Evaluation of non-linear equations to model different animal growths with mono and bisigmoid profiles.

Experimental data of different animals (e.g. cocks, pigs, cats, dogs, cattles, etc.) from recent bibliography were selected to evaluate the capability of five classical sigmoidal equations (i.e. Bertalanffy, Weibull, logistic, Gompertz, and modified Hill) to model growth. These functions were used in different reparameterized forms in order to define all growth phases and to characterize significant kinetic parameters. The results indicated that logistic and Weibull equations were the best options to simulate the data with mono-sigmoid profiles. A subsequent formulation of logistic and Gompertz equations was constructed to describe accurately the biphasic trends for cock and foal growths.