Genotype x environment interactions identified in southern Australian beef production

Abstract

Data from the “Southern Crossbreeding Project” were utilised for the analysis of genotype by environment (G x E) interactions in a southern Australian production system. “Domestic heifers” were slaughtered for the domestic market at an average of 16 months (218kg Hot Standard Carcass Weight and 9.7mm rump fat at the P8 site) whilst “Export steers” were slaughtered for the export market at an average of 23 months (323kg HSCW and 14.7mm P8 fat). Performance of each sex was treated as a separate trait to assess the interaction between carcass traits at different market end points. Data were analysed using a univariate animal model containing the fixed effects of sex, sex x breed and sex x management group. Traits other HSCW were analysed on a weight constant basis by fitting HSCW x sex as a fixed effect. The random effects were animal (pedigree) for each sex resulting in a genetic variance for each sex and the correlation between heifers and steers (3 genetic and 2 residual variance components). For all carcass traits, the genetic correlation between market end points was less than one, although only significantly so for loin eye muscle area. It is not possible to determine the extent to which the significant interaction was the result of different weight endpoints, ages or differences between heifers and steers.