Department of Animal Health and Bioscience, Aarhus University, Faculty of Agricultural Sciences, DK-8830 Tjele, Denmark.
J Dairy Sci. 2010 Dec;93(12):5748-57. doi: 10.3168/jds.2010-3338.
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.
研究了奶牛瘤胃中脂溶性维生素 D 和 E 的命运。通过瘤胃瘘管从每头奶牛中取出 10 到 15 公斤瘤胃液。取出一个样品（0 小时样品），其余的内容物与 4360 毫克全-rac-α-生育酚乙酸酯（维生素 E；研究 1）或 4360 毫克全-rac-α-生育酚乙酸酯、250 毫克麦角钙化醇（维生素 D(2)）和 250 毫克胆钙化醇（维生素 D(3)）混合。混合后，将瘤胃液重新返回给各自的奶牛。在向瘤胃中引入维生素后 0、6、24 和 30 小时采集血液。在 0、1、2、4、6、24 和 30 小时（体内）采集瘤胃液样品。从 1 小时的样品中，从每头奶牛中取出 6 个样本，在 37°C 下孵育，并在 2、4、6、12、24 和 30 小时（体外）取出。由于进食和通过瘤胃排出的稀释作用，添加的α-生育酚、麦角钙化醇和胆钙化醇在瘤胃中的体内浓度最初增加，随后下降。与总生育酚含量相比，来自饲料中天然含量的游离醇形式的α-生育酚水平在整个体内研究中保持不变，这表明在瘤胃中没有发生乙酸酯形式向醇形式的水解。在体外，所有添加的维生素都以恒定水平存在；因此，在瘤胃液中没有降解任何添加的维生素。与每毫克添加的麦角钙化醇或胆钙化醇代谢物的增加相比，每毫克添加的α-生育酚在 24 小时内以毫克为单位，血液中α-生育酚的浓度增加率低于血浆中α-生育酚的浓度增加率。总之，麦角钙化醇、胆钙化醇和乙酸生育酚酯在瘤胃中和高产奶牛的瘤胃液中均稳定。与向瘤胃中引入的维生素量相比，维生素在血浆中的浓度变化表明，麦角钙化醇对血浆状态的影响小于胆钙化醇，α-生育酚的影响甚至更小。单次给予α-生育酚乙酸酯后，血浆反应有限，这导致口服单次给予全-rac-α-生育酚乙酸酯的生理价值有限的结论。
