Genetic and Phenotypic Parameters of Longevity in Australian Dairy Cattle

Abstract

A new method of evaluating cows for longevity based on survival scores (Si is presented. Survival is defined as Si = 1 if the cow survives from i to i + 1 yr after first calving, or Si = 0 if the cow does not. Herd Improvement records on 253,000 AI-bred cows were used to calculate survival scores, and the genetic and phenotypic parameters of these scores were examined. Survival was constant at .85 to .86 until S4 after which it declined. Average productive life was 5.8 to 6.6 yr, which is consistent with other Australian estimates. Heritability of survival was low (.004 to .088), especially for S1 and S2. Genetic correlations among survival scores was highest in early years (up to S4), and f..