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This study was conducted to compare of random regression (RR) animal and sire  models for estimation of the genetic parameters for production traits of  Iranian Holstein dairy cows. For this purpose, the test day records were used  belonged to first three lactations of cows and for, milk, fat and protein  yields traits where, collected from 2003 to 2010, by the national breeding  center of Iran. The genetic parameters were estimated using restricted  maximum likelihood algorithm. To compare the model, different criterion  -2logL value, AIC, BIC and RV were used for considered traits. Residual  variances were considered homogeneous over the lactation period. Obtained  results showed that additive genetic variance was highest in the beginning  and end lactation and permanent environmental variance was highest in  beginning of lactation than other lactation period. Heritabilities estimate  for milk, fat and protein yields by RR animal and sire models were found to  be lowest during early lactation (0.05, 0.04 and 0.07; 0.05, 0.19 and 0.13;  0.14, 0.19 and 0.15, for milk, fat and protein yields and in first, second  and third lactation respectively). However, estimated heritabilities during  lactation did not vary among different order Legendre polynomials, and also  between RR animal and sire models. The variation in genetic correlations  estimate in the RR animal and sire models was larger in the first lactation  than in the second and third lactations. Thus, based on the results obtained,  it can be inferred that the RR animal model is better for modeling yield  traits in Iranian Holsteins.

biotechnology in animal husbandry/biotechnology in animal husbandry

Estimation of genetic parameters and comparison of random regression animal and sire models of production traits in the first three lactations of Iranian Holsteins