Comparison of nonlinear models for estimating growth parameters and growth curve of Raeini Goat

In this study, it was aimed at estimating of the growth curve in Raeini Cashmere goats. For drawing growth curve, records of weight-age data of 6765 female and male goats were individually fitted to Brody, Von Bertalanffy, Verhulst, Logistic and Gompertz growth models. The growth models were compared using the coefficient of determination (R2), residual mean square error (MSE), Akaike’s information criterion (AIC) and a number of interations. Among all nonlinear models, the highest R2 and the smallest AIC, MSE values and number of interations were calculated by Brody function for both sexes. Moreover, males have higher A (weight at maturity) and B parameters than females and have a lower K parameter (rate of maturity) than females. As the Brody growth curve, female adult live weight was lower than males, because sex factor significantly influences on live weight. The range of inflection point 4.80 and 7.89 for females, 5.86 and 9.55 for males, respectively. The lowest of an inflection point in both sexes estimated for Von Bertalanffy model, and highest inflection point estimated for logistic in both sexes. The lowest and highest of inflection age in both sexes estimated for Von Bertalanffy and Verhulst models, respectively. In conclusion according to the results of this study, the nonlinear Brody growth model seems to be the most appropriate to adjust the growth curve of the Raeini Cashmere goats.