Effects Of Dietary Chitosan-oligosaccharide On Growth Performance, Immune Function And Antioxidant Parameters Of Ffrc Strain Common Carp

This study was conducted to investigate the antibacterial effects of dietary chitosan-oligosaccharide (COS) and its effects on growth performance, immune parameters and antioxidant parameters of FFRC Strain Common Carp(Cyprinus carpio), in order to providing theoretical basis for the application of COS in aquaculture.In vitro antimicrobial effects of COS were investigated in experiment1. Two different methods, paper disk method and turbidimetry, were used for analysis of inhibition zone diameters and minimal inhibitory concentration (MIC) against three bacteria (Escherichia coli, Aeromonas hydrophila and Vibrio fluvialis). The results indicated that COS had inhibitory effect against three bacteria, whic was enhanced with increasing concentration. The MICs of COS on three bacteria was determined as100,800and800mg/L.Experiment2was aimed to evaluate the effects of dietary COS levels on growth performance, biometric parameters, muscle composition, plasma biochemical parameters, intestinal microflora and morphological parameters of FFRC Strain Common Carp(Cyprinus carpio). A single factor design was adopted, and the fish (mean initial weight of33.83±0.11g) were randomly divided into4groups with5replicates per group and15fish per replicate. The fish were fed a basal diet (control group) and the same diet supplemented with COS at25,50or100mg/kg respectively for35d. The results showed that dietary supplementation of COS did not significantly affect the growth performance, biometric parameters, muscle composition or plasma biochemical parameters of fish compared with the control group (P>0.05). Dietary supplementation of COS at100mg/kg decreased18-d plasma T3concentration, but increased35-d plasma T4concentration (P<0.05). COS had no significant effect on the intestinal microflora of fish (P>0.05). In addition, dietary supplementation of COS at50mg/kg significantly increased the height of intestinal folds(P<0.05). Experiment3was aimed to study the effect of dietary COS levels on immune parameters and antioxidant parameters of FFRC Strain Common Carp (Cyprinus carpio). The experimental design was the same as in Experiment2. The results indicated that dietary supplementation of COS significantly elevated the activity of plasma alkaline phosphatase (AKP)(P<0.05), but did not affect the levels of plasma complement3(C3), complement4(C4), IgM-like, or total iron binding capacity (TIBC)(P>0.05); Intestinal mucous cells in fish fed COS at50and100mg/kg were more than those in the control group (P<0.05); Increased18-d superoxide dismutase (SOD) activity and35-d myeloperoxidase (MPO) activity in spleen as well as decreased plasma maleic dialdehyde (MDA) level at both18and35d were observed in fish fed COS at50and100mg/kg, which also had elevated SOD activity in plasma and hepatopancreas, respectively. Moreover,18-d AKP activity and35-d nitric oxide (NO) level in spleen were promoted in fish fed COS at50and25mg/kg, respectively.In conclusion, based on the above results, dietary supplementation of50mg/kg exerted the best effects on FFRC Strain Common Carp in the present study.