Vinson W E
Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061.
J Dairy Sci. 1987 Nov;70(11):2450-5. doi: 10.3168/jds.S0022-0302(87)80308-9.
Evidence is reviewed that indicates substantial differences among herds in variation for production traits in dairy cattle. Examples are given to illustrate the overevaluation and selection of higher proportions of individuals from more variable herds, which reduces response to selection if greater variability is not due in part to greater additive genetic variance. Differences in heritability according to herd mean and variance are examined. Potential bias is substantial in genetic evaluations of cows and may increase over generations where, if the model is realistic, evaluations of dams are used in evaluations of daughters. Possible methods of adjustment are discussed.
本文回顾了相关证据,这些证据表明奶牛群体在生产性状变异方面存在显著差异。文中给出了一些例子,用以说明从变异更大的群体中过度评估和选择更高比例个体的情况,如果更大的变异性并非部分归因于更大的加性遗传方差,那么这会降低选择反应。研究了根据群体均值和方差得出的遗传力差异。在奶牛的遗传评估中,潜在偏差很大,并且在多代中可能会增加,在这种情况下,如果模型符合实际情况,那么在女儿的评估中会使用母亲的评估结果。文中讨论了可能的调整方法。