Effect of the genotype and environment interaction on body weight traits in Nelore cattle (Bos indicus).

The aim of this study was to evaluate the genotype-environment interaction and its impact on the genetic evaluation of sires for body weight traits in Nellore cattle. Records of standardized weights at 120 (W120), 210 (W210), 365 (W365), and 450 (W450) days of age were used for 28,570 Nelore cattle, the progeny of 179 sires and 17,998 dams from herds in the states of Mato Grosso, Mato Grosso do Sul, and Goiás. The months of birth of animals were grouped into seasons that corresponded to the months with the lowest and highest rainfall. The variance components and prediction of breeding values of the animals were estimated. As a result, the posterior means of additive genetic variance components for W120 and W210 were higher in Mato Grosso compared to Mato Grosso do Sul and Goiás and which single-trait model. Posterior means of direct heritability's for W120 and W210 were higher in Mato Grosso. Regarding yearly (W365) and yearling (W450) weights, the posterior means of the additive genetic variance components for Goiás were higher than those for Mato Grosso and Mato Grosso do Sul and for the single-trait model. The state of Mato Grosso, in turn, was the one that presented the posterior mean of the higher residual variance component for W450. Posterior regression coefficients for W120 and W210 indicated that the breeding values of the sires were underestimated by the single-trait model in the state of Mato Grosso. Spearman's and additive genetic correlation coefficient values indicated changes between the ranking of sires for body weights, especially between Mato Grosso (MT) and Mato Grosso do Sul (MS). It is concluded that there is a presence of GxE on the selection criteria for the weight development of Nelore cattle in the Midwest Region of Brazil.