Curvas de crescimento de fêmeas da raça nelore e seus cruzamentos

Abstract

Selection for growth characteristics can be done after fitting growth functions for all breeding animals. However, in the female population the growth curve is influenced by gestation and subsequent lactations. In this work methods are described to select a function that fits a growth curve of bovine females considering the varying effects of body weight due to gestation and lactation. Data from the Paraná Agronomic Institute (IAPAR) were used consisting of 15.271 weight observations of 103 females distributed as 43 Nelore, 10 F1 Guzerá x Nelore, 29 F1 Red Angus x Nelore, 5 F1 Marchigiana x Nelore and 16 F1 Simental x Nelore. The function adjustment of Brody, Gompertz, Logística, Von Bertalanffy and Michaelis-Menten reparametrized MMr were compared to the effects of weight gain as a function of age, adding to all functions the weight gain during gestation and the weight loss in the lactation of Nelore and crossbreed females. It was observed an Adjusted Coefficient of Multiple Determination varying from 0.7552 to 0.9267. Lower Residue Mean Square and Absolute Mean Deviation were observed for the MMr function. The MMr function must be adjusted in order to describe the growth curve as a function of the female age.