Cattle and water buffalo belong to the same subfamily Bovinae and share chromosome banding and gene order homology. In this study, we used genome-wide Illumina BovineSNP50 BeadChip to analyze 91 DNA samples from three breeds of water buffalo (Nili-Ravi, Murrah and their crossbred with local GuangXi buffalos in China), to demonstrate the genetic divergence between cattle and water buffalo through a large single nucleotide polymorphism (SNP) transferability study at the whole genome level, and performed association analysis of functional traits in water buffalo as well. A total of 40,766 (75.5 %) bovine SNPs were found in the water buffalo genome, but 49,936 (92.5 %) were with only one allele, and finally 935 were identified to be polymorphic and useful for association analysis in water buffalo. Therefore, the genome sequences of water buffalo and cattle shared a high level of homology but the polymorphic status of the bovine SNPs varied between these two species. The different patterns of mutations between species may associate with their phenotypic divergence due to genome evolution. Among 935 bovine SNPs, we identified a total of 9 and 7 SNPs significantly associated to fertility and milk production traits in water buffalo, respectively. However, more works in larger sample size are needed in future to verify these candidate SNPs for water buffalo.

No abstract

The purpose of this study was to evaluate the effect of clinical mastitis between calving and next conception on reproductive performance in Chinese Holstein cows. Six hundred and three multiparous Holstein cows from a commercial dairy farm were divided into three groups respectively: cows with first clinical mastitis before first artificial insemination (AI) (MG1; n = 113), cows with first clinical mastitis between first AI and pregnancy diagnosis (MG2; n = 36) and cows without any clinical disease (CG; n = 454). Clinical cases of mastitis were identified at every milking by the trained milkers or the herd manager based on abnormal milk or signs of inflammation of the mammary gland. Number of days from calving to first AI and days from calving to conception, number of AI per conception, and the conception rate at first AI were evaluated in each group. The number of days to first AI was significantly greater for cows in MG1 than MG2 and CG (P < 0.01). The number of days to conception was similar for cows in MG1 and MG2 (P > 0.05), but they were all greater than cows in CG (P < 0.01). The number of services per conception was significantly greater for cows in MG1 and MG2 than CG (P < 0.01), and cows in MG1 had fewer number of services per conception as compared to MG2 (P < 0.05). Conception rate at first service was similar for cows in MG1 and MG2 (P > 0.05), however, conception rate for those groups were both lower than for CG (P < 0.01). In conclusion, clinical mastitis during early lactation markedly and negatively influenced reproductive performance of dairy cows. Therefore, reduction of clinical mastitis in early lactation should also improve reproductive performance of dairy cows. Further study is needed to better understand the mechanisms of how clinical mastitis affects reproductive performance in dairy cows which could lead to better strategies to avoid such negative effects.