Inflammation-related Gene Polymorphism And Its Correlation Analysis With Dairy Cow Mastitis

Bovine mastitis is a common disease in modern dairy farm.The occurrence of mastitis will reduce the economic benefits by affecting the milk production and milk quality of dairy cows.The use of therapeutic drugs will not only affect the quality of milk,but also promote the development of drug resistance.The deletion of disease resistance genes is of great significance for the early diagnosis and prevention of mastitis,the reduction of morbidity,the reduction of feeding costs and the improvement of production performance.Therefore,this study identified single nucleotide polymorphisms?SNPs?of genes related to inflammatory response in Chinese holstein cows and verified the correlation between SNPs and milk lactation performance and the occurrence of mastitis.The identification of effective molecular marker sites for mastitis resistance at the gene level will lay a foundation for the exploration of molecular regulation mechanism of resistance factors,and also provide a basis for early diagnosis,prevention and treatment of bovine mastitis.In this experiment,blood samples of 320 cows from a dairy farm were used as research materials.DNA was extracted from them,and multiple inflammation-related genes were verified by direct sequencing.SNPs of Toll-like receptor 1?TLR1?,Cbl proto-oncogene B?CBLB?,and chemokine ligand 2?CXCL2?were selected for detection.Genotyping identification of SNP loci by PCR-RFLP method.Calculating the genetic parameters of the relevant SNP loci and using SPSS 21.0 software to analyze the correlation between the SNP loci and the production performance and the occurrence of bovine mastitis.The results showed that a total of 4 SNP sites were found in the TLR1 gene:C¹⁴²⁴A,A¹⁴⁷⁵C,G¹⁴⁹⁶A and G¹⁵⁵⁰A.Comparing the sequencing results with the discovery of restriction enzymes,it was found that the mutation frequencies of C¹⁴²⁴A,A¹⁴⁷⁵C,and G¹⁵⁵⁰A were not suitable for this test.Therefore,the correlation analysis was performed with the G¹⁴⁹⁶A locus,and it was found that the locus had a very significant correlation with milk fat rate,SCC and the incidence of clinical mastitis?P?0.01?.In the CBLB gene,one SNP site was found:G²²²⁴⁰⁶T.The results of the correlation analysis showed that the SCC of the GG type was significantly higher than that of the TT type?P?0.01?,and there was no significant difference between the GT type,GG type and TT type?P>0.05?.In the CXCL2 gene,a total of 4 SNP sites were found:G²⁶⁸A,C²⁷⁹T,C³¹⁶G and G⁴⁶⁸A.Comparing the sequencing results with the discovery of restriction enzymes,it was found that the mutation frequencies of G²⁶⁸A,C³¹⁶G and G⁴⁶⁸A were not suitable for this test.Therefore,the correlation analysis was conducted at the C²⁷⁹T site,and it was found that there was no significant correlation between this site and CC type and TT type?P>0.05?,the SCC of CC type and TT type is significantly higher than that of CT type?P?0.01?.In summary,after analyzing the SNPs of TLR1,CBLB and CXCL2 and their correlation with DHI production performance,it was initially found that the G1496A locus of the TLR1 gene,the G²²²⁴⁰⁶T locus of the CBLB gene and the C²⁷⁹T locus of the CXCL2 gene were significantly correlated with milk fat rate,SCC and incidence of bovine mastitis,which could be used as candidate marker factors for molecular assisted selection of bovine mastitis resistance.