Hagger C
Institute of Animal Sciences, Swiss Federal Institute of Technology, ETH-Zentrum TAN, Zurich.
J Anim Sci. 1998 Feb;76(2):452-7. doi: 10.2527/1998.762452x.
Twelve models were fitted to early growth data of two Swiss sheep breeds to investigate their suitability for evaluation of breeding values. Models were identical for fixed parity, litter size, sex and lambing season effects, random flock-year, and direct genetic effects but differed for combinations of random litter, permanent environmental, ram-flock, and maternal genetic effects. Records of average daily gain to 30 d of 25,564 lambs of the Black-Brown Mountain Sheep (SBS) and of 26,391 lambs of the White Alpine Sheep (WAS) born 1989 to 1995 and their pedigrees were available. A single-trait animal model was fitted by the restricted maximum likelihood method. The information criterion of a particular model (i.e., the maximum of the likelihood function adjusted for the number of independently estimated parameters) was used to evaluate the models for their fitting power. The litter effect accounted for between 26 and 31% of the phenotypic variance, with little variation within breed. Models containing the ram-flock effect provided a better fit of the data than otherwise identical models. This effect contributed 6 and 4% to the phenotypic variance in the two breeds and strongly influenced estimates of other components. The proportion of phenotypic variance due to the flock-year effect was 23 and 25% without and 19 and 23% including the ram-flock effect in the model in the two breeds. Including permanent environmental effect of the ewe in addition to litter effect led to a better fit of the data. Depending on the model, it then contributed between 3 and 6% to the phenotypic variance. Fitting the ram-flock effect reduced heritability considerably and increased the breed difference of the estimates of this parameter. Estimates ranging from .16 to .10 and from .08 to .14 were obtained for the SBS and WAS breeds, respectively. For models without the ram-flock effect, negative estimates of the direct-maternal correlation of between -.38 and -.45 were observed. Including the ram-flock effect reduced this correlation substantially to between -.08 and -.17. Including the direct-maternal covariance in addition to the ram-flock effect did not improve the fit any further in either breed. Ranking of the models investigated differed between breeds, but the same model provided the best fit. It contained the random litter, permanent environmental, ram-flock, direct, and maternal genetic effects, but not the covariance between the last two.
对两个瑞士绵羊品种的早期生长数据拟合了12种模型，以研究它们对育种值评估的适用性。固定胎次、产仔数、性别和产羔季节效应、随机群体-年份效应以及直接遗传效应的模型相同，但随机窝仔效应、永久环境效应、公羊-群体效应和母系遗传效应的组合不同。有1989年至1995年出生的25564只黑棕色山地绵羊（SBS）羔羊和26391只白色高山绵羊（WAS）羔羊30日龄平均日增重记录及其系谱。采用约束最大似然法拟合单性状动物模型。用特定模型的信息准则（即根据独立估计参数数量调整后的似然函数最大值）来评估模型的拟合能力。窝仔效应占表型方差的26%至31%，品种内差异不大。包含公羊-群体效应的模型比其他相同模型对数据的拟合更好。该效应在两个品种的表型方差中分别占6%和4%，并强烈影响其他成分的估计值。在两个品种中，不包含公羊-群体效应时群体-年份效应占表型方差的比例分别为23%和25%，包含公羊-群体效应时分别为19%和23%。除窝仔效应外，纳入母羊的永久环境效应能使数据拟合得更好。根据模型不同，其占表型方差的比例在3%至6%之间。拟合公羊-群体效应会显著降低遗传力，并增加该参数估计值的品种差异。SBS和WAS品种的遗传力估计值分别在0.16至0.10和0.08至0.14之间。对于不包含公羊-群体效应的模型，直接-母系相关性的估计值在-0.38至-0.45之间为负。包含公羊-群体效应会使该相关性大幅降低至-0.08至-0.17之间。除公羊-群体效应外再纳入直接-母系协方差，在两个品种中均未进一步改善拟合效果。所研究模型的排名因品种而异，但同一模型拟合效果最佳。它包含随机窝仔效应、永久环境效应、公羊-群体效应、直接和母系遗传效应，但不包含后两者之间的协方差。
