Comparison of some non-linear mathematical models to describe the growth curve of Sistani calves

The purpose of this study was to fit different nonlinear models to describe growth curve and selection the best model to describe a growth curve forcalves of Sistani calves. Body weight records of 241 calves (118 males and 123 females) collected by the Sistani Dairy Cattle Research Station ofZahak from year 2010 to 2017 were used. Four nonlinear models (Gompertz, Logistic, Richards, and Weibull) were fitted to the body weight recordsand the best model was selected by the goodness-of-fit criteria (Mean square error, Bayesian information criterion, Akaike information criterion andcorrected coefficient of determination). According to goodness-of-fit criteria, Richards model was the most appropriate model to describe the growthcurve in male and female calves. The effect of sex on curve parameters was significant in many functions (P <0.05). Logistic and Richards models hadthe highest and the lowest initial weight parameter, respectively. Male calves reached to the inflection point in a higher age and weight compared tofemale calves. According to the results of this study, a proper model can be used to study the growth pattern of this breed in order to better nutritionalmanagement and selection for rapid growth with high accuracy.