This study was conducted in Al-Salam station for Dairy cattle/private sector, for the period from 1-11-2016 to 1-11-2017, to determine the association between BTN1A1 gene polymorphism and reproductive efficiency indicator and heat tolerance in 50 Holstein cows. The results of BTN1A1 gene analysis showed a highly significant Different (P<0.01) between genotypes of BTN1A1 gene’s genotypes AA, AB the percentage were 72.00, 28.00 % respectively. Results showed that services per conception and days open was significantly (P<0.05) affected by polymorphism of BTN1A1 gene and for cows with AA genotype, there was also a significant difference (P<0.05) between the genotypes of BTN1A1 gene for IgG concentration in calves blood who belong to mother’s with AA genotypes compared with AB genotype, for the heat coefficient tolerance trait the results showed a significant different (P<0.05) with BTN1A1 polymorphism and for cows with AB genotype in third month of lactation, while there are no significant differences in other months of lactation with different genotypes of BTN1A1 gene. It was possible to conclude from this study the possibility of BTN1A1 gen’s polymorphism in the development of genetic improvement strategies and breeding programs that achieved the best productive performance in dairy cows.
