Genotype X Environment Interaction For Growth And Reproduction Traits Of Composite Beef Cattle In Brazil

Brazil has a great diversity of beef cattle production systems due to climatic, geographic, cultural and economic factors (Eler, J.P., Ferraz, J.B.S., Golden, B.L. et al. (2000); Toral, F.L.B., Silva, L.O.C., Martins, E.N. et al. (2004); Lopes, J.S., Rorato, P.R.N., Weber, T. et al. (2008)). The evaluation of genotype x environment interaction (GxE) is, therefore, relevant to breeding programs, since the best animals in a given environment, may not have the offspring of better performance when it is raised under a different environment than that their parents were selected. According to Alencar, M.M., Mascioli, A.S. and Freitas, A.R. (2005), this interaction may also cause changes in genetic, phenotypic and environmental variations and therefore result in significant changes in the genetic and phenotypic parameters estimation, implying possible changes in the selection criteria, according to the environment. Thus, the identification of these interactions should contribute to the selection efficiency in cattle. To verify the presence of GxE, Falconer (1952) proposed that the same trait in different environments could be interpreted as different traits, since the genes that control it in a given environment may be different, at least in part, from those who control it in another environment. The aim of this study was to characterize and define homogeneous environments of production in composite beef cattle in Brazil, in relation to climatic and geographical variables and verify the presence of GxE for post-weaning gain (PWG), muscle score (MUS) and scrotal circumference (SC) in these environments.