School of Veterinary Science, The University of Queensland, Queensland, Australia.
J Dairy Sci. 2010 Mar;93(3):901-10. doi: 10.3168/jds.2009-2045.
In year-round calving herds, reproductive performance has traditionally been described in relation to each cow's calving date. This research described reproductive performance in year-round and seasonal calving dairy herds using herd-level measures based on interval from each cow's initiation of breeding program date, and assessed interrelationships between such measures. A large, prospective, single cohort study, implemented in 1997 and 1998, included 29,327 cows from 167 Australian dairy herds. Herd reproductive performance was described using 2 measures of primary importance to herd managers: the proportion of cows that became pregnant by 6wk after their initiation of breeding program date (6-wk pregnancy rate) and the proportion of cows that were nonpregnant 21wk after their initiation of breeding program date (21-wk nonpregnancy rate). Measures that contribute to these primary measures (secondary measures) were calculated for each herd for both the first and second 3-wk periods of each cow's breeding program; submission rates were calculated as proportions of cows that were inseminated at least once in the 3-wk period, and conception rates were calculated as the proportions of inseminations in the 3-wk period that resulted in pregnancy. The individual herd was the unit of analysis. The study results indicate that high submission rates are essential if herd reproductive performance is to be achieved. Six-week pregnancy rate was predicted to increase by 6 to 8 percentage points following a 10-percentage-point increase in submission rates in both 3-wk periods, and by 6 to 10 percentage points following a 10-percentage-point increase in conception rates. Submission rates were more variable than conception rates, indicating that managers may be able to achieve large increases in submission rates more easily than substantial increases in conception rates. However, the predicted benefits of increasing submission rates were greatest when conception rates were high and vice versa, highlighting the need to improve both submission and conception rates when both are low. The study results indicate that some herd managers can concurrently achieve high submission and conception rates.
在全年产犊的牛群中，生殖性能传统上是根据每头母牛的产犊日期来描述的。本研究使用基于每头母牛开始配种计划日期的间隔的 herd-level 措施来描述全年和季节性产犊奶牛群的生殖性能，并评估了这些措施之间的相互关系。一项大型的、前瞻性的、单队列研究于 1997 年和 1998 年实施，包括来自澳大利亚 167 个奶牛场的 29327 头奶牛。牛群生殖性能使用对牧场经理非常重要的两个措施来描述：在开始配种计划日期后 6 周内怀孕的母牛比例（6 周怀孕率）和开始配种计划日期后 21 周内未怀孕的母牛比例（21 周未怀孕率）。为每个牛群计算了这两个主要措施的贡献措施（次要措施），这些措施是在每头母牛配种计划的前两个 3 周期间计算的；配种提交率计算为在该 3 周期间至少配种一次的母牛比例，受孕率计算为该 3 周期间导致怀孕的配种比例。分析单位是单个牧场。研究结果表明，如果要实现牛群的生殖性能，高提交率是必不可少的。在两个 3 周期间，配种提交率每增加 10%，6 周怀孕率预计会增加 6 到 8 个百分点，而配种受孕率每增加 10%，6 周怀孕率预计会增加 6 到 10 个百分点。提交率比受孕率更具波动性，这表明经理们可能更容易实现提交率的大幅增加，而不是受孕率的大幅增加。然而，当受孕率较高时，提高提交率的预期收益最大，反之亦然，这突出表明当两者都较低时，需要提高提交率和受孕率。研究结果表明，一些牧场经理可以同时实现高的提交率和受孕率。
