Grain Proteins Digested by Trypsin Modify Plasma Amino Acid Concentration in Chickens

The aim of this study was to examine the influence of three kinds of grain proteins digested by trypsin on plasma glucose and amino acid concentrations in young chickens. At first, we examined the time course change in the absorption of glucose and amino acids from small intestine after oral administration of glucose and amino acid solution. At 0, 20, 40, 60, 80, 100 and 120 min after administration, blood samples were taken from the mesenteric vein, and plasma concentrations of glucose and amino acids were measured. Plasma glucose concentration reached to the highest value at 20 min after oral administration, and this value was remained until 120 min. Most of amino acids were showed the highest concentration at 20 min after oral administration. Secondly, the influence of trypsin-digested grain proteins on the absorption of glucose and amino acids from small intestine was examined. Wheat gluten, corn zein and soybean protein were digested by trypsin, and each digested protein was mixed with glucose and amino acid solution. At 20 min after oral administration of mixture solution, blood samples were taken from mesenteric vein. Plasma glucose level was not affected by any protein digesta. The digesta of soybean protein elevated plasma level of histidine compared to that of corn zein. The digesta of wheat gluten increased plasma concentrations of both phenylalanine and proline compared to the control. Thirdly, the interactive effect of glucose and wheat gluten digesta on the absorption of amino acids from small intestine was examined. The increase in the absorption of amino acids by wheat gluten digesta was not influenced by oral administration of glucose. These results suggest that the digesta of grain proteins has the potency to modify the absorption of amino acids from small intestine of chickens.