Multivariate analyses of carcass traits for Angus cattle

9 Multivariate analyses of carcass traits for Angus cattle, consisting of 6 traits recorded 10 on the carcass and 8 auxiliary traits measured by ultra-sound scanning of live animals, 11 are reported. Analyses were carried out by restricted maximum likelihood, fitting a 12 number of reduced rank and factor-analytic models for the genetic covariance matrix. 13 Estimates of eigen-values and -vectors for different orders of fit are contrasted and 14 implications on the estimates of genetic variances and correlations are examined. 15 Results indicated that at most 8 principal components were required to model the 16 genetic covariance structure among the 14 traits. Selection index calculations sug17 gested that the first 7 of these PCs sufficed to obtain estimates of breeding values for 18 the carcass traits without loss in expected accuracy of evaluation. This implied that 19 the number of effects fitted in genetic evaluation for carcass traits can be halved by 20 estimating breeding values for the leading principal components directly. 21