Guinan Fiona L, Fourdraine Robert H, Peñagaricano Francisco, Weigel Kent A
Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI 53706.
Dairy Records Management Systems, Raleigh, NC 27603.
JDS Commun. 2025 Mar 1;6(2):237-240. doi: 10.3168/jdsc.2024-0635. eCollection 2025 Mar.
The availability of daily milk weights and pen location information provides an interesting opportunity to capture additional data and review how contemporary groups are defined for dairy cattle genetic evaluations. In the United States, dairy cows in larger herds are grouped into pens according to various characteristics such as parity, production level, reproductive status, lactation stage, and health status. Our dataset included pen location information for each daily milk weight, so instead of using herd-year-season of calving to form contemporary groups, we used herd-pen-milking date to more precisely model the environmental effects cows experience at the pen level on a given day. Our dataset included 21,000,951 aggregated daily milk records from 114,243 first-parity Holstein cows milked 3 times daily in conventional parlor systems in 157 herds representing 29 US states. Our phenotype of interest was daily milk weight, and alternative repeatability animal models were used to estimate genetic parameters and predict breeding values. Age at first calving (6 levels) and DIM (10 levels) were included as fixed effects and cow (114,243 levels) was included as a random effect. Contemporary group effects included a fixed or random herd-year-season of calving effect (1,492 levels) and a fixed or random herd-pen-milking date effect (285,592 levels). Genetic parameters (kg; posterior SD) were estimated using GIBBSF90+ software. The additive genetic variance ranged from 10.48 (0.60) to 24.12 (0.66), herd-year-season variance was 10.34 (0.40), herd-pen-milking date variance ranged from 4.91 (0.02) to 4.96 (0.02), permanent environmental variance ranged from 10.65 (0.44) to 16.94 (0.30), and residual variance ranged from 11.81 (0.01) to 14.60 (0.01). Heritability estimates ranged from 0.21 (0.01) to 0.47 (0.01), and repeatability estimates ranged from 0.51 (0.01) to 0.71 (0.01), and mean reliability of sires' breeding value predictions ranged from 0.81 to 0.89. Although caution is needed when disentangling associations between genetic effects, permanent environmental effects, and herd-pen-milking date contemporary groups, our results suggest that using daily milk weights and pen locations may improve the precision of genetic evaluations through increased sire PTA reliabilities for milk production traits in dairy cattle.
每日产奶量数据以及牛栏位置信息的可得性提供了一个有趣的机会，可用于获取更多数据，并审视在奶牛遗传评估中当代组是如何定义的。在美国，大型牛群中的奶牛会根据胎次、生产水平、繁殖状态、泌乳阶段和健康状况等各种特征被分组到不同牛栏。我们的数据集包含了每条每日产奶量记录的牛栏位置信息，因此，我们没有使用产犊的畜群 - 年份 - 季节来形成当代组，而是使用畜群 - 牛栏 - 挤奶日期，以便更精确地模拟奶牛在给定日期在牛栏层面所经历的环境影响。我们的数据集包含来自114,243头头胎荷斯坦奶牛的21,000,951条汇总的每日产奶记录，这些奶牛在代表美国29个州的157个牛群中采用传统挤奶厅系统，每天挤奶3次。我们感兴趣的表型是每日产奶量，并且使用了替代重复性动物模型来估计遗传参数并预测育种值。首次产犊年龄（6个水平）和泌乳天数（10个水平）被作为固定效应纳入，奶牛（114,243个水平）被作为随机效应纳入。当代组效应包括固定或随机的产犊畜群 - 年份 - 季节效应（1,492个水平）以及固定或随机的畜群 - 牛栏 - 挤奶日期效应（285,592个水平）。遗传参数（千克；后验标准差）使用GIBBSF90 +软件进行估计。加性遗传方差范围为10.48（0.60）至24.12（0.66），畜群 - 年份 - 季节方差为10.34（0.40），畜群 - 牛栏 - 挤奶日期方差范围为4.91（0.02）至4.96（0.02），永久环境方差范围为10.65（0.44）至16.94（0.30），残差方差范围为11.81（0.01）至14.60（0.01）。遗传力估计值范围为0.21（0.01）至0.47（0.01），重复性估计值范围为0.51（0.01）至0.71（0.01），种公牛育种值预测的平均可靠性范围为0.81至0.89。尽管在解析遗传效应、永久环境效应和畜群 - 牛栏 - 挤奶日期当代组之间的关联时需要谨慎，但我们的结果表明，使用每日产奶量和牛栏位置可能会通过提高奶牛产奶性状的种公牛预测传递能力（PTA）可靠性来提高遗传评估的精度。
