ESTIMATES OF HERITABILITIES OF CANADIAN HOLSTEIN CONFORMATION TRAITS BY THRESHOLD-MODEL

Sire variances for 30 conformation traits on Canadian Holsteins were estimated on the underlying continuous scale using a single trait threshold linear model. Data were linearized first classifications on 66 617 cows by 3305 sires, classified since February 1988. The model included a random sire effect and fixed effects of herd-round of classification-classifier, age at classification and stage of lactation at classification. Sires were assumed unrelated in this study. Variance components for sires were estimated by REML EM algorithm. Estimates of heritabilities were generally larger than those currently used in genetic evaluation for type traits in Canadian Holstein population. The new heritabilities are recommended for use in a traditional linear animal model procedure.