Milk microbiome: evaluation study on the differences among cows with a different health status classified by leukocyte pattern

Milk is considered not only a source of nutrient for the offspring but also a font of immunoregulatory compounds capable to predispose the naïve intestinal immune system of the new-born to react to the external environment. In the present study we evaluated the composition of milk microbiome from cows classified according to milk total and differential somatic cell counts. A total of 34, 13 and 13 milk samples of healthy, at risk and subclinical or chronic cows, respectively, were collected during the same milking from a local dairy herd. Through Next Generation Sequencing (NGS) of bacterial 16S rRNA gene, the differences of taxa in terms of relative abundances (RA) and alpha and beta biodiversity were analysed. The RA of several genera were statistically significant in the three groups, such as Arcanobacterium (p=0.001), Rhodococccus (p<0.05) and Rubrobacter (p<0.05), while at species level the presence of Propionibacterium granulosum, Pseudomonas alcaligenes and Prosthecobacter debontii were found. Shannon and Evenness indices computed at the genus level were not significant, while beta biodiversity showed a clear clusterization between groups. The results highlighted that milk microbiome is associated to a different cellular response at udder level, although more specific studies are needed to assess the source of bacteria species identified in milk microbial population of healthy animals.