title: Diet-induced milk fat depression is associated with alterations in ruminal biohydrogenation pathways and formation of novel fatty acid intermediates in lactating cows.
abstract: The biohydrogenation theory of milk fat depression (MFD) attributes decreases in milk fat in cows to the formation of specific fatty acids (FA) in the rumen. Trans-10, cis-12-CLA is the only biohydrogenation intermediate known to inhibit milk fat synthesis, but it is uncertain if increased ruminal synthesis is the sole explanation of MFD. Four lactating cows were used in a 4×4 Latin square with a 2×2 factorial arrangement of treatments and 35-d experimental periods to evaluate the effect of diets formulated to cause differences in ruminal lipid metabolism and milk fat synthesis on the flow of FA and dimethyl acetal at the omasum. Treatments comprised total mixed rations based on grass silage with a forage:concentrate ratio of 35:65 or 65:35 containing 0 or 50 g/kg sunflower oil (SO). Supplementing the high-concentrate diet with SO lowered milk fat synthesis from -20·2 to -31·9 % relative to other treatments. Decreases in milk fat were accompanied by alterations in ruminal biohydrogenation favouring the trans-10 pathway and an increase in the formation of specific intermediates including trans-4 to trans-10-18 : 1, trans-8, trans-10-CLA, trans-9, cis-11-CLA and trans-10, cis-15-18 : 2. Flow of trans-10, cis-12-CLA at the omasum was greater on high- than low-concentrate diets but unaffected by SO. In conclusion, ruminal trans-10, cis-12-CLA formation was not increased on a diet causing MFD suggesting that other biohydrogenation intermediates or additional mechanisms contribute to the regulation of fat synthesis in the bovine mammary gland.
authors.affiliation: 1Nutritional Physiology,Green Technology,Natural Resources Institute Finland (Luke),FI-31600 Jokioinen,Finland.
authors.forename: Laura
authors.initials: L
authors.lastname: Ventto
authors.affiliation: 1Nutritional Physiology,Green Technology,Natural Resources Institute Finland (Luke),FI-31600 Jokioinen,Finland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Leskinen
authors.affiliation: 1Nutritional Physiology,Green Technology,Natural Resources Institute Finland (Luke),FI-31600 Jokioinen,Finland.
authors.forename: Piia
authors.initials: P
authors.lastname: Kairenius
authors.affiliation: 1Nutritional Physiology,Green Technology,Natural Resources Institute Finland (Luke),FI-31600 Jokioinen,Finland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Stefański
authors.affiliation: 1Nutritional Physiology,Green Technology,Natural Resources Institute Finland (Luke),FI-31600 Jokioinen,Finland.
authors.forename: Ali R
authors.initials: AR
authors.lastname: Bayat
authors.affiliation: 2Animal Genomics,Green Technology,Natural Resources Institute Finland (Luke),FI-31600 Jokioinen,Finland.
authors.forename: Johanna
authors.initials: J
authors.lastname: Vilkki
authors.affiliation: 1Nutritional Physiology,Green Technology,Natural Resources Institute Finland (Luke),FI-31600 Jokioinen,Finland.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Shingfield
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle; D004032:Diet; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D019587:Dietary Supplements; D004063:Digestion; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D006865:Hydrogenation; D007774:Lactation / Q000378:metabolism*; D044243:Linoleic Acids, Conjugated / Q000378:metabolism*; D050356:Lipid Metabolism; D008892:Milk / Q000378:metabolism*; D009851:Omasum; D010938:Plant Oils / Q000378:metabolism / Q000494:pharmacology; D012417:Rumen / Q000378:metabolism*; D012820:Silage; D000074242:Sunflower Oil
chemical_list: D004041:Dietary Fats; D005227:Fatty Acids; D044243:Linoleic Acids, Conjugated; D010938:Plant Oils; D000074242:Sunflower Oil
keywords:  DMA dimethyl acetal;  FA fatty acid;  FAME fatty acid methyl ester;  FC forage to concentrate;  H high-concentrate diet containing no added oil;  HSO high-concentrate diet containing 50 g sunflower oil/kg diet DM;  L low-concentrate diet containing no added oil;  LSO low-concentrate diet containing 50 g sunflower oil/kg diet DM;  MFD milk fat depression;  OBCFA odd- and branched-chain fatty acids;  SO sunflower oil; Biohydrogenation; Conjugated fatty acids; Cows; Milk fat; Rumen