Methods of standardization of body weight for 205, 365 and 550 days of age were compared. It was used information of animals of the Nellore breed, raised in the Northeast Brazil, and controlled by the Brazilian Zebu Breeders Association (ABCZ). The following methods were compared: MET1 - used by ABCZ; MET2 - individual curves of linear regression for each animal; MET3 - individual curves of quadratic regression; MET4 - individual Brody curve; MET5 - used by the Program of Genetic Improvement of the Nellore breed (PMGRN); and MET6 -- individual Richards curves. There were differences among the means of the body weights calculated by the different methods. High correlations were verified among the methods. The variance and genetic parameters estimates were different among the methods. There were differences among methods used in Brazil with respect to their approach with the growth curve of the animals. In spite of the high genetic correlations and classification of the animals by their breeding values, the differences in this classification may influence the selection process and the expected response to it.
beef cattle; body weights; growth curves; non linear models; standardization methods
