|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 1998
Publication Date: N/A
Technical Abstract: Carcass traits of beef cattle can be expressed on age, weight, or fatness constant basis. These definitions imply that a measured trait could be considered as three traits with different heritabilities and with genetic correlations among the traits. Carcass measurements of 1,292 steers sired by 409 Shorthorn sires were analyzed with REML. The models and measurements sfor the three subtraits were the same (herd, year, kill group) except for the linear covariates of slaughter age (336 to 865 d), hot carcass weight (220 to 477 kg), and fat depth at 12th rib (0 to 28 mm) with the subtraits denoted in that order. The estimates of genetic correlations between subtraits 1 and 2, 1 and 3, and 2 and 3 were: dressing percent, .99, .63, .64; kidney-pelvic-heart fat percent, .81, .64, .97; marbling score, .80, .66, .98; and ribeye area (cm2), 1.00, .97, .97. Heritability estimates were also different for the subtraits even though the measured records were ethe same: dressing percent, .60, .56, .70; KPH, .53, .39, .33; marbling, .53, .37, .32; and ribeye area, .55, .56, .33. Environmental correlations ranged from .49 to 1.00 depending on trait and subtraits. Phenotypic variances were the largest based on fat depth except for dressing percent. These results based on a relatively small sample suggest that some carcass traits when adjusted for age, weight, or fat thickness should be considered different traits. Conversion of estimated progeny differences from one basis to another can be done with estimates of genetic correlations and heritabilities for the subtraits.