GENOTYPE ENVIRONMENT INTERACTION IN PIG BREEDING PROGRAMS - METHODS OF ESTIMATION AND RELEVANCE OF THE ESTIMATES

In pig breeding programmes breeding values for growth and carcass traits are generally estimated in test environments, e.g. central test or on-farm test. The breeding goal, however, should be defined at the level of commercial growing. Genotype .times. environment (G .times. E) interaction (test and commercial environment) will lower the efficiency of a breeding scheme bases on testing in test environments. The effect of G .times. E interaction on the response to selection can be examined by interpreting the interaction as a genetic correlation between a trait measured in one environment and a similar trait in another environment. Here, two types of genetic correlation need to be considered: rG for the correlation between test and commercial environment, and rg, for the correlation among various commercial environments. In this paper procedures to estimate these genetic correlations are reviewed. Furthermore, some testing strategies are compared in model calculations. The objective was to determine at which (low) levels of rG testing of individuals, sibs or progeny in commercial environments is more efficient than testing in a test environment. It is concluded that generally central testing is to be perferred and that additional testing of sibs in commercial environments may be of value.