Effects of Dietary Carbohydrate and of Intestinal Microflora on Excretion of Endogenous Amino Acids by Poultry

Abstract

The effects of dietary carbohydrate and of intestinal microflora on excretion of endogenous amino acids by poultry were investigated. Excretion of endogenous amino acids was compared among fasted roosters, intact roosters fed low- or high-fiber, N-free diets, and surgically-modified (SM) roosters fed a low-fiber, N-free diet. The low-fiber diet contained 50% corn starch, 45% glucose, and 5% cellulose, whereas the high-fiber diet contained 25% each of corn starch, glucose, and raw potato starch, 17.5% cellulose, and 7.5% pectin. Digesta were obtained from the terminal ileum of SM roosters to eliminate effects of the microflora in the large intestine and ceca. The roosters were force-fed 60 g of the appropriate diet (30 g at the initiation of the trial followed by an additional 30 g 6 hours later). Excreta or digesta and urine were collected quantitatively for 48 hr after the first force-feeding. Roosters fed the high-fiber diet excreted substantially more (P<.05) amino acids than did fasted roosters or roosters fed a low-fiber diet. Excreta from roosters fed the high-fiber diet contained higher (P<.05) levels of alanine and aspartic acid than excreta from fasted or digesta from SM roosters, indicating substantial microbial synthesis of amino acids in the gut. In contrast, amino acid composition of excreta from fasted and intact roosters fed the low-fiber diet was similar to that of digesta from SM roosters, suggesting less microbial influence. Excretion of glucosamine plus galactosamine by SM roosters was approximately twice that of intact roosters fed the same diet. Glycine was the most abundant amino acid in digesta of SM roosters.Results of this study indicate that dietary carbohydrate substantially affects excretion of endogenous amino acids by poultry and that fasted birds may not provide an accurate estimate of endogenous amino acid excretion for birds fed high-fiber feedstuffs in amino acid digestibility trials.