Genotype × environment interaction effects on carcass traits in Japanese Black cattle

The importance of genotype × environment (region or management system) interactions for carcass traits in Japanese Black cattle was investigated using both univariate and multivariate animal models. The univariate approach was used mainly to test the significance of interaction effects. The multivariate approach was used to estimate genetic correlations, which indicated the magnitude of genotype × environment (GE) interactions. The more a genetic correlation deviates from 1, the larger the interaction. From the univariate approach, the addition of genotype × environment (region or management system) interaction (co)variance components resulted in an improved fit of the model for all traits in both cases (P < 0.001). However, estimates of genetic correlation between regions obtained from the multivariate approach for hot carcass weight, LM area, rib thickness, s.c. fat thickness, and marbling score were 0.97, 0.95, 0.93, 0.97, and 0.93, respectively. The corresponding estimates between management systems were 0.84, 0.92, 0.84, 0.90, and 0.97, respectively. These results indicate that GE interaction effects on carcass traits of Japanese Black cattle may be biologically unimportant. Therefore, breeding values obtained using the multivariate method would rank sires similarly in all environments. Consequently, carcass traits measured in these two different regions or management systems can be treated as the same traits.