Mahdi Pourtahmasebian Ahrabi - Former MSc Student, Department of Animal Science, University of Tabriz, Tabriz, Iran

Objective: The main objective of this research was estimation of genetic parameters for five consecutive measurements of egg weights in Isfahan fowl using multi trait model and random regression models. Methods: The statistical models included generationhatch as a fixed effect, weeks of age as a covariate and additive genetic and individual permanent environmental effects as random effects. The date set included records of eggweight measured from 21 weeks to 84 weeks of age that collected during 15 generationsfrom 1986 to 2011. For acquiring of best accuracy of variance components anddetermining appropriate model, used heterogeneous residual variances with 5 classes and considering different orders of Legendre polynomial and accordingly eight different models were compared. Finally, the model with fourth order for additive genetic effect and third order for individual permanent environmental effect was selected as best model. Results: Results showed high genetic correlations of the 32 weeks of age with all other ages also its heritability indicated that it could be the optimum period for breeding

Egg weight ، Genetic parameters ، ، Isfahan flow ، Multitrait model ، ، Random regression ، model