Genetic Parameters of Foot and Leg Traits in Future AI Bulls: I. Influence of Age at Recording and Classifier

Abstract

Information on foot and leg traits was collected on 8494 young potential future AI bulls of the three populations Danish Red, Danish Friesian and Danish Jersey by two classifiers between 1985 and 1996. Each animal was assessed at 5 and 10 months of age. The data set was used to examine the influence of age and classifier on genetic parameters of foot and leg traits by treating traits recorded at two different times or by two different people as a different characteristic in a bivariate analysis. The general incidence of foot and leg diseases was very low in young animals: only interdigital dermatitis, heel necrosis and solar bruising showed a frequency higher than 2% in 10-month-old bulls. The same traits measured on different claws yielded very high genetic correlations (rg 0.77-0.98), suggesting that the number of measurements could be reduced. Hooves increased in size with age, and the genetic correlation between the two age classes was high (rg 0.60-0.77). The agreement between classifiers was very high for objectively measured traits, especially for the younger age class, and interdigital dermatitis and heel necrosis, but inconclusive for the subjectively scored characteristics.