Genetic evaluation of longevity in Italian Jersey

Longevity in animal science is a complex trait that can be approached in different ways. So far, for the Italian Jersey population, no official selection index is being applied. Thus, the present study aims to investigate the feasibility of an official routine genetic evaluation for longevity in this population. Longevity was analysed as stay-ability, meant as the ability of cows to survive to a specific calving event. Calving records for 20,724 cows were analysed. Phenotypically, longevity showed an average of 2.65 ± 1.62 lactations. Heritability was estimated with an animal model, which included the random effect of the contemporary group and the random animal additive genetic effect, fitted using a pedigree-based relationship matrix. Heritability estimates ranged from 0.050 ± 0.012 to 0.208 ± 0.022 for stay-ability traits, depending on the model. Stay-ability at the 4th lactation has been chosen to be the breeding objective, i.e. the minimum number of lactations a cow should show to have a successful productive life. Furthermore, genetic and phenotypic correlations between stay-ability and other traits undergoing selection such as milk, fat and protein yield, fat and protein percentage, type traits (e.g. foot angle, fore udder attachment, rear udder height, udder support, udder depth) and age at first calving (AFC) were estimated for cows’ population. Generally, stay-ability showed a high genetic correlation with production traits, fore udder, rear udder height, udder support and foot angle, while it was negligible with AFC. Longevity, as stay-ability, could be considered for routine genetic evaluations for the Italian Jersey population.