Genetic parameters for longevity measures in Brazilian Holstein cattle using linear and threshold models
Abstract. The aim in this study was to estimate variance components and heritability of different longevity measures related to productive life and survival at a specified age, using linear and threshold models, to specify the more appropriate measure to express longevity in Brazilian Holstein cows. Production and reproduction records of Holstein cows were collected from 1991 to 2010, for cows born between 1987 and 2006. Variance components were obtained by restricted maximum likelihood (REML) for measures of productive life and a Bayesian analysis for survival measures. The heritability estimates for longevity measures ranged from 0.06 to 0.09, using the linear model and from 0.05 to 0.18 for traits using the threshold model. This suggests an inexpressive genetic gain using selection for these traits, whereas improvements in environmental factors which affect these animals may lead to greater phenotypic gains. Survival up to 48 months from first calving was the measureing point defined as the most appropriate to be included in future official genetic evaluations of Holstein cattle in Brazil.