INRA, UMR1289 Tissus Animaux Nutrition Digestion Ecosystème et Métabolisme, F-31326 Castanet-Tolosan, France.
J Dairy Sci. 2012 Oct;95(10):5916-26. doi: 10.3168/jds.2012-5326. Epub 2012 Aug 15.
Among trans fatty acids, trans-10,cis-12 CLA has negative effects on cow milk fat production and can affect human health. In high-yielding dairy cows, a shift from the trans-11 to the trans-10 pathway of biohydrogenation (BH) can occur in the rumen of cows receiving high-concentrate diets, especially when the diet is supplemented with unsaturated fat sources. In some but not all experiments, vitamin E has been shown to control this shift. To ascertain the effects of vitamin E on this shift of BH pathway, 2 studies were conducted. The first study explored in vitro the effects of addition of natural (RRR-α-tocopherol acetate) and synthetic (dl-α-tocopherol acetate) vitamin E. Compared with control and synthetic vitamin E, the natural form resulted in a greater trans-10/trans-11 ratio; however, the effect was very low, suggesting that vitamin E was neither a limiting factor for rumen BH nor a modulator of the BH pathway. An in vivo study investigated the effect of natural vitamin E (RRR-α-tocopherol) on this shift and subsequent milk fat depression. Six rumen-fistulated lactating Holstein cows were assigned to a 2×2 crossover design. Cows received 20-kg DM of a control diet based on corn silage with 22% of wheat, and after 2 wk of adaptation, the diet was supplemented with 600 g of sunflower oil for 2 more weeks. During the last week of this 4-wk experimental period, cows were divided into 2 groups: an unsupplemented control group and a group receiving 11 g of RRR-α-tocopherol acetate per day. A trans-10 shift of ruminal BH associated with milk fat depression due to oil supplementation of a high-wheat diet was observed, but vitamin E supplementation of dairy cows did not result in a reversal toward a trans-11 BH pathway, and did not restore milk fat content.
在反式脂肪酸中，反式-10，顺式-12CLA 对奶牛乳脂生产有负面影响，并可能影响人类健康。在高产奶牛中，当奶牛摄入高浓缩饲料时，瘤胃中生物氢化（BH）的反式-11 途径会向反式-10 途径转移，特别是当饮食中补充不饱和脂肪源时。在一些但不是所有的实验中，已经表明维生素 E 可以控制这种 BH 途径的转变。为了确定维生素 E 对这种 BH 途径转变的影响，进行了两项研究。第一项研究探讨了添加天然（RRR-α-生育酚醋酸酯）和合成（dl-α-生育酚醋酸酯）维生素 E 对体外 BH 的影响。与对照和合成维生素 E 相比，天然形式导致反式-10/反式-11 比值增加；然而，效果非常低，表明维生素 E 既不是瘤胃 BH 的限制因素，也不是 BH 途径的调节剂。一项体内研究调查了天然维生素 E（RRR-α-生育酚）对这种转变以及随后乳脂减少的影响。将 6 头瘤胃瘘管泌乳荷斯坦奶牛分配到 2×2 交叉设计中。奶牛接受 20-kg DM 的基于玉米青贮的对照日粮，其中含有 22%的小麦，适应 2 周后，日粮再补充 600 g 葵花籽油，再适应 2 周。在这 4 周实验期的最后一周，奶牛分为两组：未补充对照组和每天补充 11 g RRR-α-生育酚醋酸酯的组。高小麦日粮添加油导致瘤胃 BH 的反式-10 转移，随之出现乳脂减少，但奶牛补充维生素 E 并没有导致 BH 向反式-11 途径逆转，也没有恢复乳脂含量。
