title: Short communication: indigestible markers reduce the mammary Delta9-desaturase index and alter the milk fatty acid composition in cows.
abstract: Accurate determination of the flow of nutrients at the omasum requires the use of a triple marker system. Typically, a system based on ruminal administration of the lithium salt of CoEDTA, ytterbium acetate (Yb-Ac), and chromium-mordanted straw (Cr-S) has been used. However, there is evidence to suggest that product:substrate ratios for stearoyl-coenzyme A desaturase (Delta(9)-desaturase) are lower in milk fat from cows administered a combination of CoEDTA, Yb-Ac, and Cr-S, indicating reduced Delta(9)-desaturase activity. To evaluate this hypothesis, samples of milk were collected 1 d before, and on d 2, 6, and 9 of administering the CoEDTA, Yb-Ac, and Cr-S triple marker system into the rumen of 4 cows. A 4 x 4 Latin square with 28-d experimental periods was used to assess the effects of 0, 75, 150, and 300 g/d of fish oil in the diet on ruminal and mammary lipid metabolism. Irrespective of the amount of fish oil in the diet, concentrations of all milk fatty acids containing a cis-9 double bond were reduced after markers were given. Milk fatty acid pairs dependent on Delta(9)-desaturase were decreased over time, with responses reaching a nadir within 6 d of marker administration. Overall, administering markers into the rumen was associated with a mean decrease in milk cis-9 10:1/ 10:0, cis-9 12:1/12:0, cis-9 14:1/14:0, cis-9 16:1/16:0, cis-9 17:1/17:0, cis-9 18:1/18:0, and cis-9,trans-11 conjugated linoleic acid/trans-11 18:1 concentration ratios of 44.6, 52.7, 58.7, 36.8, 37.2, 44.3, and 43.0%, respectively. In conclusion, one or more of the markers administered altered milk fatty acid composition and may act as an inhibitor of Delta(9)-desaturase in the bovine mammary gland.
authors.affiliation: Animal Production Research, MTT Agrifood Research Finland, FIN 31600, Jokioinen, Finland. kevin.shingfield@mtt.fi
authors.forename: K J
authors.initials: KJ
authors.lastname: Shingfield
authors.forename: V
authors.initials: V
authors.lastname: Toivonen
authors.forename: A
authors.initials: A
authors.lastname: Vanhatalo
authors.forename: P
authors.initials: P
authors.lastname: Huhtanen
authors.forename: J M
authors.initials: JM
authors.lastname: Griinari
mesh_terms: D000085:Acetates / Q000008:administration & dosage; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D002857:Chromium / Q000008:administration & dosage; D004063:Digestion; D004492:Edetic Acid / Q000008:administration & dosage; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D005227:Fatty Acids / Q000032:analysis*; D005260:Female; D008321:Mammary Glands, Animal / Q000201:enzymology*; D008892:Milk / Q000737:chemistry*; D012417:Rumen / Q000187:drug effects / Q000378:metabolism; D013230:Stearoyl-CoA Desaturase / Q000032:analysis* / Q000037:antagonists & inhibitors; D015018:Ytterbium / Q000008:administration & dosage
chemical_list: D000085:Acetates; D004791:Enzyme Inhibitors; D005227:Fatty Acids; D002857:Chromium; D004492:Edetic Acid; D013230:Stearoyl-CoA Desaturase; D015018:Ytterbium