This paper had the objective of studying the influence of non genetic effects on the weaning weight of 105,465 calves of the Nellore cattle breed, born in eight different Brazilian regions, in the period of 1978 to 1994. The statistical analysis was accomplished using the least squares method, GLM procedure (SAS, 1996), with a model that included the fixed effects of sex, month and year of birth of the calf, region, farm within region and the covariable age of dam. All sources of variation included in the model were significant (P<0.0001). The importance of these non genetic effects on body weight of calf at 205 days of age indicates the need to consider them when estimating genetic parameters and breeding values for selection purpose.
animal production; beef cattle; diagnosis
