Association of promoter region of TLR4 gene with somatic cell count in a Holstein dairy herd in Isfahan province

Mastitis is one of the most prevalent diseases of dairy cattle. In order to create genetic resistance to the disease, it is essential to identify resistant genes to mastitis. Toll-like receptors are the suitable candidate genes for enhancing genetic resistance to mastitis in Holstein cows. In this research, polymorphism of TLR4 gene’s promoter and its association with somatic cell count in a herd of Holstein cows in Isfahan was studied. For this purpose, DNA was extracted from 100 blood sample of Holstein cows. Two primers were used for amplifying the promoter of TLR4’s gene. These primers amplified 274bp fragments using polymerase chain reaction (PCR) method. The amplified fragments showed A and B genotypes with 0.74 and 0.26 frequency respectively. The results of this study showed that these two different genotypes have significant effect on somatic cell count in the studied herd (P<0/01). With respect to low heritability of somatic cell count (0.093) and deficiency of direct selection for improving of this characteristic, selection on the basis of TLR4 genotypes can efficiently used for increasing genetic resistance to mastitis.