Analysis of genotype by feeding level interaction in pigs applying reaction norm models

Progeny groups of sires may differ in their ranking for growth performance at different feed intake levels leading to genotype by feeding level (GxFL) interactions. In pig breeding, GxFLinteractions have been demonstrated in selection experiments (eg Cameron and Curran 1995).In addition, Hermesch et al. (2002) showed that feed intake level affected genetic parametersfor performance traits in pigs.Reaction norm models have been used in the analysis of genotype by environment interaction(eg Kolmodin et al. 2002; Pollott and Greeff 2004). These models describe the performanceexpressed by a genotype as a function of the environment. Often the specific environment isdescribed by the mean performance of animals, which is affected by underlying environmentalfactors as well as genotype of the animals. Allocation of litter mates across feeding levelsreduces this confounding somewhat and provides genetic linkage between feeding levels.These data allow the analysis of GxFL interaction. Estimating the response of sire progenygroups to changing feed intake levels provides additional information to conventionalperformance traits, which may lead to improved selection strategies for efficient lean meatgrowth. It was the aim of this study to estimate GxFL interaction in pigs through applyingreaction norm models which were compared with standard sire models.