Variation of miRNA Content in Cow Raw Milk Depending on the Dairy Production System

Pasture-based milk presents several advantages over milk from intensive industrial farming in terms of human health, the environment, animal welfare, and social aspects. This highlights the need for reliable methods to differentiate milk according to its origin on the market. Here, we explored whether miRNA profiles could serve as a marker of milk production systems. We compared levels of previously described miRNAs in milk from four production systems (altogether 112 milk samples): grazing, zero grazing, grass silage or corn silage. Total RNA was extracted from the fat phase, and miRNAs levels were quantified by real-time quantitative PCR. The levels of the miRNAs bta-miR-155 and bta-miR-103 were higher in the grazing system than in corn silage farms. The levels of bta-miR-532, bta-miR-103 and bta-miR-7863 showed differences between different farm managements. The miRNAs bta-miR-155 and bta-miR-103 were predicted to participate in common functions related to fat metabolism and fatty acid elongation. All four differentially expressed miRNAs were predicted to participate in transport, cell differentiation, and metabolism. These results suggest that the dairy production system influences the levels of some miRNAs in milk fat, and that bta-miR-155 and bta-miR-103 may be potential biomarkers to identify milk from pasture-managed systems.