Wageningen University & Research, Animal Breeding and Genomics, PO Box 338, 6700 AH Wageningen, the Netherlands.
Wageningen University & Research, Animal Breeding and Genomics, PO Box 338, 6700 AH Wageningen, the Netherlands.
J Dairy Sci. 2021 Feb;104(2):1967-1981. doi: 10.3168/jds.2020-19245. Epub 2020 Dec 11.
Resilience is the ability of cows to cope with disturbances, such as pathogens or heat waves. To breed for improved resilience, it is important to know whether resilience genetically changes throughout life. Therefore, the aim was to perform a genetic analysis on 2 resilience indicators based on data from 3 periods of the first lactation (d 11-110, 111-210, and 211-340) and the first 3 full lactations, and to estimate genetic correlations with health traits. The resilience indicators were the natural log-transformed variance (LnVar) and lag-1 autocorrelation (r) of daily deviations in milk yield from an expected lactation curve. Low LnVar and r indicate low variability in daily milk yield and quick recovery, and were expected to indicate good resilience. Data of 200,084 first, 155,784 second, and 89,990 third lactations were used. Heritabilities were similar based on different lactation periods (0.12-0.15 for LnVar, 0.05-0.06 for r). However, the heritabilities of the resilience indicators based on full first lactation were higher than those based on lactation periods (0.20 for LnVar, 0.08 for r), due to lower residual variances. Heritabilities decreased from 0.20 in full lactation 1 to 0.19 in full lactation 3 for LnVar and from 0.08 to 0.06 for r. For LnVar, as well as for r, the strongest genetic correlation between lactation periods was between period 2 and 3 (0.97 for LnVar, 0.96 for r) and the weakest between period 1 and 3 (0.81 for LnVar, 0.65 for r). Similarly, for both traits the genetic correlation between full lactations was strongest between lactations 2 and 3 (0.99 for LnVar, 0.95 for r) and weakest between lactations 1 and 3 (0.91 for LnVar, 0.71 for r). For LnVar, genetic correlations with resilience-related traits, such as udder health, ketosis, and longevity, adjusted for correlations with milk yield, were almost always favorable (-0.59 to 0.02). In most cases these genetic correlations were stronger based on full lactations than on lactation periods. Genetic correlations were similar across full lactations, but the correlation with udder health increased substantially from -0.31 in lactation 1 to -0.51 in lactation 3. For r, genetic correlations with resilience-related traits were always favorable in lactation period 1 and in most full lactations, but not in the other lactation periods. However, correlations were weak (-0.27 to 0.15). Therefore, as a resilience indicator for breeding, LnVar is preferred over r. A multitrait index based on estimated breeding values for LnVar in lactations 1, 2, and 3 is recommended to improve resilience throughout the lifetime of a cow.
奶牛的弹性是指其应对病原体或热浪等干扰的能力。为了培育具有更高弹性的品种，了解弹性是否会在整个生命周期中发生遗传变化非常重要。因此，本研究的目的是基于第一泌乳期的 3 个时期（d11-110、111-210 和 211-340）和前 3 个完整泌乳期的数据，对 2 个基于弹性的指标进行遗传分析，并估计与健康性状的遗传相关性。这 2 个弹性指标分别为基于预期泌乳曲线的每日产奶量偏差的自然对数变换方差（LnVar）和滞后 1 自相关（r）。低 LnVar 和 r 表明每日产奶量的变异性低且恢复速度快，预计具有良好的弹性。共使用了 200,084 个第一泌乳期、155,784 个第二泌乳期和 89,990 个第三泌乳期的数据。不同泌乳期的遗传力相似（LnVar 为 0.12-0.15，r 为 0.05-0.06）。然而，基于完整第一泌乳期的弹性指标的遗传力高于基于泌乳期的遗传力（LnVar 为 0.20，r 为 0.08），因为残差方差较低。LnVar 的遗传力从完整泌乳期 1 的 0.20 下降到完整泌乳期 3 的 0.19，r 的遗传力从 0.08 下降到 0.06。对于 LnVar 和 r，泌乳期之间最强的遗传相关性是在第 2 期和第 3 期之间（LnVar 为 0.97，r 为 0.96），最弱的是在第 1 期和第 3 期之间（LnVar 为 0.81，r 为 0.65）。同样，对于这两个性状，完整泌乳期之间的遗传相关性在第 2 期和第 3 期之间最强（LnVar 为 0.99，r 为 0.95），在第 1 期和第 3 期之间最弱（LnVar 为 0.91，r 为 0.71）。对于 LnVar，与弹性相关的性状（如乳房健康、酮病和长寿）的遗传相关性在调整与产奶量的相关性后，几乎总是有利的（-0.59 至 0.02）。在大多数情况下，基于完整泌乳期的这些遗传相关性强于基于泌乳期的遗传相关性。遗传相关性在完整泌乳期之间相似，但与乳房健康的相关性从泌乳期 1 的-0.31 大幅增加到泌乳期 3 的-0.51。对于 r，与弹性相关的性状的遗传相关性在泌乳期 1 和大多数完整泌乳期都是有利的，但在其他泌乳期不是。然而，相关性很弱（-0.27 至 0.15）。因此，作为一种用于培育的弹性指标，LnVar 优于 r。建议基于第 1、2 和 3 泌乳期 LnVar 的估计育种值构建多性状指数，以提高奶牛一生的弹性。
