Analysis of Fitting Growth Models in Medium Growing Chicken Raised Indoor System

Medium-growing broilers that were reared under mixed-sex condition in confined system were used in this study. A profile analysis was made for the time-dependent live weight values of female and male broilers, and it was determined that the profiles were not parallel (P<0.01). The growth data measured until the 63rd day, the slaughter age of broilers, were analyzed with three growth curve models. With this purpose, a comparison was made regarding the goodness of fit of three-parameter Bertalanffy, Gompertz and Logistic nonlinear regression models that were used most for the poultry. In order to determine goodness of fit for the growth data of female and male broilers, the values of coefficient of determination (R 2 ), adjusted coefficient of determination (adj. R 2 ) and mean square error (MSE) were used. Values of R 2 and adj. R 2 were found to be quite high for each of the three models; however, it was determined that the fittest model for both female and male broilers according to MSE was the Gompertz growth curve. The value of asymptotic weight (β0), integration constant (β1) and maturity rate (β2) parameters derived from Gompertz model were 3657 g, 4.14 and 0.031 for female and 4,362, 4.37 and 0.031 for male, respectively. Age at inflection point (IPA) and weight of inflection point (IPW) were 46 days of age and 1345 g for female and 48 days of age and 1605 g for male, respectively.