Extended Abstract
Introduction and Objective: In the dairy industry, it is important to identify the genotypes resistant to mastitis while select high-yielding dairy cows. Bovine β-difensin gene polymorphism can be used as a molecular marker in the selection of mastitis-resistant dairy cows. The aim of this study was to investigate the relationship between point mutation of β4-difensin gene and the occurrence of clinical mastitis in the dairy cows using RFLP-PCR method and identification of superior genotype of dairy cows β-difensin gene for mastitis resistance.
Material and Methods: blood sample (with EDTA anticoagulant) was taken from total 73 cows (32 with a history of mastitis and 41 with no history of mastitis) in an industrial dairy farm. After DNA extraction amplification of the region of bovine β-difensin gene (393 bp) was performed. PCR products were digested by endonuclease (NlaIII (Hin1II)) for rapid detection of polymorphism in the 2239 region of the β-difensin gene (C to T conversion). Statistical analysis was performed by Chi-square test.
Results: Allele frequencies were 0.68 and 0.32 for C and T, respectively. Statistical analysis was performed by Chi-square test. The results of this study indicate the association between number of mastitis and polymorphism in the β-difensin gene. In other words, the incidence of mastitis was  numerically lower in cows with T allele than in cows without it (p=0.07).
Conclusion: It can be concluded that the bovine β-difensin gene can also be used as a molecular marker in the selection of dairy cows to reduce the incidence of mastitis.