Different Diets Change Milk Extracellular Vesicle-Protein Profile in Lactating Cows

We previously demonstrated that the partial replacement of forage with non-forage fiber sources (NFFS) in dairy cow diets could decrease the ruminal ratio of acetate to propionate, leading to changes in circulatory and milk extracellular vesicle (EV)-miRNAs expression. This study further explored the effects of the NFFS diets on milk EV proteins, which were proposed as food bio-active ingredients in recent research. We replaced 8.97% alfalfa hay and 2.51% corn silage with 5.72% whole cotton seed and 4.73% soybean hull in the cow diet, reducing the forage neutral detergent fiber from 20.92% to 15.67%. In total 488 proteins were identified by proteome, and 65 proteins were differentially expressed in response to the NFFS diets, the functions of which were mainly enriched in immune-related pathways, including complement and coagulation cascades, phagosome, Staphylococcus aureus infection, and chemokine signaling pathway. Moreover, 57 milk EV-proteins, mainly attributed to enzymes, cytoskeletal proteins, and transport proteins, were in the top 100 most identified EV-proteins in different species and body fluids, which might be related to the biogenesis, structure, and traffic of all vesicles. The results showed that NFFS diets could influence cow milk EV-protein composition, implying that we could take effective nutritional strategies to promote the synthesis of milk functional ingredients. Combined with all our studies, NFFS diets were recommended to improve the rumen fermentation model and enrich the milk EV proteins of dairy cows.