Hyperbolastic models as a new powerful tool to describe broiler growth kinetics.

The mathematical models for describing growth kinetics are important tools to examine biological parameters, such as BW at specific time, maximum growth response, and growth rates. Classical growth models such as Gompertz and Richards have been extensively used in broiler studies. To obtain a more intuitive understanding of growth, a class of flexible growth models containing 3 and 4 parameters were developed as hyperbolastic models. These models provide description of growth behaviors for continuous output in different fields, for instance cancer and stem cell growth. This study was conducted to find out if 3 flexible new hyperbolastic growth models, called type 1, 2, and 3 (H1, H2, and H3), may be used to illustrate relationship between live weight and age in broilers and also how effective such models would be compared with 2 classical growth models, namely Gompertz and Richards. A set of growth data over 70 d, obtained from 18 male broilers, was used to fit growth models. Goodness of fit of the models was determined using mean square error, R(2), and residual standard deviation. It was revealed that the 3 new models may be used to fit broiler growth data successfully and could be implanted in SAS PROC NLIN. Goodness of fit criteria refers better fit with H3, presumably due to its greater flexibility, followed by the Richards, Gompertz, H2, and H1. In conclusion, it seems that the H3 can be considered as a more useful tool for modeling broiler growth. However, it is reasonable to compare models for fit before selection of the more accurate one.