EFFECT OF STARCH ON THE BIOAVAILABILITY OF GLUTAMINE AND LEUCINE IN THE DAIRY-COW

This experiment was designed to quantify changes in utilization of Gln and Leu by the gut wall as a result of changes in the starch supply t o the duodenum. Four dairy cows fitted with cannulas in the rumen and the distal duodenum were adapted for 3 wk to starch infusion, either i nto the rumen (600 g/d of flaked maize) or into the duodenum (300 g/d of flaked maize plus 300 g/d of maize meal), in a 2 x 2 crossover desi gn. Absorption and elimination kinetics and the relative bioavailabili ty of Gin and Leu were measured during wk 4 and 5. After infusion of 5 0 g of Gln or 10 g of Leu into the duodenum or jugular vein, blood sam ples were taken from the jugular vein at 0.5-h intervals up to 4 h aft er infusion. Concentrations of Gln and Leu in plasma fitted best to an open, one-compartment model (duodenal infusion) or to an open, two-co mpartment model (i.v. infusion). Both amino acids were rapidly absorbe d; half-life times were less than 20 min. The amount of Gin trapped in the splanchnic bed was higher than the amount of Leu trapped in the s planchnic bed. Site of starch infusion did not affect the relative bio availability of amino acids.