Estimation of heritability and genetic correlations between milk yield and linear type traits in primiparous Holstein-Friesian cows

ABSTRACT Estimation of genetic variability and genetic correlations between production traits (milk yield, fat yield, fat content, protein yield, and protein content) and selected type traits (angularity, fore udder height, rear udder height, front teat placement, teat length, and udder depth) was done using data sets of 10,860 first-calving Holstein-Friesian cows raised in the territory of the Republic of Serbia. Genetic variance and covariance were obtained using the Restricted Maximum Likelihood (REML) method, VCE v6 software, and the multi-trait mixed model. To enable more precise estimates of values for genetic variances and covariance, a relationship matrix was formed for the individual model (animal model), encompassing 21363 animals. The highest heritability values were obtained for milk yield (0.182), fat yield (0.134), and protein yield (0.170). The lowest heritability estimates were for teat length, front teat placement, rear udder height, and udder depth, all being under 0.110. Genetic correlations between production traits and linear type traits were between −0.131 (fat content and front teat length) and 0.307 (protein yield and fore udder attachment). The largest number of traits shows a positive genetic correlation with the traits of milk yield, which thus indicates possibility of genetic improvements of milk yield in cattle without jeopardizing the type traits or vice versa.

摘要：本研究以塞尔维亚共和国境内饲养的10860头头胎荷斯坦-弗里生奶牛（Holstein-Friesian）的数据集为研究基础，对生产性状（产奶量、乳脂产量、乳脂率、乳蛋白产量、乳蛋白率）与选定的体型性状（体型棱角性、前乳房高度、后乳房高度、前乳头位置、乳头长度、乳房深度）之间的遗传变异与遗传相关进行了估算。研究采用约束最大似然法（Restricted Maximum Likelihood, REML）、VCE v6软件以及多性状混合模型，计算得到遗传方差与协方差。为实现遗传方差与协方差的精准估算，针对个体模型（动物模型，animal model）构建了包含21363个个体的亲缘关系矩阵。产奶量（0.182）、乳脂产量（0.134）与乳蛋白产量（0.170）的遗传力估值最高；乳头长度、前乳头位置、后乳房高度及乳房深度的遗传力估值最低，均低于0.110。生产性状与线性体型性状间的遗传相关系数介于-0.131（乳脂含量与前乳头长度）至0.307（乳蛋白产量与前乳房附着）之间。多数性状与产奶量呈正向遗传相关，这表明可在不损害体型性状的前提下实现奶牛产奶量的遗传改良，反之亦然。