Investigation of genotype × production environment interaction for weaning weight in the Santa Gertrudis breed in Australia

Abstract

Weaning weight records of 12 563 Santa Gertrudis calves were used to estimate (co)variance components using a bivariate restricted maximum likelihood analysis. The analysis considered measurements on animals born in favourable production environments as Trait 1 and animals born in unfavourable production environments as Trait 2. Estimates of variance components for weaning weight across production environments were similar in magnitude. An additive genetic correlation of 0·64 between production environments was significantly different from unity, suggesting that there was a genotype production environment interaction. However, when a sire contemporary group interaction effect was included in the model, the genetic correlation between Trait 1 and Trait 2 was not significantly different from unity. These results suggest that the ranking of Santa Gertrudis sires across production environments was caused by changes in ranking from one contemporary group to the next rather than changes in ranking across production environments.