Mathematical models describing growth kinetics are important tools to predict biological phenomena such as BW at a specific age, a maximum growth response and/or growth rates. Classical models such as Gompertz and Richards have been extensively used to describe broiler studies. Recently, for accurate prediction or describtion of growth behavior in biological system, a group of flexible growth models known as hyperbolastic with 3 or 4 parameters are introduced. These models may predict variety of growth behaviors for continuous output as occurs in cancer and stem cell growth studies. In the present study, three new flexible hyperbolastic growth models, called H1, H2 and H3 were evaluated to determine their strength in describing the relationship of BW and age of broilers or compatibility with two classical growth models of Gompertz and Richards. A growth data set of 217 male broiler chickens raised for 170 days were used to test and compare the fitness of the growth models. Goodness of fit for the models were determined by Mean Square Error (MSE), R2, Residual Standard Deviation (RSD), Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). Based on our overall calculated goodness of fit criteria, it is revealed that the H3 model provides the most promising fit and it was reduced when the H2, Richards, Gompertz and H1 models were used, respectively. The more precise fitness observed with the H3 model might be due to its more flexibility. The hyperbolastic growth models in particular the H3 model is considered to be a more accurate tool for predicting broiler growth curve. However, it suggested to examine the fitness of different models to hire the best fit.

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