Weiss W P, Smith K L, Hogan J S, Steiner T E
Department of Dairy Science, Ohio Agricultural Research and Development Center, Ohio State University, Wooster 44691, USA.
J Dairy Sci. 1995 Aug;78(8):1837-42. doi: 10.3168/jds.S0022-0302(95)76808-4.
The effects of forage to concentrate ratio and the commercial form of vitamins A and E on in vitro ruminal disappearance of retinol and alpha-tocopherol were studied. Ruminally fistulated cows were fed diets with either 80 or 50% forage. In vitro substrates that were similar to those fed to the donor cows were incubated with buffered ruminal fluid for 24 h. Different commercial forms of vitamin E (spray-dried, silicic acid adsorbate, and lipid-encased forms) and vitamin A (gelatin beadlet and lipid-encased forms) were added to the flasks. The vitamin E was all-rac-alpha-tocopheryl acetate, and the vitamin A was all-trans-retinyl acetate. The amount of alpha-tocopherol in the flasks was not affected by diet or form of vitamin E and did not change over the 24-h incubation. Retinol disappearance was not affected by form of vitamin A but was substantially higher for the 50% forage diet than for the 80% forage diet (72 vs. 20% at 24 h). These data suggest that ruminal metabolism of vitamin E is minimal and not affected by forage to concentrate ratio. Additionally, vitamin A destruction in the rumen was much higher when cows were fed a typical lactation diet than when fed a typical dry cow diet.
研究了饲草与精料比例以及维生素A和E的商业形式对瘤胃中视黄醇和α-生育酚体外消失率的影响。给瘤胃造瘘的奶牛饲喂含80%或50%饲草的日粮。将与供体奶牛所喂日粮相似的体外底物与缓冲瘤胃液一起孵育24小时。向培养瓶中添加不同商业形式的维生素E（喷雾干燥型、硅酸吸附型和脂质包裹型）和维生素A（明胶微囊型和脂质包裹型）。维生素E为全反式α-生育酚乙酸酯，维生素A为全反式视黄醇乙酸酯。培养瓶中α-生育酚的含量不受日粮或维生素E形式的影响，在24小时的孵育过程中也没有变化。视黄醇的消失率不受维生素A形式的影响，但50%饲草日粮的视黄醇消失率显著高于80%饲草日粮（24小时时分别为72%和20%）。这些数据表明，维生素E在瘤胃中的代谢极少，且不受饲草与精料比例的影响。此外，与饲喂典型干奶牛日粮相比，奶牛饲喂典型泌乳日粮时瘤胃中维生素A的破坏程度要高得多。
