Growth curve in Anglo-Nubian goats raised in caatinga: nucleus herd and commercial herd

Abstract

The goal of this study was to evaluate the application of non-linear models in Anglo-Nubian goats on nucleus herd and commercial herd, both raised in the caatinga. After defining the best-adjusted model, the rate of absolute growth and the influence of environmental traits (breed, type of parturing and sex) on curve parameters were studied. The nucleus herd was composed of purebred animals (PO) raised under semi-intensive conditions. The commercial herd comprised animals raised under the traditional management system in caatinga. The non-linear models used were: Brody, Von Bertalanffy, Richards, Logistic and Gompertz. The Von Bertalanffy model presented the best adjustment. The animals from the commercial line are more precocious and present lower weights when adults than PO animals, semi-intensively raised. The type of breed and sex have significantly influenced (P<0.01) the asymptotic weight (A). The analyzed effects did not influence the growth rate (k) (P>0.05). The estimated correlation values between the parameters A and k were negative and equal to -0.76 and -0.61 for the nucleus herd and commercial herd, respectively, indicating that more precocious animals are less likely to reach higher weights when adults.