title: Elevated concentrate-to-forage ratio in dairy cow rations is associated with a shift in the diameter of milk fat globules and remodeling of their membranes.
abstract: We examined the effects of concentrate-to-forage ratio in dairy cow rations on milk-fat composition, with a specific focus on the structure of milk fat globules (MFG). Twenty-four Holstein cows, 153 d in milk, were assigned to 2 dietary treatments in a crossover design study. Treatments were (1) high-concentrate (65%), low-forage (35%; HCLF) diet and (2) low-concentrate (35%), high-forage (65%; LCHF) diet. The mean diameter of the MFG; plasma concentrations of insulin, glucose, and nonesterified fatty acids (FA); and the composition and concentrations of milk FA and polar lipids were determined. Concentrations of insulin were 56% higher, and those of nonesterified FA 46% lower, in the HCLF than in the LCHF diet. The milk yield was 8.5 kg/d higher and yields of fat, protein, and lactose were 180, 350, and 403 g/d higher, respectively, in the HCLF versus LCHF diet. Milk FA composition differed between treatments, with 1.5 and 1.0 percentage units higher saturated and polyunsaturated FA concentrations, respectively, in the HCLF versus LCHF diet. Mean MFG diameter tended to be smaller (0.2 μm) in the HCLF diet than in the LCHF diet, associated with increased daily phospholipids yield (34%), lower phosphatidylserine and higher phosphatidylcholine concentrations. In conclusion, the decreased milk and fat yields in the LCHF diet were associated with remodeling of the MFG membrane and with the secretion of larger MFG. Membrane remodeling of the mammary epithelium membranes seems to play a role in regulating MFG size.
authors.affiliation: Department of Animal Science, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel. Electronic address: argov.nurit@mail.huji.ac.il.
authors.forename: Nurit
authors.initials: N
authors.lastname: Argov-Argaman
authors.affiliation: Department of Animal Science, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors.forename: Ronit
authors.initials: R
authors.lastname: Mesilati-Stahy
authors.affiliation: Department of Animal Science, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors.forename: Yogev
authors.initials: Y
authors.lastname: Magen
authors.affiliation: Department of Ruminant Science, Institute of Animal Science, ARO, The Volcani Center, POB 6 Bet-Dagan, Israel.
authors.forename: Uzi
authors.initials: U
authors.lastname: Moallem
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D018592:Cross-Over Studies; D004032:Diet / Q000662:veterinary; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified / Q000032:analysis; D005260:Female; D006017:Glycolipids / Q000032:analysis / Q000737:chemistry*; D006023:Glycoproteins / Q000032:analysis / Q000737:chemistry*; D007774:Lactation / Q000502:physiology; D066292:Lipid Droplets; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008892:Milk / Q000737:chemistry* / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; D006017:Glycolipids; D006023:Glycoproteins; C110367:milk fat globule
keywords: high-forage diet; membrane; milk fat globule; phospholipid