Hageman W H, Shook G E, Tyler W J
Department of Dairy Science, University of Wisconsin-Madison 53706.
J Dairy Sci. 1991 Dec;74(12):4366-76. doi: 10.3168/jds.S0022-0302(91)78633-5.
Genetic lines were created by selection of service sires differing by approximately 450 kg of milk for estimated transmitting ability. High line sires were selected from the best available proven sires. Selection continued over 24 yr with up to eight generations of selection. Records from 708 nulliparous, 575 first parity, and 437 second parity animals were analyzed. High milk yield was associated with longer days open and calving intervals in both first and second parities. A 1000-kg increase in 305-d milk production was associated with average increases in both days open and calving interval of around 7 d in first parity and 13 d in second parity and with average increases in days to first detected estrus of 4.5 d in first parity. Difference between genetic lines for milk yield was 804 kg in first parity and 772 kg in second parity. Days open and calving interval were less for the average line in both parities and differed by 10 d in second parity. Other reproductive differences were small or insignificant. Selection for yield has affected reproductive fitness modestly.
通过选择预计传递能力相差约450千克牛奶的种公牛来培育遗传品系。高产品系的种公牛从现有的最佳经证实的种公牛中挑选。选择持续了24年，进行了多达八代的选择。分析了708头未产母牛、575头头胎母牛和437头二胎母牛的记录。高牛奶产量与头胎和二胎的较长空怀天数和产犊间隔有关。305天牛奶产量增加1000千克，头胎空怀天数和产犊间隔平均增加约7天，二胎增加13天，头胎首次检测到发情的天数平均增加4.5天。头胎牛奶产量的遗传品系差异为804千克，二胎为772千克。两个胎次的平均品系空怀天数和产犊间隔都较短，二胎相差10天。其他繁殖差异较小或不显著。对产量的选择对繁殖适应性有适度影响。
