Effect of intravenous glucose infusion on metabolism of portal-drained viscera in sheep fed a cereal/straw-based diet.

This experiment investigated the effect of intrajugular infusion of glucose on whole-body glucose metabolism and the absorption of nutrients by the portal-drained viscera of four Suffolk-cross sheep, average BW 46 +/- 7 kg, fed a cereal/straw-based pelleted diet. Each sheep received by random allocation 0 (control), 1.0, or 2.0 mg of glucose.kg BW-1.min-1 for 8 h infused into the jugular vein. Glucose irreversible loss rate, measured by simultaneous infusion of 6-[3H]-glucose, increased approximately stoichiometrically during glucose infusion (.51, .75, and 1.09 error mean square [EMS] .032 mmol/min for control, 1.0, and 2.0 mg of glucose infused.kg BW-1.min-1, respectively). Utilization of glucose increased in portal tissues (P = .089) as a result of glucose infusion (.17, .18, and .33 EMS .008 mmol/min) and was a constant proportion of glucose irreversible loss (.28). Portal blood flow was not affected by glucose infusion (overall mean 1.13 L/min EMS .034). Net portal absorption of acetate increased during glucose infusion although ruminal VFA concentrations were not affected. In contrast, net free amino acid absorption by portal-drained tissues was reduced during glucose infusion (291, 115, and 4 EMS 33,816 mumol/min, P = .054). These results show that metabolism of nutrients across the gut wall is influenced by glucose availability to gastrointestinal tissues and affects the pattern of nutrients available to the liver and peripheral tissues.