Dodenhoff J, Van Vleck L D, Gregory K E
Department of Animal Science, University of Nebraska, Lincoln 68583-0908, USA.
J Anim Sci. 1999 Apr;77(4):840-5. doi: 10.2527/1999.774840x.
Weaning weights from nine parental breeds and three composites were analyzed to estimate variance due to grandmaternal genetic effects and to compare estimates for variance due to maternal genetic effects from two different models. Number of observations ranged from 794 to 3,465 per population. Number of animals in the pedigree file ranged from 1,244 to 4,326 per population. Two single-trait animal models were used to obtain estimates of covariance components by REML using an average information method. Model 1 included random direct and maternal genetic, permanent maternal environmental, and residual environmental effects as well as fixed sex x year and age of dam effects. Model 2 in addition included random grandmaternal genetic and permanent grandmaternal environmental effects to account for maternal effects of a cow on her daughter's maternal ability. Non-zero estimates of proportion of variance due to grandmaternal effects were obtained for 7 of the 12 populations and ranged from .03 to .06. Direct heritability estimates in these populations were similar with both models. Existence of variance due to grandmaternal effects did not affect the estimates of maternal heritability (m2) or the correlation between direct and maternal genetic effects (r(am)) for Angus and Gelbvieh. For the other five populations, magnitude of estimates increased for both m2 and r(am) when estimates of variance due to grandmaternal effects were not zero. Estimates of the correlation between maternal and grandmaternal genetic effects were large and negative. These results suggest that grand-maternal effects exist in some populations, that when such effects are ignored in analyses maternal heritability may be underestimated, and that the correlation between direct and maternal genetic effects may be biased downward if grandmaternal effects are not included in the model for weaning weight of beef cattle.
对九个亲本品种和三个合成品种的断奶体重进行了分析，以估计由于祖代母本遗传效应引起的方差，并比较两种不同模型下由于母本遗传效应引起的方差估计值。每个群体的观测数从794到3465不等。每个群体系谱文件中的动物数量从1244到4326不等。使用两个单性状动物模型，通过平均信息法的REML来获得协方差成分的估计值。模型1包括随机的直接遗传、母本遗传、永久性母本环境和残余环境效应，以及固定的性别×年份和母牛年龄效应。模型2还包括随机的祖代母本遗传和永久性祖代母本环境效应，以考虑母牛对其女儿母本能力的母本效应。在12个群体中的7个群体中获得了由于祖代母本效应引起的方差比例的非零估计值，范围从0.03到0.06。在这些群体中，两种模型下的直接遗传力估计值相似。由于祖代母本效应引起的方差的存在，并没有影响安格斯牛和吉尔维牛的母本遗传力（m2）估计值或直接遗传效应与母本遗传效应之间的相关性（r(am)）。对于其他五个群体，当由于祖代母本效应引起的方差估计值不为零时，m2和r(am)的估计值幅度都增加了。母本遗传效应与祖代母本遗传效应之间的相关性估计值很大且为负。这些结果表明，在一些群体中存在祖代母本效应，在分析中如果忽略这些效应，母本遗传力可能会被低估，并且如果在肉牛断奶体重模型中不包括祖代母本效应，直接遗传效应与母本遗传效应之间的相关性可能会向下偏差。
