Waldron D F, Thomas D L
Department of Animal Sciences, University of Illinois, Urbana 61801.
J Anim Sci. 1992 Nov;70(11):3333-44. doi: 10.2527/1992.70113333x.
The variance and covariance components needed to estimate heritabilities of and genetic correlations among litter size, ovulation rate, scrotal circumference, and BW in a flock of Rambouillet sheep were estimated using REML via an expectation-maximization type algorithm. The heritability estimates from univariate analyses were .14, .21, .25, .36, and .15 for litter size, ovulation rate, scrotal circumference, 180-d BW of females, and 180-d BW of males, respectively, and average heritability estimates from bivariate analyses were .19, .20, .20, .34, and .10 for litter size, ovulation rate, scrotal circumference, 180-d BW of females, and 180-d BW of males, respectively. The genetic correlation between litter size and ovulation rate was near unity. Body weight in ewes had a moderate genetic correlation with both litter size (.22) and ovulation rate (.20) and a low residual correlation with both litter size (.03) and ovulation rate (.09). The genetic correlation between BW in rams and scrotal circumference was 0, whereas the residual correlation was .71. The genetic correlations of scrotal circumference with litter size and ovulation rate were -.25 and +.20, respectively.
利用一种期望最大化类型的算法，通过限制最大似然法（REML）估计了兰布耶羊群中窝产仔数、排卵率、阴囊周长和体重的遗传力以及这些性状间的遗传相关性所需的方差和协方差分量。单变量分析得出的遗传力估计值分别为：窝产仔数0.14、排卵率0.21、阴囊周长0.25、180日龄母羊体重0.36、180日龄公羊体重0.15；双变量分析得出的平均遗传力估计值分别为：窝产仔数0.19、排卵率0.20、阴囊周长0.20、180日龄母羊体重0.34、180日龄公羊体重0.10。窝产仔数和排卵率之间的遗传相关性接近1。母羊体重与窝产仔数（0.22）和排卵率（0.20）均具有中等遗传相关性，与窝产仔数（0.03）和排卵率（0.09）的残差相关性均较低。公羊体重与阴囊周长之间的遗传相关性为0，而残差相关性为0.71。阴囊周长与窝产仔数和排卵率的遗传相关性分别为-0.25和+0.20。
