Using cow carcass weight to select efficient cows in UK

Abstract

Breeding more efficient cows is important for both increased profitability and reduced environmental impact. Therefore, there is a need to estimate genetic merit for feed intake of cows. While direct measurement of feed intake is difficult, maintenance requirements which accounts for one third of the energy intake of a cow, can be adequately approximated using body weight. Mature cows are not usually weighed, but abattoirs do collect carcass weights of cull cows. Carcase weight varied between 268 kg and 400 kg. Heritability estimates of carcass weight, conformation and fat class of mature cows were calculated. Mature cows between 1 095 and 7 301 days of age were included in the study. A total of 4 721 cows with weight phenotypes were included, born between 1997 and 2020. A mixed linear animal model was fitted considering the cow, parity of the cow’s dam, number of calvings per cow, breed and season of birth as fixed effects and coefficient of heterosis and recombination loss estimated from four breed groups as covariate effects. The study cows were traced back up to five generations in the pedigree that include 67 641 animals in total. The heritability estimates were generated using ASReml. The estimated heritabilities were 0.64 ± 0.01, 0.49 ± 0.10 and 0.44 ± 0.01 for carcass weight, carcass fat and conformation, respectively. The moderate to high heritability estimates observed in this study indicates there is cull cow carcass weight genetic variation to allow for genetic improvement and that when data for direct feed intake is limited, this trait in the meantime could be used as a proxy for cow feed intake and consequently, predicted methane emissions.