Effects of dietary protein levels on the activities of digestive enzymes and the muscle compositon of juvenile red swamp crayfish Procambarus clarkii Girard

The juvenile of red swamp crayfish(5.46 g±0.51 g)were fed for 28 days with four protein concentration diets(30%,35%,40%,45%),which were equal in energy,then the effects of dietary protein levels on the activities of digestive enzymes and muscle composition of juvenile red swamp crayfish were analyzed.The results showed that the lipase and protease activities in the intestine and hepatopancreas were significantly influenced by dietary protein level(P0.05);With the increase of the dietary protein level,the lipase and protease activities in the intestine and hepatopancreas increased firstly and then dropped.The protease activities in the intestine and hepatopancreas were the highest when the dietary protein level were 40% and 35% respectively;The lipase activities in the intestine and hepatopancreas were both the highest when the dietary protein level was 40%,but there was no significant difference between 35% and 40%(P0.05).The amylase activity changes in the intestine and hepatopancreas of the juvenlie red swap crayfish both were of wave types with the dietary protein level increasing;The amylase activity in the intestine was significant difference among every treatment except 35% and 45% groups(P0.05);The amylase activity in hepatopancreas was significant difference among every treatment except 30% and 45% groups(P0.05).The protein contents in musle of juvenile red swamp crayfish was higher with the dietary protein level increasing,but there was no significant difference among every treatment except the groups of 30% and 45%(P0.05);The fat contents in muscle of red swamp crayfish was dropped with the dietary protein level increasing,and there were significant difference among every treatment(P0.05).The result showed that there no significant difference between the ash content in the muscle and the dietary protein level.