author(s)
Mohamed TR, AL-Anbari NN and Al-Waith HK

abstract
This investigated was conducted at Al-Salam station for Dairy cattle / private sector, from 1-11-2016 to 1-11-2017, to determine the association between DRB3 gene’s genotypes with some reproductive traits, immunity and heat tolerance coefficient in Holstein cows. The results DRB3 gene analysis showed a highly significant Different (P<0.01) between genotypes of DRB3 gene’s genotypes A,B & C, the percentage were 46.00, 42.00 and 12.00% respectively. The results of the current study showed that services per conception and days open was significantly affected (P<0.05) by different genotypes of the DRB3 gene for the cows with A genotype. There was also a significant difference (P<0.05) between the genotypes of DRB3 gene for IgG concentration in calves blood. The concentration of IgG in this study 42.9± 2.39 & 42.75 ± 1.98 g/L. blood which belong to cows with A & B genotypes respectively and it was higher than claves which belong to cows with C genotype (38.08 ± 1.62 g / L. blood). For the heat tolerance coefficient it was found that there was a highly significant (P<0.01) difference between the genotypes of the DRB3 gene in this trait and for the cows with C genotype 105.65 ± 0.56 in the second month of the lactation season, and for the cows with A & B genotype (102.76 ± 0.63 and 103.05 ± 0.43 respectively), while there was no effect of DRB3 gene genotypes of the heat tolerance coefficient during the first and third months of the lactation season.