Estimation of additive and non-additive genetic parameters for carcass traits on bulls in dairy, dual purpose and beef cattle breeds

Carcass records on 4749 bulls (from 153 sires) slaughtered at an average age of 20 months were collected from slaughter houses in the Netherlands. Bulls had a variable proportion of genes from Dutch Black and White (DBW), Dutch Red and White (DRW) and Pimontese (PIM). Additive genetic and crossbreeding parameters were estimated for fleshiness score (FLESH), fat covering score (FAT) and carcass weight (CWT) using three fixed models (additive breed, Dickerson and Kinghorn model) and the corresponding three mixed models with random sire effects. These models involved additive breed, heterosis (or dominance), and recombination loss (or epistatic loss) effects (i.e., crossbreeding parameters) as regression covariates. In addition, an additive sire group model was used as a mixed model. FLESH and FAT were defined numerical values ranging from 1 (poorly muscled; very much fat) to 15 (very muscled; very little fat). When comparing models, estimates of crossbreeding parameters over breeds and breed combinations showed similar patterns, although absolute values between the same parameters differed up to a standard error between fixed and mixed models and between Dickerson and Kinghorn models. Mixed models showed larger standard errors relative to fixed models. Relative to DBW, PIM showed significantly positive favorable breed effects for FLESH (ranging from 5.8 to 6.3 for different models) and CWT (62.6 to 111.8 kg), and unfavorable for FAT (-1.7 to -2.6). DRW showed favorable, bur, smaller than PIM, additive genetic effects for all three traits (2.2 to 2.3 for FLESH, 0.1 to 0.3 for FAT and 18.1 to 24.2 kg for CWT). Significant heterosis was only found for FAT (0.4 to 0.7) and for CWT (12 to 14 kg) in the cross DBW x DRW. Significant recombination and epistatic effects were obtained for CWT in the Dickerson and the Kinghorn models Models not including non-additive effects over-estimated genetic variances and heritabilities for FLESH and FAT. (C) 1998 Elsevier Science B.V. All rights reserved.