Idade da vaca e mês de nascimento sobre o peso ao desmame de bezerros nelore nas diferentes regiões brasileiras

Abstract

The aim of this study was to verify the existence of interaction between age of dam effect and month of birth effect on weaning weight with the studied regions. Records of 333,259 Nelore animals from Brazilian Association of Zebu Breeds (ABCZ) were analysed. The analysis was carried out using the least squares method. Effects of year of birth, sex, farm and interactions between month of birth and region, and age of dam and region were considered. All effects included in the model affected significantly weaning weight. The Northwest, Center-west, Southeast and South regions were compared using Conditional Residual Model to verify differences on month of birth effect and age of dam effect. For all regions, month of birth effect and age of dam effect on weaning weight were statistically significant (P<0,01). The interaction between age of dam and region, and month of birth and region are an important source of variation on weaning weight. To increase the income and to facilitate the handling, breeding seasons should be established for each region.