COMPONENTES DE (CO)VARIÂNCIA PARA IDADE AO PRIMEIRO E AO SEGUNDO PARTOS DE FÊMEAS DA RAÇA NELORE CRIADAS NO SUL DO BRASIL

The objective of this study was to estimate the heritability, genetic correlation and estimated breedingvalues for age at first (AFC) and second calving (ASC) for Nellore females raised in SouthernBrazil. The (co)variance and estimated breeding values were obtained using Bayesian inference ina bivariate analysis, adopting an animal model. The average ages were 49.30 and 69.85 months,and the heritabilities were 0.25 and 0.26, respectively for AFC and ASC. The genetic correlationbetween AFC and ASC was 0.88. The correlation between the classifications of sires according totheir estimated breeding values was 0.93. The heritability estimates for AFC and ASC suggest thepossibility of obtaining genetic gain by selection. The correlation between these traits close to oneindicates that they are virtually controlled by the same genes, and the selection for one of them willpromote correlated advanced gain for the other. Keywords: Bayesian inference; beef cattle; genetic parameters; fertility.