Genetic components of heat stress for dairy cattle with multiple lactations
Genetic components of heat stress for dairy cattle with multiple lactations
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DOI：
10.3168/jds.2008-1928
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发表时间：
2009-11-01
影响因子：
3.5
通讯作者：
Tsuruta, S.
中科院分区：
文献类型：
--
作者：
Aguilar, I.;Misztal, I.;Tsuruta, S.
数据包括格鲁吉亚38，608头荷斯坦奶牛的第一、第二和第三胎产奶量、脂肪和蛋白质产量的585，119个试验日记录。每日温度-湿度指数（THI）可从公共气象站获得。模型包括一个重复性测试日模型与THI的函数和测试日随机回归模型使用线性样条结在5，50，200和305天的牛奶和THI的函数的随机回归。在重复性模型中，随机效应是加性遗传和永久环境，在随机回归模型中，随机效应是加性遗传、永久环境和畜群年。此外，模型包括牛群试验日、产犊年龄、挤奶频率和泌乳阶段的固定效应。重复力模型下，所有产量性状的表型方差从第一胎到第二胎增加了50%~ 60%，从第二胎到第三胎增加了12%~ 15%。一般加性遗传方差增加了25%至35%，从第一至第二胎的所有产量性状，但略有下降，从第二至第三胎的牛奶和蛋白质产量。耐热性的遗传方差从第一胎到第二胎增加了一倍，从第二胎到第三胎增加了20%到100%。一般加性效应间的遗传相关在第一胎和第二胎之间最低（0.84 ~ 0.88），在第二胎和第三胎之间最高（0.96 ~ 0.98）。产次间耐热性效应的遗传相关为0.56 ~ 0.79。一般效应和耐热效应与产量性状的遗传相关在-0.30 ~-0.50之间。在随机回归模型中，产奶量耐热性的遗传方差约为重复性模型的一半。对于产奶量，一般和耐热性效应之间的最负遗传相关（约-0.45）为50至200天之间的第一胎和200至305天之间的第二和第三胎的牛奶。耐热性的遗传方差从第一胎到第三胎大幅度增加。耐热性的遗传估计可能会夸大与重复性模型，因为泌乳的时间，以避免高峰产量在炎热的季节。
Data included 585,119 test-day records for milk, fat, and protein yields from the first, second, and third parities of 38,608 Holsteins in Georgia. Daily temperature-humidity indexes (THI) were available from public weather stations. Models included a repeatability test-day model with a random regression on a function of THI and a test-day random regression model using linear splines with knots at 5, 50, 200, and 305 d in milk and a function of THI. Random effects were additive genetic and permanent environmental in the repeatability model and additive genetic, permanent environmental, and herd year in the random regression model. Additionally, models included fixed effects for herd test day, calving age, milking frequency, and lactation stage. Phenotypic variance increased by 50 to 60% from the first to second parity for all yield traits with the repeatability model and by 12 to 15% from the second to third parity. General additive genetic variance increased by 25 to 35% from the first to second parity for all yield traits but decreased slightly from the second to third parity for milk and protein yields. Genetic variance for heat tolerance doubled from the first to second parity and increased by 20 to 100% from the second to third parity. Genetic correlations among general additive effects were lowest between the first and second parities (0.84 to 0.88) and were highest between the second and third parities (0.96 to 0.98). Genetic correlations among parities for the effect of heat tolerance ranged from 0.56 to 0.79. Genetic correlations between general and heat-tolerance effects across parities and yield traits ranged from -0.30 to -0.50. With the random regression model, genetic variance for heat tolerance for milk yield was approximately one-half that of the repeatability model. For milk yield, the most negative genetic correlation (approximately -0.45) between general and heat-tolerance effects was between 50 and 200 d in milk for the first parity and between 200 and 305 d in milk for the second and third parities. The genetic variance of heat tolerance increased substantially from the first to third parity. Genetic estimates of heat tolerance may be inflated with the repeatability model because of timing of lactations to avoid peak yield during hot seasons.