Deriving Economic Values for Reaction Norms of Growth in Pigs

Slopes of reaction norm models, also called reaction norms (RN), are alternative traits used in animal breeding for selection of genotypes that perform more consistently across a range of environments. Environmental sensitivity is of economic importance when the environment where selection takes place differs considerably from the commercial environment of slaughter pigs. The position on the environmental trajectory where intercept of reaction norm models is defined influences the economic values (EV) for slope and intercept. This position has to correspond to the trait definitions of intercept and slope of reaction norm models used to estimate variance components. The magnitude of EV for RN depends on the difference between the selection and production environments and the EV for the trait of interest. Economic values for RN may be negative or positive depending on whether the production environment is below or above the selection environment. Non-linear EV for growth across the environmental trajectory had minimal impact on the EV for RN of growth. Further genetic and economic analyses of extensive industry data are required to better quantify the economic importance of RN in pig breeding.