Animal Sciences Group, Wageningen UR, Lelystad, The Netherlands.
J Anim Physiol Anim Nutr (Berl). 2010 Jun;94(3):319-29. doi: 10.1111/j.1439-0396.2008.00911.x. Epub 2009 Aug 3.
An in vivo experiment was performed to determine the effect of level of maize starch in the diet on digestion and site of digestion of organic matter, starch and neutral detergent fibre (NDF). In a repeated change-over design experiment, three cows fitted with a rumen cannula and T-piece cannulae in duodenum and ileum received a low-starch (12% of ration dry matter) and a high-starch (33% of ration dry matter) diet. Starch level was increased by exchanging dried sugar beet pulp by ground maize. After a 2-week adaptation period, feed intake, rumen fermentation parameters (in vivo and in situ), intestinal flows, faecal excretion of organic matter, starch and NDF were estimated. When the high-starch diet was fed, dry matter intake was higher (19.0 kg/day vs. 17.8 kg/day), and total tract digestibility of organic matter, starch and NDF was lower when the low-starch diet was fed. Maize starch concentration had no significant effect on rumen pH and volatile fatty acid concentration nor on the site of digestion of organic matter and starch and rate of passage of ytterbium-labelled forage. On the high-starch diet, an extra 1.3 kg of maize starch was supplied at the duodenum in relation to the low-starch diet, but only an extra 0.3 kg of starch was digested in the small intestine. Digestion of NDF was only apparent in the rumen and was lower on the high-starch diet than on the low-starch diet, mainly attributed to the reduction in sugar beet pulp in the high-starch diet. It was concluded that without the correction for the reduction in NDF digestion in the rumen, the extra supply of glucogenic (glucose and propionic acid) and ketogenic nutrients (acetic and butyric acid) by supplemented starch will be overestimated. The mechanisms responsible for these effects need to be addressed in feed evaluation.
进行了一项体内实验，以确定日粮中玉米淀粉水平对有机物、淀粉和中性洗涤纤维（NDF）消化和消化部位的影响。在重复交叉设计实验中，三头安装有瘤胃套管和十二指肠及回肠 T 型套管的奶牛，分别接受低淀粉（日粮干物质的 12%）和高淀粉（日粮干物质的 33%）日粮。通过用磨碎的玉米替代干糖甜菜浆来增加淀粉水平。经过 2 周的适应期，估计了饲料采食量、瘤胃发酵参数（体内和原位）、肠道流量、粪便中有机物、淀粉和 NDF 的排泄量。当饲喂高淀粉日粮时，干物质采食量更高（19.0 公斤/天比 17.8 公斤/天），而低淀粉日粮时，有机物、淀粉和 NDF 的全肠道消化率更低。玉米淀粉浓度对瘤胃 pH 值和挥发性脂肪酸浓度以及有机物和淀粉的消化部位和示踪铱标记饲料的通过速率均无显著影响。在高淀粉日粮中，与低淀粉日粮相比，十二指肠额外供应了 1.3 公斤的玉米淀粉，但只有 0.3 公斤的淀粉在小肠中被消化。NDF 的消化仅在瘤胃中明显，并且在高淀粉日粮中低于低淀粉日粮，这主要归因于高淀粉日粮中糖甜菜浆的减少。结论是，如果不对瘤胃中 NDF 消化减少进行校正，补充淀粉提供的生糖（葡萄糖和丙酸）和生酮营养物质（乙酸和丁酸）的额外供应将被高估。需要在饲料评估中解决这些影响的机制。
