Detection of the Core Bacteria in Colostrum and Their Association with the Rectal Microbiota and with Milk Composition in Two Dairy Cow Farms.

As one of the pioneer bacterial sources of intestinal microbiota, the information of bacterial composition in colostrum might provide a reference for developing specific probiotics for newborn calves, especially calves fed with pasteurized milk. The present study aimed to detect the core bacteria at different taxonomic levels and the common beneficial ones in colostrum by analyzing the bacterial composition in 34 colostrum samples of healthy cows selected from two dairy farms. The results of the further analysis showed that the bacterial composition in the colostrum of the two dairy farms was different, but their four most dominant phyla were the same including Firmicutes , Bacteroidetes , Proteobacteria , and Actinobacteria. The microbiome of all colostrum samples shared ten core operational taxonomic units (OTUs), 21 core genera, and 34 core families, and most of them had no difference in relative abundance between the two farms. The ten core OTUs did not belong to the identified commensal bacteria and have not been detected by previous study. However, several core genera found in our study were also identified as core genus in a previous study. Some well-known beneficial and pathogenic bacteria including Lactobacillus plantarum , Bacillus subtilis , Acinetobacter lwoffii , and Streptococcus pneumoniae were present in the colostrum of healthy cows. However, none had a correlation with the number of somatic cell count (SCC), but the core genera Nubella and Brevundinimas and the core families Methylobacteriaceae and Caulobacteraceae positively correlated with the number of SCC. The genus Staphylococcus , Pseudomonas , and Chryseobacterium in colostrum had a positive correlation with each other, while the probiotics unidentified - Bacteroidales - S24 - 7 - group had a negative correlation with Pseudomonas and Chryseobacterium . In addition, more than 50% bacterial OTUs in colostrum were detected in the rectal content including some strictly anaerobic bacteria that are generally present in the intestine and rumen. However, of the top 30 commonly shared bacterial genera in the colostrum and rectal feces, no genus in colostrum was positively correlated with that same genus in rectal feces. In conclusion, the bacterial composition of colostrum microbiota is greatly influenced by external factors and individuals. There were several core OTUs, and some core genus and families in the colostrum samples. Colostrum from healthy cows contained both beneficial and pathogenic bacteria and shared many common bacteria with rectal content including some gastrointestinal anaerobes.