برآورد پارامترهاي ژنتيكي صفات توليدي گاوهاي شيري هلشتاين در مناطق مختلف ايران

Estimation of genetic parameters of production traits of Holstein cows in different climate regions of Iran

In this study, records of 305-d and first lactation milk and fat yield of 102371 Holstein cows were used to estimate genetic parameters by DF-REML and univariate and bivariate animal model. These data were collected from 514 herds during 1991 to 2001 by Animal Breeding Center of Iran. Animals that with calving age out of 18-36 months and animals without any record were deleted. Sires from different countries were divided in 7 genetic groups and regions of Iran have been grouped in 5 climate regions based on extended De Martonne method. Heritability of milk and fat yield based on univariate model in different climate regions were ranged from 0.22 to 0.30 and 0.06 to 0.26, respectively. Mean of heritability based on bivariate model were ranged from 0.24 to 0.30 and 0.12 to 0.26, respectively. The difference of mean breeding values from the daughters of sires for each trait was significant (P<0.01). Given positive correlation between these traits, in most regions, the highest and lowest average breeding value were belonged to daughters of Newzland and Iranian sires, respectively.