Investigation into the presence of genotype by environment (G×E) interactions in scottish blackface lamb weaning traits

Abstract

Genotype by environment interactions (G×E) can form a potential source of inefficiency in animal breeding if selection decisions are made without acknowledging their effects. The presence of such interactions between two Scottish hill farms was investigated using performance data from 16,867 Scottish Blackface lambs collected between 1997 and 2009. Pedigree information was available for 25,970 animals and 24 of the sires used during this time period were used on both farms. Farm A is located on the East Coast of Scotland, whereas Farm B is on the West Coast. The farms differ in a number of aspects including annual rainfall, topography, vegetation, temperature and altitude ranges, with Farm B representing a harsher environment overall. Traits studied were lamb weight (LWT), ultrasound backfat depth (UFD) and ultrasound muscle depth (UMD) at weaning. To determine the level of G×E present for these traits, genetic correlations were estimated for each trait between the two farms. Heritabilities and correlations were estimated using univariate and bivariate analyses in ASREML based on a model that fitted relevant fixed effects and both direct genetic and maternal permanent environmental (c2) random effects. Moderate heritabilities, at each farm, were estimated for all traits; LWT-Farm A = 0.21 (0.03), Farm B = 0.27 (0.03); UFD-Farm A = 0.21 (0.02), Farm B = 0.26 (0.03); UMD-Farm A = 0.32 (0.03), Farm B = 0.35 (0.03). Estimates of c2 were low to moderate; LWT-Farm A = 0.16 (0.01), Farm B = 0.18 (0.02); UFD-Farm A = 0.09 (0.01), Farm B = 0.12 (0.01); UMD-Farm A = 0.08 (0.01), Farm B = 0.12 (0.01). Genetic correlations estimated between the two farms were not significantly different from 1. The lack of significance would suggest that no G×E exists for weaning weights or ultrasound tissue depths between the two farms in this study.