EFFECT OF VARIOUS LEVELS OF DUODENAL CORN STARCH INFUSION ON SMALL INTESTINAL DISAPPEARANCE AND NET GLUCOSE ABSORPTION IN GROWING-FINISHING SHEEP

In a 4×4 randomized block design, five sheep in each group fitted with ruminal, duodenal and ileal cannulas and with carotid artery, jugular vein, mesenteric and portal venous catheters were used to study effect of intraduodenlly infused starch on starch digestion, absorption in the small intestine and the glucose fluxes into and out the liver as well as the net liver glucose production. Four infused starch levels, i.e. 0, 66.39, 116.39 and 166.39g/d were used, which resulted in 33.61, 100, 150 and 200g/d of starch entering the duodenum. The results showed that as starch infused level was increased the amount of starch disappearance in the small intestine raised, and the amount of net portal glucose flux and glucagon/insulin ratio were improved, but the rate of intestinal starch disappearance was decreased with the increasing intraduodenally infused starch levels. When starch amount entering the duodenum approached to 150g/d or 200g/d, the net portal glucose flux, net liver glucose production, hepatic vein glucose flux and glucagon/insulin ratio were keeping at a flat form, which indicated that net portal glucose flux , net liver glucose production, portal vein glucose flux could be improved by increasing exogenous glucose supply. The limit for digestion and absorption of the rumen bypass starch in the small intestine of sheep might be 150g/d (11.6g/kgW0.75/d). In addition,the fact that the amount of net portal glucose flux in the sheep fed a 1.1M diet without starch infusion became negative value indicated the drained glucose amount in intestinal lumen tissues of the sheep waw more than the absorbed amount by the portal vein.The significant co-relation between the amount of starch disappearance in the small intestine and the amount of glucose consumed by PDV tissues was found, and the regression equation is:Y=12.78+0.6402X (r2=0.9164, n=20 , P0.01).