Growth curves in animal production

The properties of seven nonlinear models were discussed concerning its applications in the fitting of growth curves in animal production. The models used: Brody, Richards, Von Bertalanffy and two alternatives of Gompertz and Logistic models, were fitted by Gauss Newton method to weight-age data from eight animal species: freshwater prawn Macrobrachium rosenbergi, pepper frog, rabbit, poultry, sheep; goat, swine and cattle. Considering results of the fitted models such as convergence or not, coefficient of determination and biological interpretation of parameters, it was concluded that: a) the Logisticmethod y = A/(1 + e(-kt))(m) estimated body weight in all species, while the Von Bertalanffy model was not adequate only for freshwater prawn Macrobrachium rosenbergi; b) both Gompertz models were adequate for freshwater prawn Macrobrachium rosenbergi, pepper frog, poultry, swine and cattle; c) for each specie, at least two nonlinear of the seven models showed adequate to estimate the body weight of the animal species studied, because the coefficients of determination were above 92.0%.