Abstract:

【Objective】 The polymorphisms of κ–casein gene exon 4 and 5 and their correlation to milk performance traits in Chinese Holstein cattle were investigated for the purpose of providing molecular maker information to facilitate the breeding efficiency of high milk protein and milk fat. 【Method】 Sequencing, PCR-RFLP and CRS-PCR were applied to analyze the polymorphisms of six loci in κ–casein gene exon 4 and 5 in 544 Chinese Holstein cattle. 【Result】 Five SNPs in the exon five (A12907G, G12950A, C12989T, A13028G, T12980C) and one SNP in the exon four were found and A12907G, G12950A, C12989T, A13028G were closely linked. At locus A10996T, the cows with genotype TT and AT showed higher fat rate than those with genotypes AA (P＜0.05). At locus T12980C, the cows with genotype TC and CC was very significantly (P＜0.01) and significantly (P＜0.05) higher than TT genotype; with genotype TC and CC showed higher protein rate than those with genotypes TT (P＜0.05). At the remaining four loci, the cows with genotype DE showed higher fat rate than those with genotypes DD (P＜0.01). Seven haplotype and 16 haplotype combinations were found in 398 Chinese Holstein cattle,the cows with haplotype combinations H6H6 had the highest milk fat percentage and secondly was haplotype combinations H1H4. The cows with haplotype combinations H1H4 had the highest milk protein percentage and with haplotype combinations H5H6 had the lowest milk fat percentage and milk protein percentage. 【Conclusion】 Considering the distribution frequencies of haplotype combinations, κ-casein gene H1H4 is a favorable haplotype combinations to the milk fat percentage and milk protein percentage and can be chosen as the molecular markers of choosing high milk fat percentage and milk protein percentage.

Key words: Chinese Holstein')">Chinese Holstein, κ–casein gene, polymorphism, milk performance traits, haplotype