Short communication: Diets supplemented with starch and corn oil, marine algae, or hydrogenated palm oil differently affect selected metabolite concentrations in cow and goat milk

摘要

The objective was to investigate the effects of species(cow vs. goat) and of various dietary lipid supplements,known to modulate milk fat content, on selectedmetabolites and enzymes in milk and to explore theircorrelations with performance traits. Twelve Holsteincows and 12 Alpine goats, all multiparous and nonpregnant,and at 86 ± 24.9 and 61 ± 1.8 DIM, respectively,were fed a basal diet (45% forage + 55% concentrate)not supplemented (CTL) or supplemented with corn oilplus wheat starch [COS, 5% of diet dry matter (DM)],marine algae powder (MAP, 1.5% of diet DM), or hydrogenatedpalm oil (HPO, 3% of diet DM) in a replicated4 × 4 Latin square design with 28-d experimentalperiods. Intake, milk production and composition, milkfatty acid profile, and plasma metabolite concentrationswere previously reported. Concentrations of 9milk metabolites [β-hydroxybutyrate (BHB), glucose,glucose-6-phosphate, isocitrate, choline, glutamate,urea, cholesterol, and free amino groups] and 2 milkenzyme activities (alkaline phosphatase and lactatedehydrogenase) were measured on d 24 of each experimentalperiod. Dairy performance data showed markedspecies and diet effects on milk fat content. Irrespectiveof diet, cow milk was richer in alkaline phosphatase andglucose compared with goat milk (16 and 3 times more,respectively), whereas goat milk had greater urea andglucose-6-phosphate concentrations compared with cowmilk (1.9 and 5.3 times more, respectively). In cows,COS decreased milk BHB and choline (−25 and −43%,respectively) compared with CTL, whereas no effectswere observed in goats. The COS and MAP diets increasedmilk isocitrate compared with CTL in cows, butCOS decreased isocitrate concentrations in goat milk.Milk choline was correlated with milk fat content incows (Spearman r, r_s = +0.73) and goats (r_s = +0.58),and lactate dehydrogenase activity was correlated withmilk somatic cell count (r_s = +0.66) in cows but not ingoats. We provide evidence of different milk metaboliteresponses according to species and diets. Metabolitesand enzymes secreted in milk may be indicators ofspecificities of lipid metabolism among ruminant speciesand may contribute to a better understanding ofmechanisms regulating milk fat secretion. Changesin the concentrations of some metabolites consideredminor components of milk may be valuable diagnostictools of mammary gland and animal metabolism as wellas of milk processing characteristics.