Evaluation of a Linearized Type Appraisal System for Holstein Cattle

Abstract

Data from a Holstein linear type appraisal project for traits suggested by the National Association of Animal Breeders [USA] were analyzed to evaluate genetic statistics of linear type. Data were scored by 28 classifiers as an adjunct to the regular Holstein Association classification program. Average scores for 14 linear traits (Scored 50-99) ranged from 72.3-79.6 points. Stage of lactation, age at classification, sire, classifier-herd sublcass and interaction of age by classifier were important sources of variation for most traits. Heritabilities were from 0.12 (rear view legs and suspensory ligament)-0.32 (stature). Phenotypic correlations ranged from -0.29-0.76, with the larger correlations among udder traits. Genetic correlations were generally of the same sign and larger than corresponding phenotypic correlations. Linear scoring permitted interpretation of biological relationships among conformation traits. Heritabilities for linear traits were comparable to corresponding traits scored in relation to an ideal. Increased classifier experience with linear scoring may result in larger heritability because of decreased residual variation.