Abstract
In order to characterize the properties of protein sources, we prepared extruded pellets (EPs) which were composed of only a single protein source: fish meal (FM), pork meal (PM), blood meal (BM), corn meal (CM), soybean protein concentrate (SP), or soybean meal (SM), evaluated the gastric evacuation rate (GER) of red seabream Pagrus major juveniles, and determined the degree of undigested protein of the test EPs with gut enzyme extract. GER was highest in SM diet among the test EPs in order SM>BM>SP>CM>FM>PM diets, and SP diet tended to have a high GER value, suggesting that the soybean protein advances gastric evacuation. BM and SM diets had a low degree of digestion with gut enzyme extract, and this was due to their inhibitory activities. These diets had higher GER, suggesting that a high amount of indigestible protein in the diet may promote gastric evacuation. The concentration of triglycerides and free amino acids in serum of red seabream fed test EPs was measured as an index of absorption of dietary nutrients. The triglyceride and free amino acid levels showed different patterns depending on the protein source. These results suggest that the protein sources influence protein and lipid digestion and absorption.
