Genotype by Environment Interactions for Average Daily Gain Using Multiple-Trait Analyses in Australian Pigs

Abstract

Data comprised of 265,103 records on pigs from nine herds collected from 2000 to 2010 were used to investigate whether genotype by environment interactions (GxE) existed for average daily gain (ADG) of pigs. Least squares means for herd by birth month from an animal model were used to quantify environmental conditions of contemporary groups. The environmental trajectory was divided into two, three or seven groups for alternative trait definitions of ADG considered to be a distinct trait for each environmental group. A multi-trait approach was used to investigate GxE. Heterogeneity of additive genetic variance and heritabilities were found for ADG between environmental groups when the environmental trajectory was divided into three or seven groups. Heritability estimates were highest for the intermediate environmental group (0.22±0.01) and reduced continuously to 0.15±0.02 for lower environmental groups. Estimated common litter effect did not differ significantly between trait definitions of ADG. Genetic correlations between ADG observed in different environments varied from 0.61±0.16 to 0.99±0.02. Genetic correlations were less than 0.80 when ADG was observed in two environments that differed by more than about 60 g/day indicating existence of significant GxE for ADG in pigs. At least 200 common sires were required to achieve statistical significance of these genetic correlations, demonstrating that large data sets with good data structures are required to detect GxE.