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Effects of age, weight and fatness slaughter end points on estimates of genetic parameters for carcass traits
The influence of slaughter end points of age, carcass weight and fat thickness (covariates) on estimates of phenotypic variances ( s2p ), heritabilities (h2) for, and genetic correlations (rg) among, 14 carcass traits of purebred and composite steers from 12 breeds was studied. In addition, the effects of different levels of fat thickness and hot carcass weight as end points on estimates of breed effects and retained heterosis (individual and maternal combined) were also examined. Parameters were estimated by REML using animal models. In general, estimates of s2p and h2 for carcass traits indicate that enough phenotypic and genetic variation exist to change measures of carcass merit by single-trait selection. For some carcass traits, however, the magnitude of change would depend on the effect of slaughter end point as estimates of s2p and h2 were often different for different end points. The largest differences in estimates of h2 with different end points were for hot carcass weight and retail product weight. Among all parameters estimated, the greatest effects of end points were on estimates of r g for 54 of the 91 pairs of traits, which in some cases not only changed in magnitude (0.15 or more), but also in sign. Therefore, expected correlated responses to selection would also differ depending on end point. Ranking of breeds and expression of heterosis also varied for many carcass traits depending on slaughter end points. As an example, the estimate of retained heterosis for actual retail product as a percentage of hot carcass weight for the MARC III composite breed was significantly negative (-1.27%) at 0.7 cm, but was significantly positive (2.55%) at 1.5 cm of fat thickness. Furthermore, some estimates of heterosis also doubled in magnitude depending on levels of fat thickness end point. Age, weight and fatness end points influenced the sign and(or) the magnitude of estimates of genetic parameters for several carcass traits. ^
Agriculture, Animal Culture and Nutrition|Biology, Veterinary Science
Rios-Utrera, Angel, "Effects of age, weight and fatness slaughter end points on estimates of genetic parameters for carcass traits" (2005). ETD collection for University of Nebraska - Lincoln. AAI3194125.