Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Univariate and multivariate parameter estimates for milk production traits using an animal model. II. Efficiency of selection when using simplified covariance structures | Genet Sei Evol 1992 24 431-447 Elsevier INRA 431 Original article Univariate and multivariate parameter estimates for milk production traits using an animal model. II. Efficiency of selection when using simplified covariance structures PM Visscher1 WG Hill1 R Thompson2 1 University of Edinburgh Institute of Cell Animal and Population Biology West Mains Road Edinburgh EH9 3JT 2 AFRC Institute of Animal Physiology and Genetics Research Roslin EH25 9PS Midlothian UK Received 5 August 1991 accepted 3 June 1992 Summary - The effect of simplifying covariance structures for milk fat and protein yield in lactations 1-3 on accuracy of selection for lifetime yield was investigated using selection index theory. Previously estimated co variances were assumed to be the true population parameters. A modified repeatability model ie assuming a genetic correlation of unity between performances across lactations but allowing for different heritabilities and variances in different lactations was used to investigate the efficiency of selecting sire on their progeny performance. For most combinations of heritabilities in first and later lactations selecting sires using the repeatability model was nearly 100 efficient in terms of accuracy of selection compared to a general multivariate model. The predicted response to selection using a modified repeatability model was approximately 10 too high. It was found that applying a transformation to make new traits in lactation 1 uncorrelated at the phenotypic and genetic level to milk fat and protein yield in later lactations and assuming that 3 new uncorrelated variates were formed was highly efficient in terms of accuracy of selection when compared to the accuracy of a general multivariate model. This transformation was recommended for a national BLUP evaluation since it may take account of selection to a larger extent than when performing separate analyses for milk fat and protein yield. dairy cattle milk production selection index genetic .
