Effects of energy and amino acid supply to the small intestine on amino acid metabolism

Effects of increasing the supply of starch and amino acids in the small intestine on absorption of nutrients and concentration of plasma metabolites were determined. A 2 × 2 × 2 factorial arrangement of treatments was used and dietary factors were as follows: 1) 25% versus 50% dietary corn, 2) formaldehyde-treated (rumen-protected) versus untreated corn, and 3) supplemental rumen-protected methionine and lysine versus no supplemental amino acids. Treatments were randomly allotted to 40 individually fed steers for the trial. Feeding formaldehyde-treated corn resulted in increased plasma glucose and insulin concentrations. Plasma insulin and glucose concentrations were also directly proportional to dietary corn level. The plasma concentrations of urea and most individual amino acids were markedly decreased when steers were fed treated corn compared with those fed untreated corn. Increased postruminal nutrient supply enhanced metabolic utilization of amino acids in these steers.