Genetic Evaluation of Carcass Traits: Looking at the Effects of Slaughter End Points

An exhaustive review of estimates of heritability (h) for a broad spectrum of beef production traits published in the scientific literature from 1945 to 1991 was conducted by Koots et al. (1994), but their review did not include other important carcass traits (e.g., kidney, pelvic, and heart fat percentage, yield grade, fat weight) and due to the purpose of their study, individual estimates of h for the traits reviewed were not reported, but only the weighted and unweighted averages. On the other hand, the review by Marshall (1994) reported estimates of h for some additional carcass traits, but only for cattle reared under U.S. conditions and, basically, estimates presented were on an age-constant basis. In addition, due to few estimates for the additional traits at that time, averages of estimates of h for several carcass traits were based on only one to three observations. Neither of the two reviews focused on the effect of end point on estimates of h. In the last ten years, as a consequence of the increased interest of many beef producers on carcass yield and quality to satisfy consumer demand, numerous studies of carcass traits have published estimates of h and genetic correlations (rg), doubling, at least, the number of estimates for many carcass traits. This review was conducted to present estimates of h and rg for carcass traits published in the scientific literature from 1962 to 2004. Because animals are slaughtered at, or carcass traits are adjusted to, different end points, the effects of adjusting for age, weight or fat depth on such estimates are also discussed.