Association between DRB3 gene Polymorphism and reproductive, immunity performance and heat tolerance in Holstein cow 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