Description of Growth Curve in Male and Female Lambs of Baluchi Breed by Application of Nonlinear Growth Models

The purpose of this study was to describe growth curve in Baluchi sheep by application of nonlinear growth models. The weight records of 1228 and 676 Baluchi male and female lambs for birth weight, one-month, two-month, three-month, four-month, six-month, nine-month and one year of age were studied. These data had been collected by Baluchi Sheep Breeding Center in Mashhad (Abbas Abad) during 2004 to 2009. Brody, Von Bertalanffy, Gompertz and Logistic nonlinear models were fitted to describe the growth curve. The most suitable model was determined by R2, Root MSE, as well as mean absolute error (MAE). For data analysis, NLIN procedures were used. The results of this research for male lambs showed that Brody model with R2 (90.42%), Root MSE (8.35) and mean difference between expected and observed value (MAE) (5.65) was the best model compared with others, this value for proper model (Von Bertalanffy) in female lamb were 96.85% (R2), 4.54 (Root MSE) and 3.16 (mean difference between expected and observed value). The correlation between A and K parameters for Von Bertalanffy, Brody, Gompertz and Logistic were -0.36, -0.54, -0.3 and -0.21, respectively.