Effects Of Chitosan Oligosaccharide,Mannan Oligosaccharides And Alginate Oligosaccharides On The Growth And Immunity Of Cherax Quadricarinatus

The green and healthy aquaculture model has become a trend,and seeking feed additive that can replace antibiotics is an important task nowadays.Functional oligosaccharides have the advantages of being diverse,abundant sources,trace and efficient,and non-toxic,harmless and residue-free,which are important substances to replace antibiotics.In this experiment,three kinds of functional oligosaccharides,Chitosan Oligosaccharide(COS),Mannan Oligosaccharides(MOS)and Alginate Oligosaccharides(AOS),were selected to be added to the feed of an emerging freshwater crayfish species,Crayfish.The functional oligosaccharides were added to the feed to investigate their effects on the Cherax quadricarinatus.The main findings of the study were as follows:The results of COS showed that the final weight,weight gain and specific growth rate were significantly higher in group C2 than in group C0,and the survival rate was significantly higher in group C3 than in group C0.COS had no significant effect on the content of moisture,crude fat and crude ash in the muscle of C.quadricarinatus,and significantly increased the content of crude protein in the muscle.COS significantly increased alkaline phosphatase(AKP)activity,acid phosphatase(ACP)activity,total antioxidant capacity(T-AOC),superoxide dismutase(SOD)activity,catalase(CAT)activity,glutathione peroxidase(GSH-Px)activity in plasma and hepatopancreas of C.elegans,and significantly reduced plasma and hepatopancreas malondialdehyde(MDA)content.The relative expression of GSH-Px,SOD,thioredoxin(Trx),lysozyme(LZM)and anti-lipopolysaccharide factor(ALF)genes in the hepatopancreas of C.aeruginosa was significantly increased.The survival rate of the C2 group was 33.33%higher than that of the C0 group in the Aeromonas hydrophila attack assay.COS was able to improve the Alpha diversity and Bate diversity of the gut microorganisms of C.quadricarinatus.The results of this experiment showed that the dominant gut microbial phyla of C.quadricarinatus were Proteobacteria,Firmicutes,Fusobacteriota and Bacteroidota.COS reduced the abundance of Vibrio in the gut of crayfish.The results of MOS showed that the final body weight,weight gain rate and specific growth rate of M3 group were significantly higher than those of M0 group,and the survival rate of each experimental group was higher than that of M0 group.MOS had no significant effect on the content of moisture,crude protein and crude ash in the muscle of C.quadricarinatus,and significantly reduced the content of crude fat in the muscle.MOS significantly increased AKP activity,ACP activity,T-AOC,SOD activity,CAT activity,GSH-Px activity,and significantly decreased plasma and hepatopancreas MDA content.The expression of GSH-Px,SOD,Trx,LZM and ALF functional genes in the hepatopancreas of crayfish was significantly increased.In the Aeromonas hydrophila attack test,the survival rate of the M4 group was increased by 37.78%compared to the M0 group.MOS was able to improve the Alpha diversity and Bate diversity of the gut microorganisms of C.quadricarinatus.The results of this experiment showed that the dominant gut microbial phyla of C.quadricarinatus were Proteobacteria,Firmicutes,Bacteroidota and Fusobacteriota.MOS was able to increase the abundance of Candidatus Hepatoplasma in the gut of C.quadricarinatus.The results of AOS showed that the final body weight was significantly higher in groups A1,A2,A3 and A4 than in group A0,and the weight gain rate and specific growth rate were significantly higher in groups A2,A3 and A4 than in group A0.AOS had no significant effect on water and crude protein content in the muscles of crayfish,but significantly reduced crude fat and crude ash content in the muscles.MOS could significantly increase AKP activity,ACP activity,T-AOC,SOD activity,CAT activity and GSH-Px activity in plasma and hepatopancreas,and significantly reduce MDA content in plasma and hepatopancreas.The expression of GSH-Px,SOD,Trx,LZM and ALF functional genes in the hepatopancreas of C.elegans was significantly increased.The survival rate of the A3 group was 35.55%higher than that of the A0 group in the Aeromonas hydrophila attack test.AOS was able to improve the Alpha diversity and Bate diversity of gut microorganisms in C.quadricarinatus.The results of this experiment showed that the dominant phyla in the intestinal tract of crayfish were Proteobacteria,Firmicutes,Bacteroidota and Fusobacteriota,and AOS reduced the abundance of Candidatus_Bacilloplasma in the intestinal tract of crayfish.The addition of functional oligosaccharides to the feed had a significant effect on the growth performance,muscle composition,immunity,disease resistance and intestinal microorganisms of C.quadricarinatus,etc.Considering all indicators and production costs it is recommended that the appropriate range of addition of COS to C.quadricarinatus feed is 400～600 mg/kg,MOS is 400～600 mg/kg and AOS is 600～800 mg/kg.COS,MOS and AOS can be developed as new feed substitution additives for aquatic animals.