title: Effect of grazing fresh legumes or feeding silage on fatty acids and enzymes involved in the synthesis of milk fat in dairy cows.
abstract: The impact of fresh legume types or silage on the composition of milk fatty acids and transcription of enzymes involved in the synthesis of milk fat in cows was studied. Three groups of cows grazed high proportions of white clover, red clover and lucerne, respectively. A fourth group of cows was fed maize/grass silage. The cows grazing high proportions of legumes produced significantly more 18:1 trans-11, 18:2 cis9-trans11, 18:2 trans10-cis12 and 18:3 fatty acids than cows fed silage. White clover and lucerne grazing resulted in significantly lower output of 18:1 trans9 in milk than red clover grazing and maize/grass silages. Transcription of stearoyl-CoA desaturase (SCD) in mammary tissue was significantly increased by grazing high proportions of legume whereas fatty acid synthase and acetyl-CoA carboxylase were not affected by type of feeding. Furthermore, average milk fat globule diameter was correlated to daily milk fat yield but was not affected by feeding. Although the fresh forage affected the transcription of SCD in mammary tissue, the largest effects were on the trans11-based fatty acids. It is concluded that type of forage, i.e. fresh or silage, had a greater impact on rumen fermentation pattern than on transcription of enzymes involved in the synthesis of milk fat.
authors.affiliation: Department of Food Science, Faculty of Agricultural Sciences, Aarhus University, Research Centre Foulum, PO Box 50, DK-8830 Tjele, Denmark. lars.wiking@agrsci.dk
authors.forename: Lars
authors.initials: L
authors.lastname: Wiking
authors.forename: Peter K
authors.initials: PK
authors.lastname: Theil
authors.forename: Jacob H
authors.initials: JH
authors.lastname: Nielsen
authors.forename: Martin T
authors.initials: MT
authors.lastname: Sørensen
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000378:metabolism; D004032:Diet / Q000662:veterinary*; D007887:Fabaceae / Q000378:metabolism*; D064429:Fatty Acid Synthases / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis* / Q000378:metabolism; D005260:Female; D008321:Mammary Glands, Animal / Q000201:enzymology; D000455:Medicago sativa / Q000378:metabolism; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012820:Silage; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism; D029921:Trifolium / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D013230:Stearoyl-CoA Desaturase; D064429:Fatty Acid Synthases; D000103:Acetyl-CoA Carboxylase