Van Doormaal B J, Schaeffer L R, Kennedy B W
J Dairy Sci. 1985 Jul;68(7):1763-9. doi: 10.3168/jds.S0022-0302(85)81025-0.
Hazard functions were plotted and troughs were used to define stayability traits that best coincided with the time of culling decisions. Traits evaluated were stayability to 17, 30, 43, and 55 mo of productive life and stayability to 42, 54, 66, and 78 mo of total life. Holstein data from Record of Performance and supervised Dairy Herd Improvement and Dairy Herd Analysis Service testing programs formed two data sets with 243,348 and 118,362 daughters of 10,723 and 4,583 sires, respectively, and were used to estimate stayability heritabilities and correlations. Variance components were estimated by Henderson's new method using a model that included a fixed herd-year-season of first calving effect and random sire and error effects. Heritabilities for stayability to 17, 30, 43, and 55 mo of productive life were .025, .040, .039, and .033, respectively, for the Record of Performance data and .010, .017, .023, and .033, respectively, for the Dairy Herd Improvement-Dairy Herd Analysis Service supervised data. Heritability estimates for stayability to 42, 54, 66, and 78 mo of total life were .051, .040, .045, and .059, respectively, for the Dairy Herd Improvement-Dairy Herd Analysis Service supervised data. Genetic correlations among productive life traits were usually very high and approached unity. Genetic correlations among total life traits were lower and more variable. Most phenotypic correlations were moderately high but some were low. Stayability to 17 mo of productive life was concluded to be the best trait for incorporation into a selection program if evaluation of sires for longevity is desired.
绘制了风险函数，并利用波谷来定义与淘汰决策时间最相符的可留种性状。所评估的性状包括产奶期17、30、43和55月龄时的可留种能力以及整个生命周期42、54、66和78月龄时的可留种能力。来自生产性能记录以及受监督的奶牛群改良和奶牛群分析服务测试项目的荷斯坦数据分别形成了两个数据集，其中一个数据集包含10723头公牛的243348头女儿，另一个数据集包含4583头公牛的118362头女儿，并用于估计可留种能力的遗传力和相关性。方差成分采用亨德森新方法，通过包含首次产犊固定畜群-年份-季节效应以及随机公牛和误差效应的模型进行估计。对于生产性能记录数据，产奶期17、30、43和55月龄时可留种能力的遗传力分别为0.025、0.040、0.039和0.033；对于奶牛群改良-奶牛群分析服务受监督数据，相应的遗传力分别为0.010、0.017、0.023和0.033。对于奶牛群改良-奶牛群分析服务受监督数据，整个生命周期42、54、66和78月龄时可留种能力的遗传力估计值分别为0.051、0.040、0.045和0.059。产奶期性状之间的遗传相关性通常非常高，接近1。整个生命周期性状之间的遗传相关性较低且变化更大。大多数表型相关性中等偏高，但也有一些较低。如果希望评估公牛的长寿性，产奶期17月龄时的可留种能力被认为是纳入选择计划的最佳性状。
