Growth rate curves of Indubrasil cattle raised at Sergipe State

Abstract

The objective of this study was to analyze nonlinear models to describe growth of Indubrazil cattle raised in Sergipe State. After defining the best adjusted model, it was evaluated the influence of environmental effects (sex, farm, month and year of birth) over mature weight (A) and maturation rate (k). Data from 1,201 animals weighed in nearly 90-day intervals from birth up to two years of age were used, based on records from the Brazilian Association of Zebu Breeders (ABCZ). The models utilized were Brody, Von Bertalanffy, Richards, Logistic and Gompertz. The Logistic model presented best adjustment followed by Gompertz and Von Bertalanffy models. The parameters A (weight at maturity) and k (maturation rate), obtained by the Logistic model were 427.87 and 0.0052, respectively. An accentuated decrease in the absolute growth rate was observed after weaning and nutritional strategies should be performed to avoid the low weight gain at this stage. Environmental factors affected significantly the parameters A and k. The correlation estimated between the parameter A and k was negative (-0.62), indicating that fast-growing young animals are less likely to reach higher weights when adults.