Growth curves in Dorper sheep crossed with the local Brazilian breeds, Morada Nova, Rabo Largo, and Santa Inês

The goal of the present work was to analyze the Brody, Von Bertalanffy, Richards, Logístic and Gompertz functions in order to describe the growth in crossbred sheep Dorper x Morada Nova (DMN), Dorper x Rabo Largo (DRL) and Dorper x Santa Inês (DSI). After defining the best adjusted model, the absolute growth rate was calculated and the influence of both environmental and genetic features on curve parameters was evaluated. The data were based on 156 F1 animals (36 DMN, 61 DRL and 59 DSI), weighed quarterly from birth up to 210 days of age. Both Gompertz and Logistic functions presented the best adjustment, being the latter slightly superior. The mature weight was statistically similar among the three genetic groups. However, the DSI group presented a faster growth during the pre-weaning period, with a remarkable fall from the inflection point on. The weight gain within such group was lower to those from DRL and DMN groups from 150 days of age on. Only the birth month has significantly influenced the asymptotic weight (A). The growth rate (k) was affected by birth month, type of parturition, sex, genetic group and parturition type vs. genetic group interaction. The estimated correlation between the parameters A and k were negative (-0.58 for DMN, -0.39 for DSI and -0.38 for DRL), indicating that more precocious animals are less likely to reach higher weights when adults.