Milk proteins are a source of bioactive molecules for calves and humans that may also reflect the physiology and metabolism of dairy cows. Dietary
lipid supplements are classically used to modulate the
lipid content and composition of bovine milk, with potential impacts on the nutrient's homeostasis and the systemic
inflammation of cows that remains to be more explored. This study aimed at identifying discriminant
proteins and their associated pathways in twelve Holstein cows (87 ± 7 days in milk), multiparous and non-pregnant, fed for 28 d a diet either, supplemented with 5% DM intake of
corn oil and with 50% additional
starch from wheat in the concentrate (COS, n = 6) chosen to induce a milk fat depression, or with 3% DM intake of hydrogenated
palm oil (HPO, n = 6) known to increase milk fat content. Intake, milk yield and milk composition were measured. On d 27 of the experimental periods, milk and blood samples were collected and label-free quantitative proteomics was performed on
proteins extracted from plasma,
milk fat globule membrane (MFGM) and skimmed milk (SM). The
proteomes from COS and HPO samples were composed of 98, 158 and 70 unique
proteins, respectively, in plasma, MFGM and SM. Of these, the combination of a univariate and a multivariate partial least square discriminant analyses reveals that 15
proteins in plasma, 24 in MFGM and 14 in SM signed the differences between COS and HPO diets. The 15
plasma proteins were related to the immune system,
acute-phase response, regulation of
lipid transport and
insulin sensitivity. The 24 MFGM
proteins were related to the
lipid biosynthetic process and secretion. The 14 SM
proteins were linked mainly to immune response,
inflammation and
lipid transport. This study proposes discriminant milk and plasma
proteomes, depending on diet-induced divergence in milk fat secretion, that are related to nutrient homeostasis,
inflammation, immunity and lipid metabolism. The present results also suggest a higher state of
inflammation with the COS diet.