ESTIMATION OF GROWTH CURVE PARAMETERS IN MEHRABAN SHEEP USING DIFFERENT NON-LINEAR MODELS

The aim of this study was to compare non-linear models to determine which model describes the growth pattern best for daily weight records of Mehraban sheep. The Nonlinear Negative exponential, Brody, Gompertz, Logistic, and von Bertalanffy models were applied. The data was collected between 2001 and 2010 from Mehraban breeding unit of the Agriculture Organization of Hamadan province in western Iran that were included 8299 daily weight records from 2206 animals from birth to 409 days of age. The NLIN procedure in SAS software was used to evaluate changes in body weight among different weighing age. The best model was determined by Adjusted Coefficient of Determination (R-adj(2)), Root Mean Square Error (RAISE) criteria, Akaike's information criteria (AIC) and Bayesian information criteria (BIC). For all models, R-adj(2) were mostly higher than 93%. Based on used criteria, the Brody model was selected as the best Model to explain the biological growth of Mehraban sheep. The results revealed that the Brody model can be practically useful for setting management strategies such as determining nutritional programs and the appropriate age for slaughter of Mehraban sheep.