Pancreatic secretion and intestinal digestibility of amino acids in chicken at different dietary protein level and quality

The improvement of feed conversion into the products in poultry production is primarily related to the effectiveness of digestion and assimilation of dietary protein and therefore sets specific requirements on its nutritive value and profile of limiting amino acids, and on the availability of amino acids for absorption and subsequent metabolization. Digestibility and absorbability of amino acids were recently studied in pigs (E.N. Golovko, 2011) and poultry (P. Dalibard et al., 1995; A.E. Yapontsev, 2016) using the concepts of apparent and standardized ileal digestibility. Ileal digestibility is defined as the difference between consumed amounts of amino acids and the unabsorbed residues at the level of distal end of the ileum. Data on ileal digestibility rates allow optimization of dietary protein quality, digestive function and appetite (V. Ryadchikov et al., 2010). Our earlier studies showed that secretory function of the pancreas in adult chicken and broiler chicks can adjust to the changes in dietary amino acid balance; when dietary level of limiting amino acid (lysine) reached the recommended level the enzymatic activities in pancreatic juice grew substantially (Ts.Zh. Batoev, et al., 1990; V.G. Vertiprakhov, 2015). In this study we have experimentally found differences between enzymatic activities in pancreatic juice and ileal chymus and ileal amino acid digestibility in chronically fistulated chickens which were fed diets of different protein levels. Control diet was standard wheat-based, and experimental diet was supplemented with poorly hydrolysable ingredients (wheat bran, sunflower cake) contained lower levels of crude protein and energy. When chickens were fed with experimental diet instead of control one the decreases in proteolytic activity in pancreatic juice by 22-36 % and in ileal chymus by 34 % (compared to control) were found. Data on ileal digestibility of amino acids showed that intestinal digestion of amino acids is more effective at higher dietary protein level; this effect can be related to the increase in enzymatic activities of digestive juices in response to the increase in dietary protein, and to the concomitant improvement in feed palatability.