The Relationship Between BoLA Gene Polymorphism And Mastitis Of Dairy Cows

Mastitis is a major cause of economic loss to the dairy cows and dairy industry, while Major Host-compatibility Complex (MHC) is a chromosomal region, consisting of a group of closely linked loci which are highly polymorphism, and plays a very important role in the immune system. It has been certificated that MHC is associated with animal's resistance or susceptibility to various diseases. In this research,the molecular genetic polymorphisms were investigated for MHC-DRA locus, DQA locus, DQB locus and DRB3 locus by PCR-SSCP method in Chinese Holstein, Chinese Simmental, and Sanhe Cattle. Furthermore, the relationship between polymorphisms and mastitis, and the factors influencing the mastitis were also analyzed. The result shows as follows: 1. Three alleles of the BoLA-DRA* exon2 have been discovered, with three alleles in Chinese Holstein, three ones in Chinese Simmental and three ones in Sanhe Cattle. In addition, eleven alleles of BoLA-DQA* exon2 have been discovered, with seven ones in Chinese Holstein, seven ones in Chinese Simmental and eleven ones in Sanhe Cattle. Furthermore, thirteen alleles of BoLA-DQB* exon2 have been discovered too, with eight ones in Chinese Holstein, twelve ones in Chinese Simmental and twelve ones in Sanhe Cattle. Moreover, ten alleles of BoLA-DRB3* exon2 have been discovered, with eight ones in Chinese Holstein, nine ones in Chinese Simmental and eight ones in Sanhe cattle. 2. Some genes or genotypes are probably positive correlated with the susceptibility of mastitis in Chinese Simmental and Sanhe Cattle, which are as follows: the CC genotype of the DRA*exon2, the B gene of the DQA*exon2, the BB and FF genotype of the DQA*exon2, the D gene of the DQB* exon2, the DD genotype of the DQB*exon2, the E gene of the DRB3* exon2 and the EE genotype of the DRB3*exon2. However, some other genes or genotypes are probably positive correlated with the resistance to mastitis in Chinese Simmental and Sanhe Cattle, which are as follows: the BC genotype of the DRA* exon2, the A gene and G gene of DQA* exon2, the AA genotype of the DQA*exon2, the A gene of DQB* exon2, the AA genotype of the DQB*exon2, the B gene of DRB3*exon2 and the BB genotype of the DRB3 * exon2. In contrast, the susceptible or resistant gene and genotype of mastitis was not observed in Chinese Holstein Cattle in this study. 3. Two haplotypes of DQA-B/DRB3-C and DQA-G/DRB3-F are positive correlated with the susceptibility of mastitis in Chinese Holstein, while the haplotype of DQB-F/DRB3-E is positive correlated with the resistance of mastitis in Chinese Holstein. In addition, the haplotype of DRA-C/DQA-A is positive correlated with the susceptibility of mastitis in Chinese Simmental and Sanhe Cattle, while the haplotypes of DRA-B/DQA/E, DRA-C/DQA/E, DRA-B/DQA/E, DRA-C/DQA/E, DRA-B/DQB-A, DRA-B/DQB-M, DQA-A/DQB-J, DQA-E/DQB-M, DQA-F/DQB-C, DQA-J/DQB-B, DQA-K/DQB-D, DQA-A/DRB3-B, DQA-K/DRB3-F, DQB-B/ DRB03-H and DQB-M/DRB3-B are positive correlated with the resistance of mastitis in Chinese Simmental and Sanhe Cattle. 4. Chinese Holstein is easier to suffer from mastitis than that of Chinese Simmental and Sanhe Cattle. In addition, along with the growth of the age, the rate of the mastitis increases in dairy cattle. Moreover, in the rain season, it is much easier for the dairy cattle to suffer from mastitis. What's more, along with the extension of the lactation month and the gravid times, there has been a trend of increasing the rate of the mastitis. 5. In the BoLA-DRA, DQA, DQB and DRB3 locus, the genotype of BoLA-DRB3 has the largest influence on the SCSLAW which is a marker index of mastitis in dairy cattle.