Evaluating dairy sires for conformation of their daughters: use of first classification records

Abstract

Type classification records for 18 132 Australian Holstein-Friesian heifers were analysed. These consisted of 27 traits scored in three or six categories, from three rounds of classification between 1981 and 1983. Only first lactation, first classification records were considered. The model of analysis included herd-round-classifier subclasses as fixed and sires as random effects, fitting age at classification as a linear and quadratic covariable within subclasses. Herd-round-classifier effects explained between 18% and 37% of total sums of squares. Age accounted for 5.8-2.4% for traits related to body size and for 1.6% or less for the other traits. Heritability estimates obtained using a Restricted Maximum Likelihood procedure ranged from 0.44 for total score, 0.42 for stature and 0.40 for dairy character, to 0.10 or less for feet and legs, rear heel, rear legs set, bone quality and rear teat placement. On average, values were higher than corresponding 'all-lactation' estimates. Covariance components between all traits were obtained. The resulting genetic variance/covariance matrix was then forced to be positive semi-definite before calculating genetic and phenotypic correlations. Breeding value estimates for all sires and traits were determined using a univariate Best Linear Unbiased Prediction procedure for the above model. In addition, the relationship matrix between males was incorporated. There were 2 597 sires with an average of 23.2 effective daughters, and 474 sires without daughter records included as male ancestors. The association between breeding value estimates for different traits was examined by multiple regression. Sire-son regressions were determined and compared with their expectations. Australian Breeding Values for production were obtained for a subset of sires and contrasted to the type proofs. There seemed to be little correlation between genetic merit for type and milk production.