Abstract:

The purpose of this study was to identify significant SNP loci or combinations relevant to cow udder health, so as to improve udder health in dairy cattle and promote the healthy development of the dairy industry in "the Belt and Road" countries. In this study, genomic DNA was collected from the tail vein blood of 1 097 Chinese Holstein and 161 Pakistani Holstein, and the tail root hair follicles of 116 Achai cattle and 104 Red Sindhi. Chinese Cow's SNPs Chip-I (CCSC-I) was used to obtain the genotype. In conjunction with udder health indicators from corresponding DHI reports—somatic cell count (SCC) and somatic cell score (SCS), significant SNPs or combinations were identified through single SNP and pairwise SNP association analysis. The unit point association analysis showed that SNP3, 6, 8, 11, 19, and 20 were significant loci in the Chinese Holstein(P < 0.05), with SNP3 and 11 identified as significant loci in the Pakistani dairy cattle population(P < 0.05). In pairwise SNP association analysis, stable combinations of SNP11-SNP15 were retained for the Chinese Holstein using large samples (farms in Beijing, Zhejiang, and Hebei provinces) and samples from Hebei province specifically, with the AA genotype predominating for SNP19 and SNP20. Significant combinations of SNP11-SNP2, 4, 8, 9, 12, 16, 19 were identified for Pakistani Holstein(P < 0.01), and significant combinations like SNP3-SNP11, 15 were identified for the Pakistani indigenous Achai(P < 0.01). The results of this study show that Chinese Cow's SNPs Chip-I exhibits wide applicability. SNP11, 15, 19, 20 and other loci have important effects on cow udder health. In Holstein populations, CD4, TRAPPC9, and PTK2 showed potential resistance to mastitis. In the Pakistani indigenous dairy cattle populations, CD4, DGAT1, and TRAPPC9 showed significant resistance characteristics. These findings provide a strong scientific basis for future accurate breeding.

Key words: Chinese Holstein, Pakistani Holstein, Pakistani indigenous dairy cattle, mastitis, SNP