The Primary Studies On Digestive Enzymes Of Yellow Catfish (Pelteobagrus Fulvidraco)

The physico-chemical characters of digestive enzymes and the effect of different level of protein on growth, apparent digestibility and digestive enzymes activities of yellow catfish were studied in this paper. The results are as follows.1. The optimum pH of trypsin activity is 8.5-9.0, pepsin is 2.0-2.5, protease is 8.5-9.0 and amlyase is 7.5-8.5. The optimum temperature of pepsin is 35C-40C, protease is 55C-60C and amlyase is 35C-40C. The concentration of substrate for pepsin is 2.0% heamoglobin, for protease is 2.0% casin, for amylase is 1.0% dissolvable starch.2. Specific growth rate, apparent digestibility for dry matter and apparent digestibility for protein of yellow catfish increased with the increasing protein content in the diets.3. At the first 20ds of the test, typsin activity of high protein content feed group is the highest in foregut, during the later period of the test (30d-45d) , which in pancreas is the highest. During the whole period of the test, different protein content feed group have no significant effect on the distribution of pepsin, protease and amylase activities of yellow catfish, respectively that in stomach, foregut and pancreas are highest.4. During the whole period of the test, the effect of different protein content feed groups on typsin activities of yellow catfish are as fellows. In pancreas, typsin activity decreases at the beginning of the test, afterl0d it begins to increase. In foregut, in the whole period of the test, the tendency of typsin activity of yellow catfish in high protein content feed group is to decrease, however, the trend of the typsin activity in intermediate and low protein content groups are to decrease at the beginning of the test (0d-10d), then to increase (10d-45d).5. In 0d-20d, pepsin activity in stomach of yellow catfish for three different protein content groups display as fellows, pepsin activity in intermediate protein content group is higher than those in low protein content group and high protein content group. While during 30d-45d of the test, pepsin activity is increasing with the increasing protein content. Amylase activities of yellow catfish in pancrean have no significant differences in three protein content feed groups. During the later period of the test, amylase activity in foregut of intermediate protein content feed group is significantly higher than that of high protein content group. At the end of the test, amylase activity in foregut and hindgut ofintermediate protein content group is highest in three groups, next is in protein content group, and the smallest is that in high protein content group.