The objective ofthis study was to evaluate differences in sire genetic values obtained by aconventional animal model (AM) and by a reaction norms hierarchical model (RNHM)that considers the genotype by environment interaction. A total of 25,500 recordswas used collected by PROMEBO - beef cattle improvement program of the NationalBreeders Association "Herd Book Collares" on Devon cattle born from 1980 though2005. Post weaning gain 345 adjusted (PWG345) was the evaluated trait and theINTERGEN program was employed for data analysis. Reaction norms of the 25 sireswith larger offspring showed ranking exchanges and scale effect in the environmentalgradient. Spearman rank correlations between genetic values obtained by AM andRNHM at low, medium and high environmental levels were used to assess selectiondecision based on the different models. These correlations ranged from 0.12and 0.99, therefore showing substantial changes in ranking, particularly betweenthose genetic values obtained by the RNHM at low level compared to the sameRNHM at medium and high levels and to AM, when considering the top 5% bulls.The results indicated that the selection process should consider the genotypeby environmental interaction to maximize genetic gain and production of thispopulation in each specific environment.
