为555千克和5.1。第1至3组产犊前体况评分的变化平均分别为1.4、 -0.4和 -2.0个单位（P < 0.01）。在每个州，母牛产犊后作为一个单一群体进行管理。产犊前和产后体重及体况评分的变化存在显著的地点效应，但对产后繁殖性能没有影响。在产犊前90天的体重、产犊时的体况评分以及体重的产犊前变化方面发现了显著的地点×体况评分组交互作用，但这是由不同地点间幅度差异引起的。随后繁殖季节开始时具有黄体活性的母牛百分比不受地点或体况评分组的影响（P > 0.20），平均为66%。在随后繁殖季节的第20、40和60天，第1组的平均妊娠率分别为55%、76%和89%；第2组为51%、67%和82%；第3组为64%、79%和89%（P > 0.30）。第1至3组的平均受孕天数分别为89天、87天和85天（P = 0.70）。犊牛出生体重（x = 38.6千克）和调整后的205天体重（x =
