Shingfield K J, Ahvenjärvi S, Toivonen V, Vanhatalo A, Huhtanen P, Griinari J M
Animal Production Research, MTT Agrifood Research Finland, Jokioinen, Finland.
Br J Nutr. 2008 May;99(5):971-83. doi: 10.1017/S0007114507853323. Epub 2007 Nov 16.
Based on the potential benefits of cis-9, trans-11-conjugated linoleic acid (CLA) for human health there is interest in developing sustainable nutritional strategies for enhancing the concentration of this fatty acid in ruminant-derived foods. Most evidence to date suggests that endogenous synthesis is the major source of cis-9, trans-11 in milk fat and ruminal outflow is limited and largely independent of dietary 18 : 2n-6 supply. Four lactating cows fitted with a rumen cannula were used in a 4 x 4 Latin square with 14 d experimental periods to examine the effects of sunflower-seed oil (SFO) as a source of 18 : 2n-6 on ruminal lipid metabolism. Cows were offered grass silage-based diets supplemented with 0, 250, 500 or 750 g SFO/d. Supplements of SFO had no effect on DM intake, milk fat or protein secretion, but increased linearly (P < 0.01) milk yield and milk lactose output and shifted (P < 0.001) rumen fermentation towards propionate at the expense of acetate. SFO supplements increased linearly (P < 0.05) the flow of 18 : 0, 18 : 1, 18 : 2n-6 and total CLA at the omasum and enhanced ruminal cis-9-18 : 1, 18 : 2n-6 and 18 : 3n-3 metabolism. Flows of all-trans- (Delta4-16) and cis- (Delta9-16) 18 : 1 isomers were elevated, while increases in ruminal CLA outflow were confined to trans-8, trans-10 and geometric 9,11 and 10,12 isomers. It is concluded that supplementing grass silage-based diets with plant oils rich in 18 : 2n-6 enhances ruminal outflow of trans-11-18 : 1 and cis-9, trans-11-CLA in lactating cows.
鉴于顺-9，反-11-共轭亚油酸（CLA）对人类健康具有潜在益处，人们对制定可持续的营养策略以提高反刍动物源性食品中这种脂肪酸的浓度很感兴趣。迄今为止的大多数证据表明，内源性合成是乳脂肪中顺-9，反-11的主要来源，瘤胃流出物有限且在很大程度上独立于日粮18:2n-6的供应。选用四头装有瘤胃瘘管的泌乳奶牛，采用4×4拉丁方设计，试验期为14天，以研究作为18:2n-6来源的葵花籽油（SFO）对瘤胃脂质代谢的影响。给奶牛提供以青贮草为基础的日粮，分别补充0、250、500或750克/天的SFO。补充SFO对干物质采食量、乳脂肪或蛋白质分泌没有影响，但使产奶量和乳糖产量呈线性增加（P<0.01），并使瘤胃发酵向丙酸方向转变（P<0.001），同时乙酸减少。补充SFO使瘤胃和网胃中18:0、18:1、18:2n-6和总CLA的流量呈线性增加（P<0.05），并增强了瘤胃中顺-9-18:1、18:2n-6和18:3n-3的代谢。全反式（Δ4-16）和顺式（Δ9-16）18:1异构体的流量增加，而瘤胃CLA流出量的增加仅限于反式-8，反式-10以及几何异构体9,11和10,12。得出的结论是，在以青贮草为基础的日粮中添加富含18:2n-6的植物油可提高泌乳奶牛瘤胃中反式-11-18:1和顺-9，反-11-CLA的流出量。
