Genetic correlations between steer and heifer, and between environments for measures of growth and live body composition in two tropical genotypes

The theory relating genetic difference between the sexes, genotype x sex interaction and thegenetic correlation between the sexes is described by Eisen and Legates (1966), wheregenotype x sex is considered a special case of genotype x environment interaction. It followsfrom this that a genetic correlation of less than one between the sexes is evidence both ofgenotype x sex interaction and of genetic difference between the sexes. By extension, this alsoholds for similar traits in different environments. Here, we present genetic correlations forcorresponding measures of steer and heifer growth and live body composition for two tropicalgenotypes that are important to beef production in tropical and sub-tropical Australia. The dataare from a project described by Burrow et al. (2003). The correlations provide insight into thepossible magnitude of genotype x environment and genotype x sex interactions whenenvironments differ markedly for the sexes. As in industry, steers were run in a more benignenvironment and finished in a feedlot, while heifers were run in typically harsher, tropicalenvironments.