Dodenhoff J, Van Vleck L D, Kachman S D, Koch R M
Department of Animal Science, University of Nebraska, Lincoln 68583, USA.
J Anim Sci. 1998 Oct;76(10):2521-7. doi: 10.2527/1998.76102521x.
Birth and weaning weights adjusted for age of dam from four lines of Hereford cattle were analyzed to determine the relationships among grandmaternal, maternal, and direct genetic effects. Three lines were selected for 1) weaning weight (WWL), 2) yearling weight (YWL), and 3) an index of yearling weight and muscle score (IXL). The fourth line was an unselected control line (CTL). Numbers of observations ranged from 1,699 (CTL) to 2,811 (WWL), and number of animals in the pedigree file ranged from 2,266 to 3,192. Two animal models were used to obtain estimates by REML using an average information method. Model 1 included random direct and maternal genetic, permanent maternal environmental, and residual environmental effects, and fixed sex x year effects. Model 2 additionally included random grandmaternal genetic and permanent grandmaternal environmental effects. For birth weight, Models 1 and 2 gave almost identical estimates for direct and maternal heritability, and for the fraction of variance that was due to maternal permanent environmental effects. Estimates for grandmaternal heritability could be obtained only for IXL (.03) and CTL (.01). For weaning weight, estimates for direct heritability were similar from both models. Estimates for maternal heritability from Model 1 were .18, .20, .13, and .20, and corresponding estimates from Model 2 were .34, .31, .13, and .34 for WWL, YWL, IXL, and CTL, respectively. For IXL, estimates for variances that were due to grandmaternal genetic and grandmaternal permanent environmental variances could not be obtained and were set to zero. Grandmaternal heritability estimates for WWL, YWL, and CTL were .05, .09, and .12. Estimates of correlations between direct and maternal genetic effects were -.13, -.44, -.11, and -.26 for WWL, YWL, IXL, and CTL. Estimates of correlations between direct and grandmaternal genetic effects were .21, .83, and .55, and those between maternal and grandmaternal genetic effects were -.99, -.84, and -.76 for WWL, YWL, and CTL, respectively. These results indicate that grandmaternal effects may be important for weaning weight and that maternal heritability may be underestimated if grandmaternal effects are not included in the model.
对来自四个赫里福德牛品系的、根据母牛年龄调整后的出生体重和断奶体重进行了分析，以确定祖母遗传效应、母体遗传效应和直接遗传效应之间的关系。选择了三个品系用于：1）断奶体重（WWL），2）周岁体重（YWL），3）周岁体重和肌肉评分指数（IXL）。第四个品系是未选择的对照品系（CTL）。观测值数量从1699（CTL）到2811（WWL）不等，系谱文件中的动物数量从2266到3192不等。使用两种动物模型，通过平均信息法采用REML来获得估计值。模型1包括随机直接遗传效应和母体遗传效应、母体永久环境效应以及残余环境效应，以及固定的性别×年份效应。模型2还包括随机祖母遗传效应和祖母永久环境效应。对于出生体重，模型1和模型2得出的直接遗传力和母体遗传力估计值，以及母体永久环境效应所导致的方差比例几乎相同。仅能获得IXL（0.03）和CTL（0.01）的祖母遗传力估计值。对于断奶体重，两个模型得出的直接遗传力估计值相似。模型1得出的母体遗传力估计值对于WWL、YWL、IXL和CTL分别为0.18、0.20、0.13和0.20，模型2对应的估计值分别为0.34、0.31、0.13和0.34。对于IXL，无法获得由祖母遗传效应和祖母永久环境效应所导致的方差估计值，并将其设为零。WWL、YWL和CTL的祖母遗传力估计值分别为0.05、0.09和0.12。WWL、YWL、IXL和CTL的直接遗传效应与母体遗传效应之间的相关估计值分别为-0.13、-0.44、-0.11和-0.26。WWL、YWL和CTL的直接遗传效应与祖母遗传效应之间的相关估计值分别为0.21、0.83和0.55，母体遗传效应与祖母遗传效应之间的相关估计值分别为-0.99、-0.8-4和-0.76。这些结果表明，祖母效应对于断奶体重可能很重要，如果模型中不包括祖母效应，母体遗传力可能会被低估。
