Cue R I, Hayes J F
J Dairy Sci. 1985 Feb;68(2):374-81. doi: 10.3168/jds.S0022-0302(85)80834-1.
Multitrait restricted maximum likelihood methods were used to estimate heritabilities of direct and maternal effects for calving ease and their genetic correlation for heifers and cows. Heritabilities were 4.9% for direct effects and 4.8% for maternal effects of heifers and 1.1% and .7% for cows. Genetic or direct maternal correlations were--.40 in heifers and .07 in adult cows. Restricted maximum likelihood methods also were used to estimate the genetic correlation (.995) between direct effects for calving ease measured in heifers and in cows.
采用多性状约束最大似然法估计了产犊难易度直接效应和母体效应的遗传力，以及小母牛和母牛的遗传相关性。小母牛直接效应的遗传力为4.9%，母体效应的遗传力为4.8%；母牛直接效应的遗传力为1.1%，母体效应的遗传力为0.7%。小母牛的遗传或直接母体相关性为-0.40，成年母牛为0.07。约束最大似然法还用于估计小母牛和母牛产犊难易度直接效应之间的遗传相关性（0.995）。
