title: Stability in the rumen and effect on plasma status of single oral doses of vitamin D and vitamin E in high-yielding dairy cows.
abstract: The ruminal fate of the fat-soluble vitamins D and E was studied in dairy cows. Ten to 15 kg of ruminal contents was taken from each cow through a ruminal fistula. A sample was taken out (0-h sample) and the rest of the contents were mixed with 4,360 mg of all-rac-α-tocopheryl acetate (vitamin E; study 1) or 4,360 mg of all-rac-α-tocopheryl acetate, 250 mg of ergocalciferol (vitamin D(2)), and 250 mg of cholecalciferol (vitamin D(3); study 2). After mixing, the ruminal contents were returned to the respective cows. Blood was collected 0, 6, 24, and 30 h after introducing the vitamins into the rumen. Samples of ruminal contents were collected at 0, 1, 2, 4, 6, 24, and 30 h (in vivo). From the 1-h sample, 6 subsamples from each cow were incubated at 37 °C and taken out at 2, 4, 6, 12, 24, and 30 h (in vitro). In vivo concentrations of added α-tocopherol, ergocalciferol, and cholecalciferol in the rumen first increased and subsequently declined due to dilution effects of eating and passage out of the rumen. The level of the free-alcohol form of α-tocopherol from the natural content in feed was constant throughout the in vivo study, in contrast to the content of total α-tocopherol, which indicated that no hydrolysis of the acetate form into alcohol form happened in the rumen. In vitro, all added vitamins were found at constant levels; hence, none of the added vitamins were degraded in ruminal contents. The concentration of α-tocopherol in plasma increased at a rate per milligram of ruminally introduced α-tocopherol below the rate of the increase in plasma ergocalciferol or cholecalciferol metabolites per milligram of introduced ergocalciferol or cholecalciferol, respectively, over 24h. In conclusion, ergocalciferol, cholecalciferol, and α-tocopheryl acetate proved to be stable in the rumen and in ruminal contents from high-yielding dairy cows. Changes in plasma concentrations of the vitamins relative to the amount of vitamin introduced to the rumen indicated a lower effect on plasma status of ergocalciferol than of cholecalciferol, and an even lower effect of α-tocopherol. The limited plasma response after a single dose of α-tocopheryl acetate led to the conclusion that oral single dose therapy with all-rac-α-tocopheryl acetate is of limited physiological value.
authors.affiliation: Department of Animal Health and Bioscience, Aarhus University, Faculty of Agricultural Sciences, DK-8830 Tjele, Denmark. Lone.Hymoller@agrsci.dk
authors.forename: L
authors.initials: L
authors.lastname: Hymøller
authors.forename: S K
authors.initials: SK
authors.lastname: Jensen
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood / Q000378:metabolism*; D002762:Cholecalciferol / Q000097:blood; D016154:Digestive System Fistula / Q000662:veterinary; D004872:Ergocalciferols / Q000097:blood; D005260:Female; D007774:Lactation; D008892:Milk / Q000378:metabolism; D012417:Rumen / Q000378:metabolism*; D014807:Vitamin D / Q000008:administration & dosage / Q000097:blood*; D014810:Vitamin E / Q000008:administration & dosage / Q000097:blood*; D014815:Vitamins / Q000008:administration & dosage / Q000097:blood*; D024502:alpha-Tocopherol / Q000097:blood
chemical_list: D004872:Ergocalciferols; D014815:Vitamins; D014807:Vitamin D; D014810:Vitamin E; D002762:Cholecalciferol; D024502:alpha-Tocopherol