Department of Agricultural Sciences, University of Sassari, 07100 Sassari, Italy; Department of Animal and Dairy Science, University of Georgia, Athens 30602.
Department of Agricultural, Forestry and Alimentary Sciences, University of Torino, 10095 Grugliasco, Italy.
J Dairy Sci. 2020 Jun;103(6):5227-5233. doi: 10.3168/jds.2019-17421. Epub 2020 Apr 8.
Functional traits, such as fertility and lactation persistency, are becoming relevant breeding goals for dairy cattle. Fertility is a key element for herd profitability and animal welfare; in particular, calving interval (CIN) is an indicator of female fertility that can be easily recorded. Lactation persistency (LPE; i.e., the ability of a cow to maintain a high milk yield after the lactation peak) is economically important and is related to several other traits, such as feed efficiency, health, and reproduction. The selection of these functional traits is constrained by their low heritability. In this study, variance components for CIN and LPE in the Italian Simmental cattle breed were estimated using genomic and pedigree information under the single-step genomic framework. A data set of 594,257 CIN records (from 275,399 cows) and 285,213 LPE records (from 1563,389 cows) was considered. Phenotypes were limited up to the third parity. The pedigree contained about 2 million animals, and 7,246 genotypes were available. Lactation persistency was estimated using principal component analysis on test day records, with higher values of the second extracted principal component (PC2) values associated with lower LPE, and lower PC2 values associated with higher LPE. Heritability of CIN and LPE were estimated using single-trait repeatability models. A multiple-trait analysis using CIN and production traits (milk, fat, and protein yields) was performed to estimate genetic correlations among these traits. Heritability for CIN in the single-trait model was low (0.06 ± 0.002). Unfavorable genetic correlations were found between CIN and production traits. A measure of LPE was derived using principal component analysis on test day records. The heritability and repeatability of LPE were 0.11 ± 0.004 and 0.20 ± 0.02, respectively. Genetic correlation between CIN and LPE was weak but had a favorable direction. Despite the low heritability estimates, results of the present work suggest the possibility of including these traits in the Italian Simmental breeding program. The use of a single-step approach may provide better results for young genotyped animals without their own phenotypes.
功能性状，如繁殖力和泌乳持久力，正在成为奶牛养殖的重要选育目标。繁殖力是牛群盈利能力和动物福利的关键因素；特别是产犊间隔（CIN）是衡量母牛繁殖力的一个指标，很容易记录。泌乳持久力（LPE；即母牛在泌乳高峰期后维持高产奶量的能力）在经济上很重要，与其他几个性状有关，如饲料效率、健康和繁殖力。这些功能性状的选择受到其低遗传力的限制。在这项研究中，使用单步基因组框架下的基因组和系谱信息，估计了意大利西门塔尔牛品种的 CIN 和 LPE 的方差分量。考虑了一个包含 594257 个 CIN 记录（来自 275399 头母牛）和 285213 个 LPE 记录（来自 1563389 头母牛）的数据集。表型限制在第三胎次以内。系谱中大约有 200 万头动物，有 7246 个基因型。利用主成分分析在测试日记录中估计了泌乳持久力，与较低 LPE 相关的第二提取主成分（PC2）值较高，与较高 LPE 相关的 PC2 值较低。使用单性状重复力模型估计了 CIN 和 LPE 的遗传力。使用 CIN 和生产性状（牛奶、脂肪和蛋白质产量）的多性状分析，估计了这些性状之间的遗传相关性。单性状模型中 CIN 的遗传力较低（0.06±0.002）。CIN 与生产性状之间存在不利的遗传相关性。使用测试日记录上的主成分分析得出了 LPE 的度量标准。LPE 的遗传力和重复力分别为 0.11±0.004 和 0.20±0.02。CIN 和 LPE 之间的遗传相关性较弱，但方向有利。尽管遗传力估计值较低，但本研究结果表明，这些性状有可能被纳入意大利西门塔尔牛的选育计划。单步方法的使用可能会为没有自己表型的年轻基因型动物提供更好的结果。
