Amino Acid Patterns during Digestion in the Small Intestine of Ducks

Abstract

Total nitrogen and amino acid patterns were studied in five equal segments of intestine of ducks fed rations of known amino acid composition ad libitum. The largest quantities of free amino acids were found in the middle segment extending from 41 to 60% of intestinal length. Total quantity of nitrogen was highest in the first two segments and decreased markedly in more distal segments. The pattern of free amino acids in the intestinal segments reflected the pattern of the dietary protein, particularly in the mid-20% of the intestine. This was demonstrated by feeding diets in which the protein was either a combination of corn and soybean meal or of corn and corn gluten meal. The pattern of amino acids in segments more distal to the midpoint did not reflect the dietary amino acid pattern as well as that in upper portions, but was similar to that observed when a nitrogen-free diet was fed. This suggests that digestion of dietary proteins occurs before that of endogenous protein. The dilution of dietary protein by endogenous protein was insufficient to mask the amino acid pattern of ingested protein.