Comparison of fitting performance of random regression animal and sire models for yield traits of Iranian Holstein dairy cattle

The main aim of this research was comparison of random regression animal and sire models for estimation of the genetic parameters for production traits of Iranian Holstein dairy cattle. For this purpose, were used the test day records 928513, 788577 and 653317 regarding milk, fat and protein yields, respectively, belonged to first of lactation of cows collected from 2003 to2010, by the animal breeding center of Iran.Number of Cows 108873, 96511 and 79501 and number of herd 1483, 1400 and 1227 for milk, fat and protein yields, respectively. The genetic parameters were estimated using restricted maximum likelihood algorithm by random regression model with legend repolynomials. For comparison of models, -2logL, Akaike’s information criterion, Bayesian information criterion and Residual variances criteria were used. Homogeneous residual variance was assumed throughout lactation. According to that used the records of all animals in the random regression animal model, therefore is high accuracy. Additive genetic variance and permanent environmental variance was higher in end lactation and beginning lactation, respectively. Estimates of heritability milk, fat and protein yields traits for both animal and siremodels were found to be lowest during early lactation. Estimates of heritability in the randomregression animal model for milk yield, fat yield and protein yield ranged from 0.05 to 0.25, 0.04 to 0.13 and 0.07 to 0.21 and in the random regression sire model 0.08 to 0.21, 0.05 to 0.12 and 0.5 to 0.23 in the during lactation were estimated, respectively. Phenotypic variance of the considered traits during lactation was not constant for both random regression animal and sire models, it was higher at the beginning and the end of lactation. Additive genetic correlation between adjacent test days was higher than between distant test days.The random regression animal model, purposed for estimation of the genetic parameters for production traitsof Iranian Holstein dairy cattle.