Abstract:

【Objective】 Through the method of genetic breeding to improve the mastitis resistance and reduce its incidence, and find the candidate genes associated with mastitis. 【Method】 The single nucleotide polymorphisms (SNPs) within the coding regions of IL8RA and IL8RB genes in Holstein cattle were investigated by nested-PCR, DNA sequencing and CRS-PCR. The PHASE and SHEsis software was used as matching chain disequilibrium and haplotype analysis, respectively. 【Result】 Eight SNPs not linking were found, in which five SNPs were 980(G/A), 995(G/A), 1008(C/T) of IL8RA and 938(C/T), 959(C/T) of IL8RB were reported for the first time. Haplotype analysis of IL8RA and IL8RB genes showed that fifteen haplotypes frequencies more than 0.01. The assocaition analysis of SNPs with the Chinese Holstein cattle somatic cell score (SCS) and milk yield showed that: 735(C/G), 816(C/A), and 819(A/G) loci of IL8RA gene had related with the SCS and milk yield, the C, C, G alleles of 735(C/G), 816(C/A), and 819(A/G) sites in IL8RA and T allele of 938(C/T), 959(C/T) locus in IL8RB gene were excellent allele with lower SCS, higher milk yield. In addition, the SCS of CCGAAC haplotype homozygous in IL8RA gene individuals was significantly lower than that CAGGGT and GCAGGC haplotype homozygous individuals (P＜0.01), while the 305 d milk yield was significantly higher than the other two haplotype. The SCS of haplotype CT homozygous individuals in IL8RB gene was significantly lower than CC, TC and TT haplotype individuals, while the 305 d milk yield of haplotype CT homozygous individuals was significantly higher than the other three haplotype individuals. 【Conclusion】 The haplotypes CCGAAC and CT of IL8RA and IL8RB gene are excellent haplotypes in the SCS and milk production quantity and can be used as selection markers of remastitis.

Key words: Chinese Holstein cattle, interleukin-8 receptor gene, haplotype, excellent alleles, mastitis resistance