Department of Animal Bioscience, Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland P61 C996; Department of Biological Sciences, Munster Technological University, Bishopstown Campus, Co. Cork, Ireland T12 P928.
Department of Biological Sciences, Munster Technological University, Bishopstown Campus, Co. Cork, Ireland T12 P928.
J Dairy Sci. 2022 Sep;105(9):7550-7563. doi: 10.3168/jds.2022-22026. Epub 2022 Jul 22.
The cumulative improvement achieved in the genetic merit for reproductive performance in dairy populations will likely improve dairy cow longevity; therefore, it is time to reassess whether linear type traits are still suitable predictors of survival in an aging dairy cow population. The objective of the present study was therefore to estimate the genetic correlations between linear type traits and survival from one parity to the next and, in doing so, evaluate if those genetic correlations change with advancing parity. After edits, 152,894 lactation survival records (first to ninth parity) were available from 52,447 Holstein-Friesian cows, along with linear type trait records from 52,121 Holstein-Friesian cows. A series of bivariate random regression models were used to estimate the genetic covariances between survival in different parities and each linear type trait. Heritability estimates for survival per parity ranged from 0.02 (SE = 0.004; first parity) to 0.05 (SE = 0.01; ninth parity). Pairwise genetic correlations between survival among different parities varied from 0.42 (first and ninth parity) to 1.00 (eighth to ninth parity), with the strength of these genetic correlations being inversely related to the interval between the compared parities. The genetic correlations between survival and the individual linear type traits varied across parities for 9 of the 20 linear type traits examined, but the correlations with only 3 of these linear type traits strengthened as the cows aged; these 3 traits were rear udder height, teat length, and udder depth. Given that linear type traits are frequently scored in first parity and are genetically correlated with survival in older parities, they may be suitable early predictors of survival, especially for later parity cows. Additionally, the direction of the genetic correlations between survival and rear udder height, teat length, and udder depth did not change between parities; hence, selection for survival in older parities using these linear type traits should not hinder genetic improvement for survival in younger parities.
奶牛群体繁殖性能遗传改良的累积进展可能会提高奶牛的寿命；因此，现在是时候重新评估线性体型特征是否仍然是老龄化奶牛群体生存的合适预测指标了。本研究的目的是估计线性体型特征与下一胎次之间的生存的遗传相关性，并在此过程中评估这些遗传相关性是否随胎次的增加而变化。经过编辑，从 52447 头荷斯坦-弗里森奶牛中获得了 152894 个泌乳生存记录（第一至第九胎次），以及 52121 头荷斯坦-弗里森奶牛的线性体型特征记录。使用一系列双变量随机回归模型来估计不同胎次之间生存和每个线性体型特征之间的遗传协方差。每胎次的生存遗传力估计值范围从 0.02（SE=0.004；第一胎次）到 0.05（SE=0.01；第九胎次）。不同胎次之间生存的成对遗传相关性从 0.42（第一和第九胎次）到 1.00（第八和第九胎次）不等，这些遗传相关性的强度与比较胎次之间的间隔呈反比。在 20 个线性体型特征中，有 9 个特征的生存与个体线性体型特征之间的遗传相关性在不同胎次之间存在差异，但只有其中 3 个线性体型特征的相关性随着奶牛年龄的增长而增强；这 3 个特征是后乳房高度、乳头长度和乳房深度。鉴于线性体型特征通常在第一胎次进行评分，并且与较老胎次的生存存在遗传相关性，因此它们可能是生存的早期预测指标，尤其是对于较晚胎次的奶牛。此外，生存与后乳房高度、乳头长度和乳房深度之间的遗传相关性的方向在胎次之间没有变化；因此，使用这些线性体型特征对较老胎次的生存进行选择不应阻碍对较年轻胎次的生存的遗传改良。
