Assessing Feasibility Of Replacement Of Fishmeal Protein With Enzyme-treated Feather Meal In The Diet Of Juvenile Turbot(Scophthalmus Maximus L.)

Enzyme-treated feather powder is a new animal protein material,but it is seldom used in aquatic animal feed.To comprehensively evaluate the effect of enzymehydrolyzed feather powder(EFM)instead of fishmeal(FM)protein in the feed of turbot(Scophthalmus maximus L.)EFM was prepared by enzymatic hydrolysis of steamprocessed feather meal(SFM)in vitro with keratinase(PH: 7.5,reaction temperature: 50 ?)to study the effects of feather powder on the growth,feed utilization,body composition and nutrient metabolism of turbot,so as to determine the potential of enzymatic feather powder to replace fish meal.A feeding trial was conducted to examine the potential of enzyme-treated feather meal(EFM)as a fishmeal substitute in the diet of turbot.Fishmeal was incrementally replaced(0,16,32,48,64,80%)by EFM(0,8%,16%,24%,32%,40%)to produce six experimental diets.The seventh diet(EFM24+AA)was supplemented with lysine and methionine.Another diet was formulated with SFM to replace 48% fishmeal.Eight diets were each fed to triplicate groups of juvenile turbot(initial weight: 37.47g)in a recirculating aquaculture system for 7 weeks.The results showed that 1)EFM did not affect the SR,amylase and trypsin activity of juvenile turbot(P>0.05);2)The addition of 8% EFM had no effect on the Final body weight(FBW),weight gain(WG),feed efficiency(FE),daily feed intake(DFI),protein efficiency ratio(PER),apparent digestibility(ADC)of dry matter,fat,energy,amino acid of juvenile turbot(P>0.05),significantly reduced protein digestibility and lipase activity(P<0.05);3)Adding 24% EFM had no significant effect on the organ indices,of juvenile turbot(P>0.05);4)Adding 32% EFM significantly improved muscle water content(P<0.05);5)Fish fed SFM24 significant reduced growth performance and feed utilization,body Tyr content,muscle fat content,lipase activity and digestibility of body protein,Val,Leu,Phe,His,Arg,Ser,Glu,Ala,Gly,Cys,Pro than EFM24(P<0.05);6)The growth performance,feed utilization,condition factor,body protein content,muscle protein content,dry matter,protein,fat,lysine(Lys)and methionine(Met)digestibility,lipase and pepsin activity of juvenile turbot in EFM24+AA group were significantly higher than those in EFM24 group(P<0.05).The study showed that dietary with 8% EFM had no effect on the growth performance and digestibility of nutrients of turbot.Supplementation with lysine and methionine could significantly improve the growth performance and feed utilization of turbot.The surem and livers required for the determination of indicators were all taken from the juvenile turbot in the feeding trial,to investigated the Influence of enzyme-hydrolyzed feather meal replacement of fish meal protein on serum biochemical index,liver antioxidant indexes,nutrient metabolism and blood free amino acids of juvenile turbot.The results showed that 1)EFM did not affect the blood glucose,activity of blood GOT,GPT and the relative expression level of GK and PEPCK gene(P>0.05).2)With the addition of EFM,the relative expression of fructose-1,6-diphosphatase(FBP)and glucose-6-phosphatase(G6Pase)genes increased first and then decreased(P<0.05);3)When dietary EFM level reached 8%,the liver GOT activity and pyruvate kinase(PK)gene expression levels were significantly reduced(P<0.05);4)When EFM level up to 16% significantly reduced liver GPT activity,blood LDL-C,HDL-C,T-CHO,TP content,and liver GPT activity(P<0.05);5)When the dietary EFM level increased to 24%,the activity of catalase(CAT)was significantly decreased,and the content of malondialdehyde(MDA)in the liver was significantly increased(P<0.05);6)When dietary EFM level reached 32%,blood TP content and total superoxide dismutase(TSOD)activity in liver were significantly reduced(P<0.05);7)When the dietary EFM level increased to 40%,significantly reduced blood Alb content(P<0.05);8)There were no significant difference with serum biochemical index between EFM24+AA and EFM24(P>0.05),but significantly improved liver GOT activity(P<0.05);9)SFM24 had significantly reduced blood TP content,liver GOP and GPT activity(P<0.05);10)The plasma free amino acids of the control group and EFM24 group peaked at 2h and SFM24 group peaked at 8h.The results showed that dietary EFM did not cause liver damage to turbot.When the dietary EFM level more than 8%,the transaminase activity and the content of lipids and proteins in blood were significantly reduced.The peak time of total free amino acids in EFM24 group was earlier than that in SFM24 group.To investigate the effects of enzyme-hydrolyzed feather meal and steam-processed feather meal replacing fish meal protein on intestinal microbial community structure of juvenile turbot,FM(C)group,EFM24(F)group and SFM24(P)group were selected as the treatment group of this experiment,the results showed that 1)the total effective sequence of 12 samples in the three groups was 372,939,the number of operational taxonomic units(OTU)in groups C,F and P were 982,859 and 1059,respectively,the common OTU numbers of group C and group F,group C and group P,and group F and group P were 351,413 and 247,respectively;2)According to the bacterial annotation results,the dominant phyla of juvenile turbot were Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes;3)According to the species abundance heat map,the first three phyla with high abundance were the same as group C and group F,but quite different from group P;Among the top 50 OTU with the highest abundance in the samples,no common pathogenic bacteria were found in turbot.To sum up,diet with 24% EFM did not affect the composition of intestinal microflora of juvenile turbot,but diet with 24% SFM would change the composition of intestinal microflora of fish and increase the bacterial abundance.The addition of two kinds of feather meal would not increase the bacterial abundance of intestinal microflora of juvenile turbot.