Vanderick S, Troch T, Gillon A, Glorieux G, Gengler N
Animal Science Unit, Gembloux Agro-Bio Tech, University of Liège, Gembloux, Belgium.
J Anim Breed Genet. 2014 Dec;131(6):513-21. doi: 10.1111/jbg.12105. Epub 2014 Jun 26.
Calving ease scores from Holstein dairy cattle in the Walloon Region of Belgium were analysed using univariate linear and threshold animal models. Variance components and derived genetic parameters were estimated from a data set including 33,155 calving records. Included in the models were season, herd and sex of calf × age of dam classes × group of calvings interaction as fixed effects, herd × year of calving, maternal permanent environment and animal direct and maternal additive genetic as random effects. Models were fitted with the genetic correlation between direct and maternal additive genetic effects either estimated or constrained to zero. Direct heritability for calving ease was approximately 8% with linear models and approximately 12% with threshold models. Maternal heritabilities were approximately 2 and 4%, respectively. Genetic correlation between direct and maternal additive effects was found to be not significantly different from zero. Models were compared in terms of goodness of fit and predictive ability. Criteria of comparison such as mean squared error, correlation between observed and predicted calving ease scores as well as between estimated breeding values were estimated from 85,118 calving records. The results provided few differences between linear and threshold models even though correlations between estimated breeding values from subsets of data for sires with progeny from linear model were 17 and 23% greater for direct and maternal genetic effects, respectively, than from threshold model. For the purpose of genetic evaluation for calving ease in Walloon Holstein dairy cattle, the linear animal model without covariance between direct and maternal additive effects was found to be the best choice.
利用单变量线性和阈性状动物模型分析了比利时瓦隆地区荷斯坦奶牛的产犊难易度评分。从包含33155条产犊记录的数据集中估计方差分量和导出的遗传参数。模型中的固定效应包括季节、牛群、犊牛性别×母牛年龄类别×产犊组交互作用，随机效应包括牛群×产犊年份、母体永久环境以及动物直接加性遗传效应和母体加性遗传效应。模型拟合时，直接加性遗传效应和母体加性遗传效应之间的遗传相关性要么进行估计，要么限定为零。线性模型下产犊难易度的直接遗传力约为8%，阈性状模型下约为12%。母体遗传力分别约为2%和4%。发现直接加性效应和母体加性效应之间的遗传相关性与零无显著差异。根据拟合优度和预测能力对模型进行比较。从85118条产犊记录中估计比较标准，如均方误差、观察到的和预测的产犊难易度评分之间的相关性以及估计育种值之间的相关性。结果表明，线性模型和阈性状模型之间差异不大，尽管线性模型后代公牛数据子集估计育种值之间的相关性，直接遗传效应和母体遗传效应分别比阈性状模型高17%和23%。对于瓦隆荷斯坦奶牛产犊难易度的遗传评估，发现直接加性效应和母体加性效应之间无协方差的线性动物模型是最佳选择。
