Study of bovine milk microbiota biodiversity in autoctonous italian breeds

In order to valorize the autoctonous cows milk, a better knowledge of its quality and features is requested. In the last few years a large interest on the milk microbiota composition has raised due to the impact of the microorganisms could have on the health status of the animals, on the public health and on the quality of the dairy products. Preliminary data on mammary microbiota of the ruminant species (cow, sheep and buffalo) showed that the row milk includes a complex community of microbes affected by both endogenous and esogenous factors. The present study aims to better understand the differences of the molecular mechanisms of the microbiota interaction in the Rendena’s milk compared to Holstein breed. Microbial composition of the milk from 3 Rendena cows was compared to that from 3 Holstein cows from the same farm with the same management. Quarter samples were collected from each cow at different time points: dry off (T1), at calving (T2), 7-10 days after calving (T3) and 30 days after calving (T4). We analyzed somatic cell count (SCC) and bacteriological culture for each quarter. For the microbiome analysis, the bacterial DNA was extracted from each quarter using a protocol previously described (Cremonesi et al., 2005) with some modifications and the 16S rRNA gene (V3-V4 region) was analyzed by Miseq (Illumina). Bacteriological analysis showed the absence of contagious bacteria such as Staphylococcus. aureus and Streptococcus. agalactiae in both breeds. The predominant Rendena’s phylum was Firmicutes (94.3%). In Holstein the milk microbiota was more complex with Firmicutes (62.6%), Proteobacteria (19.2%), Bacteriodetes (7.5%) and Actinobacteria (6.8%). The analysis of the genera showed that in Rendena cows the main microorganisms were Streptococcus (70.7%), Lactobacillus (10.4%) and Pediococcus (5.8%), whereas in the Holstein cows were Streptococci (27.1%), Staphylococci (5.5%) and Lactobacilli (4.5%). Regarding the species of the Streptococcus genus we demontrated a significant difference between the two breeds. Indeed, in the Rendena cows the 51,6% of the present Streptococci were Streptococcus thermophilus, that in the Holstein cows represent only 1.72% of the observed Steptococci. Streptococcus thermophilus is a lactic bacterium very usefull in the dairy products (fermented milks, yogourt, different cheeses). The strong presence of Streptococcus thermophilus in the Rendena milk makes it more suitable for the dairy industry. The different microbial composition of the milk from the two breeds could also have an impact on the immune response and the infections of the udder that could help to explain the high resistance to mastitis of the autoctonous Italian cow breeds. In order to better clarify this hypothesis gene expression and proteomic analysis are in progress.