The Study On Replacement Of Fish Meal With Enzymatic Hydrolysates Of Silkworm Pupa In Feed For Mirror Carp(Cyprinus Carpio Var.Specularis)

Fish meal(FM)has the characteristics of high protein content,nutrient-rich and good palatability.It is the main protein source in the aquaculture industry.But with the storage of resources and climate variation,the production of FM declined year by year,and the sustainable development of the aquaculture industry faced severe challenges.Therefore,in recent years the study of partial or total replacement of FM by the high quality protein of animal and plant protein source has become the hot point in aquatic feed industry.Silkworm pupa is riched in protein and lipid content.It is a high quality insect protein source.The high weight protein conposition of delipidted silkworm pupa meal can be decomposed into small ones by enzyme.It is good for the absorption of fish.This study will make efforts on the following aspects: Effect of replacement of dietary FM with enzymatic hydrolysates of delipidted silkworm pupa meal(EDSP)on growth performance,biological character,body composition,serum biochemical indicators,antioxidant ability and intestinal digestive enzyme activities in juvenile mirror carp(Cyprinus carpio var.specularis),(mirror carp,for short).It is aimed to explore the feasibility of EDSP as a new protein source in juvenile mirror carp diets and determine the appropriate add level.Finally it could provide reference for the development and utilization of aquatic animal protein source.The research has two parts,for one part,The EDSP was prepared by using the multienzyme compound of Alcalase,Flavourzyme,Trypsin and Neutrase with equal ratios hydrolyzing delipidted silkworm pupa(DSP).Using the method of SDS-PAGE to analyze the degree of protein degradation.For another part,using EDSP to substitude FM with 0%,25%,50%,75%,100%.The five diets were isonitrogenous and isolipidic.The experimental fish of 270 with same size(initial average weight,14.51 ± 0.03 g)were randomly raised in the circulating water system.They were fed in 15 tanks for 8 weeks.At the end of the feeding trial,all of the fish were fasted for 24 h and anesthetized with MS-222(100 mg L-1).The growth performance,biological character,body composition,serum biochemical indicators,antioxidant ability and intestinal digestive enzyme activities were measured and analyzed.Then observing the liver and intestinal morphological structure.The experiment results showed as follow:(1)The protein components of the EDSP have relatively small molecular sizes compared with the DSP.The degree of hydrolysis(DH)was 50.83%,and the yield of peptide was 61.30%.Silkworm pupa stink disappeared.(2)The final body weight(FBW)and special growth rate(SGR)of fish in EDSP25,EDSP50 groups were no significant differences with EDSP0(P>0.05),but they were significantly higher than EDSP75 and EDSP100(P<0.05).Weight gain rate(WGR)in EDSP100 was significantly lower than EDSP0(P<0.05);Feed conversion ratio(FCR)in EDSP75,EDSP100 were significantly higher than EDSP0(P<0.05).The protein efficiency ratio(PER)in EDSP25,EDSP50 groups were no significant differences with EDSP0(P>0.05),then in EDSP75,EDSP100 groups were significantly lower than EDSP0(P<0.05).(3)The spleen indexes(SI)in EDSP25 was significantly higher than EDSP0(P<0.05).(4)The crude protein of muscle in EDSP25 and EDSP50 were significantly higher than EDSP0(P<0.05).The crude lipid and crude ash of muscle were no significant differences with the EDSP0 groups(P>0.05).The crude protein,crude lipid and crude ash of whole body showed no differences in all groups(P>0.05).(5)Among all serum biological indices,the level of AST,TP,ALB,TG were no differences in all groups(P>0.05).ALT of EDSP25,EDSP50,EDSP75 have differences with EDSP0(P<0.05).GLU in EDSP75 was significantly higher than EDSP0(P<0.05).T-chol in EDSP25,EDSP50,EDSP75 were significantly higher than EDSP0(P<0.05).(6)The serum SOD in EDSP25,EDSP50 were significantly higher than EDSP0(P<0.05)with the tendency of rising.CAT had the same result.(7)Intestinal protease activity increased at first,and the activity of EDSP25 was significantly higher than EDSP0(P<0.05).The Lipase and Amylase activities were no significant differences in all groups(P>0.05).(8)The shape of intestinal villi in EDSP50 group were tidy and the villus height was significantly higher than EDSP0(P>0.05).The nucleus was located in the cytoplasm.The liver cells were complete and lipid droplets were normal.Conclusion: This study demonstrated that the replacement of fish meal could be as high as 50% in juvenile mirror carp diets.While if adding too more,it will inhibit the growth and health of fish.