Identification of Genetic Variation in two Candidate Genes of TLR2 and TNFα and its Association with Mastitis in Holstain Cattle

Mastitis is one of the most common diseases in dairy cattle, which has imposed therapy heavy costs to farmers through significant reduction in total milk production. Identification of nucleotide polymorphism of two candidate immunity response genes and its effects on SCS as a mastitis incidence indicator was carried out in this research. The genes were exons 1 and 2 of TLR2 and 3 and 4 of TNFα. For this purpose, a hundred Holstein lactating cows were selected based on their breeding values for milk production, fat and somatic cell scores. Then cows based on their residual values for somatic cell scores were divided into two resistant and susceptible groups and 5 ml blood samples were collected from each animal. Selective genotyping of two target groups of susceptible and resistant animals to mastitis was done using PCR-RFLP approach. The association between genetic polymorphisms with corrected records of somatic cell scores (residual values for somatic cell score) were analyzed using the Generalized Linear Model (GLM) procedure of SAS statistical package (version 9.2) followed by means comparison with Tukey-Kramer test. There was a significant direct relationship between TLR2 and TNFα gene polymorphisms and somatic cell score residual values (P