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The aim was to evaluate the effect of genotype environment interaction (IGA) on the weights adjusted to 365 (P365) and 550 (P550) days of age of Guzerat cattle by Bayesian hierarchical models of reaction norm. The database used was provided by the Associação Brasileira de Criadores de Zebu (ABCZ) and contained 15169 and 11183 records for P365 and P550, respectively. An animal model (MA) and hierarchical models of reaction norm with homogenous and heterogeneous variances in one step (MHNRHO1P and MHNRHE1P, respectively) and two steps (MHNRHO2P and MHNRHE2P, respectively) were fitted to assess the existence and effect of IGA. The MHNRHO1P was the best fit model. Estimates of heritability in MA were 0,37 and 0,29 for P365 and P550, respectively. Heritability ranged from 0,21 to 0,71 for P365 and 0,06 to 0,93 for P550 on MHNRHO1P along the environmental gradient. Spearman correlations between the sires for P365 and P550 ranged from 0,26 to 0,99 and from -0,99 to 0,99, respectively, and genetic correlations ranged from 0,70 to 1,00 and 0,40 to 1,00 for P365 and P550, respectively. There is IGA in Guzerá cattle in Northeast Brazil for P365 and P550, and it is necessary to consider the possibility of including this effect in genetic evaluations. [ABSTRACT FROM AUTHOR]

To know the genetic and phenotypic progress of a population is important to evaluate the outcome of the adopted selection programmes and as guiding elements of future actions. The objective was to estimate genetic parameters, genetic and phenotypic trends of weights at 205 (W205) 365 (W365) 550 (W550) days of age, age at first calving (AFC), scrotal circumference (SC) and calving interval (CI) of 175.231 Nellore, born in the period 1967-2011 in the Northeast region of Brazil. The components of (co) variance and breeding values were obtained by restricted maximum likelihood methodology. Estimates of heritability coefficients for growth traits were of a low to moderate magnitude. Direct selection will provide greater genetic gains for W550. For reproductive traits, the heritability estimate was low for ACF and close to zero for CI. However, for the SC heritability was moderate, indicating its use as selection criteria. Direct genetic trends for W205, W365, W550 and ACF indicate small genetic gains over the years. Phenotypic progress shows that the features are improving with the years, mainly because of environmental improvements. [ABSTRACT FROM AUTHOR]