Heritability estimates for age at first calving in Nelore cattle

Genetic parameters were estimated for, approximately, 6,000 records of age at first calving (IPP) in Nelore cattle using three different definitions for contemporary group. The univariate analysis considered as fixed effect: contemporary group (GC) and linear and quadratic effects of dam age (IDV). First contemporary group (GC1) was defined by farm, year and season at birth, management group at birth, weaning and yearling and mating type. Second contemporary group (GC2) included the same variables of GC1 and year and season at calving. Third contemporary group (GO) was determined by year and season of birth, farm, year and season of calving and mating type. The heritability estimates for IPP were 0.16 +/- 0.03, 0.09 +/- 0.03 e 0.11 +/- 0.02, respectively, to GC1, GC2 and GC3.