Slaughter and carcass traits of calves from first-cross and reciprocal back-cross beef cows

Breed-of-dam and sex-of-calf effects are reported based on observation of 2007 heifer and steer carcasses. The carcasses were derived from Limousin-sired calves born to dams representing 15 F 1 and backcross genotypes reared at two locations over a period of 5 yr. The calves represented Hereford × Angus, Charolais × Shorthorn, Simmental × Shorthorn and all backcross combinations involving Charolais or Simmental with Hereford, Angus or Shorthorn. Carcass traits were analyzed on an unadjusted, a constant hot-carcass weight, and a constant rib-fat depth basis. The slaughter criteria dictated that steers were heavier at slaughter than heifers. They also exhibited higher dressing yield, greater longissimus thoracis area, and lower fat depth. Charolais and Simmental breeding was associated with less rib fat depth, greater longissimus thoracis area, a higher proportion of preferred cuts, less dissectible fat, more bone and more lean in the preferred cuts than British beef breeding. Within the European (Charolais and Simmental) and British beef (Hereford, Angus and Shorthorn) breed groups, breed effects were smaller, but for carcass composition traits they were frequently significant. When compared with Simmental, Charolais breeding tended to be associated with less marbling, less rib fat depth, less dissectible fat and more lean in the preferred cuts. Among the British beef breeds, Hereford was associated with the highest proportion of preferred cuts, Shorthorn with the lowest rib fat depth — but the highest dissectible fat — and Angus with the most marbling, the greatest longissimus thoracis area and the lowest bone content. This research has demonstrated that breed effects for carcass composition traits tend to be additive and that a significant effect may be associated with substitution of as little as one-eighth of the breed composition. Key words: Beef cattle, slaughter traits, carcass traits, breed type, crossbred dam, backcross dam