Renquist B J, Oltjen J W, Sainz R D, Calvert C C
Department of Animal Science, University of California, Davis 95616, USA.
J Anim Sci. 2006 Jul;84(7):1890-5. doi: 10.2527/jas.2005-733.
Pregnancy rate, calving interval, birth weight, weaning weight, and quarterly BCS were collected for 5 consecutive years on 454 fall-calving multiparous British crossbred cattle (3 to 10 yr of age) to evaluate associations of age with BCS and production parameters. Body weight and BCS were collected pre-calving, prebreeding, at weaning, and midway through the second trimester of pregnancy (August). Body condition score was correlated with age during all seasons (P < 0.01). At calving, breeding, and in August, 3-yr-old cows had the lowest BW and BCS, whereas 8-yr-old cows had the greatest. At weaning, these values were maximal in 10-yr-old cows. Pregnancy rate was near 80% up to 9 yr of age but decreased to 57% in 10-yr-old cows. The relationship of pregnancy rate with age appears to be correlated with the BCS decrease at breeding in the older cows, supported by the fact that inclusion of BCS at breeding in the statistical model eliminated the effect of age on pregnancy rate (P = 0.42). Calving interval was longer in 3-yr-old cows compared with 4- to 9-yr-old cows (P = 0.02); however, among older cows, there was little change in the calving interval. Birth weight reached a maximum at 8 yr of age (35 +/- 0.9 kg) and a minimum in 3-yr-old cows (32 +/- 0.7 kg). Birth weights of calves born to both 3- and 4-yr-old cows were lower than for those born to 5-, 6-, 7-, or 8-yr-old cows (P < 0.05). Ten-year-old cows weaned lighter calves (205-d adjusted weaning weight) than younger dams. Furthermore, 3-yr-old cows weaned calves 9 +/- 2.1 and 14 +/- 2.4 kg lighter than 4- and 5-yr-old cows, respectively (P < 0.001). Interpretation of the age analyses of calving interval, birth weight, and weaning weight was independent of the inclusion of BCS in the model. This study documents the effects of age on calving interval, birth weight, and weaning weight that are independent of BCS.
连续5年收集了454头秋季产犊的经产英国杂交母牛（3至10岁）的妊娠率、产犊间隔、出生体重、断奶体重和季度体况评分（BCS），以评估年龄与BCS和生产参数之间的关联。在产犊前、配种前、断奶时以及妊娠中期（8月）收集体重和BCS。所有季节的体况评分均与年龄相关（P < 0.01）。在产犊、配种时和8月，3岁母牛的体重和BCS最低，而8岁母牛的体重和BCS最高。在断奶时，这些值在10岁母牛中最大。9岁及以下母牛的妊娠率接近80%，但10岁母牛的妊娠率降至57%。妊娠率与年龄的关系似乎与年长母牛配种时BCS的下降有关，这一事实得到了支持，即在统计模型中纳入配种时的BCS消除了年龄对妊娠率的影响（P = 0.42）。与4至9岁母牛相比，3岁母牛的产犊间隔更长（P = 0.02）；然而，在年长母牛中，产犊间隔变化不大。出生体重在8岁时达到最大值（35±0.9千克），在3岁母牛中达到最小值（32±0.7千克）。3岁和4岁母牛所产犊牛的出生体重低于5岁、6岁、7岁或8岁母牛所产犊牛（P < 0.05）。10岁母牛断奶的犊牛（205天校正断奶体重）比年轻母牛的犊牛轻。此外，3岁母牛断奶的犊牛分别比4岁和5岁母牛断奶的犊牛轻9±2.1千克和14±2.4千克（P < 0.001）。产犊间隔、出生体重和断奶体重的年龄分析结果不受模型中是否纳入BCS的影响。本研究记录了年龄对产犊间隔、出生体重和断奶体重的影响，这些影响与BCS无关。
