Application Of Five Exogenous Enzymes In Diets Of Japanese Seabass (Lateolabrax Japonicus)

This thesis was conducted to investigate the effects of five exogenous enzymes including protease,lipase,xylanase,mixed non-starch polysaccharide enzymes and phytase on growth performance,body composition,serum biochemical parameters,immune and antioxidant indexes,digestive enzymes activities,intestinal structure and aquaculture water quality of juvenile Japanese seabass(Lateolabrax japonicus).The specific contents and main results are as follows:1 Effects of five exogenous enzymes on growth performance,body composition,and serum biochemical parameters of juvenile Japanese seabass(Lateolabrax japonicus).576 Japanese seabass with an initial body weight of 7.47±0.33 g were randomly divided into 6 groups with 4 replicates of 24 fish,and fed with a basal diet and 5 added diets respectively for 56 d.The five added diets were prepared by adding 175 mg/kg protease,65 mg/kg lipase,80 mg/kg xylanase,6 mg/kg mixed non-starch polysaccharide enzymes(2 mg/kg xylanase,cellulase and pectinase respectively)and 300 mg/kg phytase respectively.The six diets were marked as Con,Pro,Lip,Xyl,NSPe and Phy.The results showed that,the growth performance and body indexes in Pro,NSPe and Phy groups had no significant change(P>0.05),except that the hepatosomatic index(HIS)in Phy group was significantly increased(P<0.05).Compared with the control group,the weight gain rate(WGR)and specific growth rate(SGR)in Xyl group increased significantly(P<0.05),while the final mean weight,WGR,SGR and protein efficiency ratio(PER)in Lip group decreased significantly and the feed coefficient(FC)increased significantly(P<0.05).There were no significant differences in whole-body dry matter(DR),crude protein(CP),ether extract(EE)and ash contents(P>0.05)among all groups.There were no significant changes in serum cholesterol(CHOL),low density lipoprotein cholesterol(LDL-CH),triglyceride(TG),high density lipoprotein cholesterol(HDL-CH),urea nitrogen(UN),globulin(GLB),total protein(TP)contents and aspartate transaminase(AST)activity(P>0.05),but alanine transaminase(ALT)activity in Lip group increased significantly(P<0.05).Lactate dehydrogenase(LHD)activity decreased significantly in Pro group but increased significantly in Lip,Xyl and Phy groups(P<0.05).The serum glucose(GLU)content in Lip group decreased significantly(P<0.05)and there was no significant difference among the other groups(P>0.05).The results indicate that the addition of xylanase to diet could improve the growth performance of juvenile L.japonicus,while adding lipase show an opposite effect,and improve serum alanine transaminase activity and decrease glucose significantly.2 Effects of five exogenous enzymes on serum immune and antioxidant indexes of juvenile Japanese seabass(Lateolabrax japonicus).At the end of the above feeding trial,11 L.japonicus were randomly selected from each replicate for collecting blood to analyze immune and antioxidant indexes.The results showed that serum lysozyme(LZM)activity in Xyl group increased significantly(P<0.05)but decreased significantly in Lip and NSPe groups(P<0.05).The addition of exogenous enzymes significantly increased alkaline phosphatase(AKP)activity(P<0.05)in addition to xylanase.Superoxide dismutase(SOD)activity in Pro,Xyl,NSPe and Phy groups were significantly higher than in Con(P<0.05),and the highest value appeared in NSPe(+46.1%)and the second in Phy group(+42.5%).Compared with the Con gruop,the addition of five exogenous enzymes all significantly increased serum total antioxidant capacity(T-AOC)(P<0.05),and the order of value was NSPe>Phy>Pro>Lip>Xyl.Serum malondialdehyde(MDA)content decreased significantly(P<0.05)in Lip group,and no significant differences were found among the other groups.The results indicate that the addition of xylanase to diet could improve lysozyme activity,and the five exogenous enzymes all increase serum total antioxidant capacity of juvenile L.japonicus.3 Effects of five exogenous enzymes on digestive enzymes activities and intestinal structure of juvenile Japanese seabass(Lateolabrax japonicus).After 56-d feeding trail,the stomach,intestine and liver sampled randomly from 3 L.japonicus in each replicate were prepared to determine the activities of protease,amylase and lipase.And the foregut samples were randomly selected from 3 L.japonicus in each replicate to make paraffin slices and the PAS staining.The results showed that compared with the Con group,the pepsin activitiy in NSPe group,the gastric amylase activity in Xyl,NSPe and Phy groups,and the gastric lipase activitiy in Pro and Phy groups increased significantly(P<0.05).The intestinal proteinase activity in added groups,the intestinal amylase activity in Xyl and Phy groups,and the intestinal lipase activity in Pro group were significantly increased(P<0.05),but the intestinal lipase activity in NSPe group was significantly decreased(P<0.05).The hepatic protease activity in added groups,the hepatic amylase activity in Xyl and Phy groups,the hepatic lipase activity in Xyl group increased significantly(P<0.05),but the hepatic lipase activity in Pro,Lip and NSPe groups decreased significantly(P<0.05).Compared with the Con group,the added groups had no significant difference in intestinal muscle thickness,fold height and width(P>0.05).The muscle thickness in Lip group was the lowest(-14.2%),and the fold height in Pro,Lip and Phy groups increased by 14.6%,17.0% and 24.9% respectively.The results indicate that the addition of five exogenous enzymes to diets could improve the activities of protease and amylase in gastrointestinal tract and liver of juvenile L.japonicas,and lipase and phytase increase the fold height to a certain extent.4 Effects of five exogenous enzymes on the nitrogen and total phosphorus contents in aquaculture water of juvenile Japanese seabass(Lateolabrax japonicus).At the end of the feeding trail,10 healthy L.japonicus were chosen from each replicate,and aquaculture water quality was measured during 24 h.The results showed that compared with the Con group,dietary xylanase significantly reduced the ammonia nitrogen content in aquaculture water(P<0.05)and the ammonia nitrogen content reached significant level at 12 h and 24 h,while the addition of other enzymes did not significantly affect the ammonia nitrogen(P>0.05).The total nitrogen content in each group did not change significantly within 24 h.The addition of five exogenous enzymes reduced the total phosphorus content in aquaculture water(P<0.05)in comparison with the Con group,and decreased by 16.7%,16.7%,13.9%,19.4% and 19.4% respectively at 24 h for Pro,Lip,Xyl,NSPe and Phy group respectively.The results indicate that the addition of five exogenous enzymes to diets could reduce nitrogen and phosphorus contents in aquaculture water of juvenile juvenile Japanese seabass and improve the environment of aquaculture water.