The effect of the main factors related to milk production performance on microflora varies in Holstein raw milk

Abstract Background Milk microflora is closely associated with the physiology and pathology in the mammary gland, and plays an important role in offspring development. The objective of the study was to illustrate the variation of milk microflora accompanied by the main factors related to milk performance. Results Milk samples were collected from 285 cows in Ningxia, China, and then microflora was explored using 16S rRNA pyrosequencing. All samples were grouped with the season (summer and winter), cow status (healthy and subclinical mastitis), farms (6 commercial dairy farms), and parity (primiparity and multiparity). The bacterial diversity, community composition, and abundance were analyzed among different groups. Also, the milk microflora among samples from summer, winter, and colostrum was compared. The results showed that the bacterial diversity of the milk varied significantly between samples from summer and winter. Higher bacterial richness was observed from summer samples than from winter samples. The gut-related genera, Parabacteroides , Staphylococcus , Corynebacterium _1, Sphingomonas , and Lactobacillus , were prevalent in summer milk samples. Although Escherichia_Shigella , Pseudomonas , Streptococcus , Psychrobacter , Rhizobium , Bifidobacterium , and Clostridium_sensu_stricto _1 were common in winter samples. In addition, different farms exhibited differences in bacterial diversity. Subclinical mastitis increased alpha diversity and decreased the enrichment of KEGG pathways in summer. Moreover, significant differences of milk microflora were observed from summer, winter and colostrum samples. Conclusions The study revealed that the milk microflora varied companies with seasons, farms, health status, and parities. Also, milk from summer, winter, and colostrum showed their unique microflora characteristics.