Genomic predictions for dairy calf health traits

Abstract

Healthy calves are important to the productivity and welfare of dairy herds. They are potential herd replacements as well as a source of livestock trading income. Further, healthy calves are important to the continuous improvement of animal welfare that is valued by farmers and consumers. In our dataset of ~20,000 calves with health records, the prevalence of stillbirth, preweaning mortality and scours was 4%, 2% and 6% respectively suggesting that there are opportunities to improve calf health. The aim of this study was to estimate variance components for novel calf traits and gather the perspectives of farmers about the relative importance of these traits. Univariate linear models that included a genomic relationship matrix were used to estimate variance components for stillbirth, preweaning mortality, scours, respiratory disease and calf vitality where heritability (h²) estimates ranged from 1% to 11% depending on the trait. Calf vitality is a new, subjectively-scored trait where farmers describe calves on a scale from A (vigorous) to E (dead). The models included herd-year-season, sex, parity group and calving ease as fixed effects and these were found to be significant for most breed and trait combinations. Our survey found that calf traits were valued by farmers similarly to cow survival. They preferred new traits to be published separately, rather than in multi-trait indexes. As genetic variation in several calf health traits was measured and the value to farmers has been tested, we conclude that there is an opportunity to introduce new traits into routine evaluations that target genetic gain for calf health.