Weight records of 24.028 zebu animals from Guzerá, Nelore, and Polled Nelore breeds available from Brazilian Association of Zebu Breeders (ABCZ) database were used to estimate heritabilities of growth curve parameters. Non-linear Brody, Gompertz, Logistic, Mitscherlich, von Bertalanffy, Richards, and Double Logistic models including sex, farm, year of birth, month of birth, raising system, and interaction sex*raising system as fixed effects and sire and dam, as random effects were adjusted using weight-age records of animals which were born between 1960 and 2000, every three months, from birth to 24 months of age. Heritability estimates of growth curve parameters ranged from low to high values for all models and breeds. Genetic correlations between asymptotic weight and mature rate and asymptotic weight and growth rate were negative whereas those between mature rate and growth rate were positive. Phenotypic correlations between asymptotic weight and mature rate and asymptotic weight and growth rate were negative and those between mature rate and growth rate were positive. The variability observed in this study indicates the possibility of changing the growth curve by a breeding program, especially for the Nellore because more consistent records and results obtained for this breed.
Guzerá; Nelore; Nelore Mocho; maturity; variance components; zebu
