EFFECT OF DIFFERENT DIETARY PROTEIN CONTENT ON ACTIVITIES OF PEPSIN AND AMYLASE OF SILURUS MERIDIONALIS CHEN

In order to research the relationship between the nutrients or feedstuffs and the digestive enzymes in fish,it was studied in this paper that the changes of pepsin or acid protease and amylase activities in pancreas,stomach,foregut and hindgut of Silurus meridionalis were measured at 0d,15d,25d and 50d with different protein content diet,containing protein 44.8%,29.1%and 13.3%and naming high protein content diet(HPCD),intermediate protem content diet(IPCD)and low protein content diet (LPCD) respectively.The results are as follows: 1) Silurus meridionalis in HPCG and IPCD groups (44.8% and 29.1%) grow faster than does in LPCD group;In the anaphase (after 25d),the growth rate of this fish in IPCD group is biggest.It shows that the protein content in pellets is about 29.1% or little more,but not more than 45%. 2) During the former experiment (before 25d),the pepsin or acid protease activities in stomach show the tendency to decrease in all three groups.But in the later experiment(after 25d),the pepsin activity in stomach of S.meridionalis in the IPCD group tends to increase,while that to decrease in other two groups.These show that the protein content in diets can influence the pepsin activities in stomach of the fish.The acid protease activities in pancreas,foregut and hindgut are very low,they had very little action on digesting diet.Combined to the growth of this fish,it shows that there have some correlations between the changes of pepsin activities in stomach and growth after a period time of rearing. 3) In the whole experiment,the amylase activities in pancreas are higher than that in other three organs or tissues in the three groups.And in the earlier experiment(before 15d),the amylase activities in pancreas decreased slowly,but increased rapidly from 15d to 25d.Then this enzyme activity became stable after 25d in the HPCD group,but in other two groups the activities kept to increase. 4) During the whole the amylase activities fluctuated to some extent in all groups,but in the later period(after 25d),the amylase activities in the foregut and hindgut in the LPCD group decrease rapidly,but this enzyme activities still increase in the same time.These also suggest that amylase enzyme activities or their changes correlate to the growth of this species. 5) Over the whole experiment,the characters of the distribution of pepsin or acid protease and amylase activities to all tissues or organs studied are similar in all three groups. It shows that the protein content in diets did not influence the distribution of these two enzyme activities to all tissues or organs. The changes of the two enzyme activities among the three groups in the experiment suggest that how much protein in diets influences the synthesis,secretion and action of pepsin in stomach and amylase of this species.