Estimation of the genetic milk yield parameters of Holstein cattle under heat stress in South Korea.
Estimation of the genetic milk yield parameters of Holstein cattle under heat stress in South Korea.
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DOI：
10.5713/ajas.18.0258
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发表时间：
2019-03
期刊：
影响因子：
--
通讯作者：
Cho K
中科院分区：
文献类型：
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作者：
Lee S;Do C;Choy Y;Dang C;Mahboob A;Cho K
本研究的目的是调查每日产奶量的遗传成分，并使用温度-湿度指数 (THI) 根据热应激下的估计育种值 (EBV) 对韩国公牛进行重新排名。这项研究使用了 2000 年 1 月至 2017 年 2 月期间收集的 125,312 条每月测试日记录，涉及韩国 647 个农场的 19,889 头荷斯坦奶牛。牛奶产量数据是从奶牛遗传改良中心和韩国动物改良协会这两个机构收集的，气象数据是使用安装在韩国各地的自动地面观测系统 (ASOS) 从 41 个区域气象站获得的。使用 THI 的随机回归模型根据测试日记录来估计耐热性的遗传参数。该模型包括牛群年份季节、产犊年龄和产奶天数作为固定效应，以及耐热性作为加性遗传效应、永久性环境效应以及直接加性和永久性环境效应。低于 THI 阈值（≤72；无热应激），耐热性方差为零。然而，随着 THI 超过阈值，耐热性方差开始增加。遗传加性效应与耐热效应之间的协方差为-0.33。产奶量的遗传力估计范围为 0.111 至 0.176（平均值：0.128）。遗传力随着 THI 的增加而略有下降，并在 THI 为 79 时开始增加。预测的公牛 EBV 排名随 THI 变化。我们得出的结论是，使用 THI 函数进行遗传评估可能有助于在韩国选择耐热性公牛。
The objective of this study was to investigate the genetic components of daily milk yield and to re-rank bulls in South Korea by estimated breeding value (EBV) under heat stress using the temperature-humidity index (THI). This study was conducted using 125,312 monthly test-day records, collected from January 2000 to February 2017 for 19,889 Holstein cows from 647 farms in South Korea. Milk production data were collected from two agencies, the Dairy Cattle Genetic Improvement Center and the Korea Animal Improvement Association, and meteorological data were obtained from 41 regional weather stations using the Automated Surface Observing System (ASOS) installed throughout South Korea. A random regression model using the THI was applied to estimate genetic parameters of heat tolerance based on the test-day records. The model included herd-year-season, calving age, and days-in-milk as fixed effects, as well as heat tolerance as an additive genetic effect, permanent environmental effect, and direct additive and permanent environmental effect. Below the THI threshold (≤72; no heat stress), the variance in heat tolerance was zero. However, the heat tolerance variance began to increase as THI exceeded the threshold. The covariance between the genetic additive effect and the heat tolerance effect was −0.33. Heritability estimates of milk yield ranged from 0.111 to 0.176 (average: 0.128). Heritability decreased slightly as THI increased, and began to increase at a THI of 79. The predicted bull EBV ranking varied with THI. We conclude that genetic evaluation using the THI function could be useful for selecting bulls for heat tolerance in South Korea.