Bennett G L, Gregory K E
U.S. Department of Agriculture, ARS, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, NE 68933-0166, USA.
J Anim Sci. 1996 Nov;74(11):2598-611. doi: 10.2527/1996.74112598x.
Genetic and environmental (co)variances for birth weight, adjusted 200-d weight, and postweaning gain were estimated in nine parental and three composite populations of beef cattle. The parental breeds were Angus (A), Braunvieh (B), Charolais (C), Gelbvieh (G), Hereford (H), Limousin (L), Pinzgauer (P), Red Poll (R), and Simmental (S). The composites were MARC I (1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A), MARC II (1/4 G, 1/4 S, 1/4 H, 1/4 A), and MARC III (1/4 R, 1/4 P, 1/4 H, 1/4 A). Heritabilities of additive direct genetic effects for birth weight (.50) and postweaning gain (.49) were greater than for 200-d weight (.32). Heritabilities of additive maternal effects of .09 for birth weight and .10 for 200-d weight were much smaller than direct effect heritabilities. Heritabilities were larger in composites than in parental breeds for additive direct effects of all three traits but smaller for maternal 200-d weight. Correlations were high and positive for direct genetic effects of the three weight traits and higher in composites than in the parental breeds. Correlations between direct and maternal genetic effects for both birth weight and 200-d weight were near zero. Some differences in variances among populations were correlated with differences in weight and milk yield. Heavier populations had larger variances, supporting the use of logarithmic transformation of weights to stabilize variances among genetic groups. Increased average milk yield was correlated with decreased phenotypic variance of 200-d weight. Average milk yield was also implicated in the expression of direct and maternal genetic effects for 200-d weight and their covariance. Comparison of univariate and multivariate estimates of genetic variances suggested that it is important to include birth weight in multivariate analyses of all weight traits to account for increased preweaning mortality of calves with extremely heavy or light birth weights. Based on heritability estimates, within-herd selection in composites should be at least as effective as in purebreds. Some differences among populations in genetic parameters were indicated, especially maternal 200-d weight and its correlations with other traits.
在九个肉牛亲本群体和三个合成群体中，对出生体重、200日龄体重校正值以及断奶后增重的遗传和环境（协）方差进行了估计。亲本品种包括安格斯牛（A）、西门塔尔牛（B）、夏洛来牛（C）、利木赞牛（G）、海福特牛（H）、利木赞牛（L）、平茨高尔牛（P）、红白花牛（R）和西门塔尔牛（S）。合成群体包括MARC I（1/4 B、1/4 C、1/4 L、1/8 H、1/8 A）、MARC II（1/4 G、1/4 S、1/4 H、1/4 A）和MARC III（1/4 R、1/4 P、1/4 H、1/4 A）。出生体重（0.50）和断奶后增重（0.49）的加性直接遗传效应的遗传力大于200日龄体重（0.32）的遗传力。出生体重的加性母体效应遗传力为0.09，200日龄体重的为0.10，远小于直接效应遗传力。对于所有三个性状的加性直接效应，合成群体中的遗传力大于亲本品种，但200日龄体重的母体效应遗传力则较小。三个体重性状的直接遗传效应之间的相关性较高且为正，合成群体中的相关性高于亲本品种。出生体重和200日龄体重的直接和母体遗传效应之间的相关性接近零。群体间的一些方差差异与体重和产奶量差异相关。较重的群体方差较大，这支持对体重进行对数变换以稳定遗传群体间的方差。平均产奶量增加与200日龄体重的表型方差降低相关。平均产奶量还与200日龄体重的直接和母体遗传效应及其协方差的表达有关。单变量和多变量遗传方差估计值的比较表明，在所有体重性状的多变量分析中纳入出生体重很重要，以考虑出生体重极重或极轻的犊牛断奶前死亡率增加的情况。基于遗传力估计，合成群体内的群体选择至少应与纯种群体一样有效。表明群体间在遗传参数上存在一些差异，特别是母体200日龄体重及其与其他性状的相关性。
