| In this study, we investigated the effects of antimicrobial peptide C(AMPC)and P(AMPP) on the performance, Whole-body composition, non-specific immunity,antioxidant activity, digestive enzyme activity, intestinal morphology and immune-related gene expression in GIFT(Oreochromis niloticus). It contained six groups including one control group(G1) and five experimental groups in this study. The AMPC and AMPP were added into basal feeds(Control) as additives at five concentrations: 200mg/kg of AMPC in all experimental groups and 25mg/kg(G2), 100mg/kg(G3), 400mg/kg(G4), 800mg/kg(G5)and 1600mg/kg(G6) of AMPP. After 56-day feeding Trial, the samples were colleted and the indices were determined, then the results were showed as follows:1. The diets of complex AMPC and AMPP inhibited the growth of GIFT, and the G4 and G6 diets had decreased the growth performance evidently. The final weight, specific growth rate(SGR), weight gain rate(WGR) of fish in G2 、 G3 、 G4 、 G5 and G6 were significantly lower than the control(p<0.05), and the feed coefficient(FCR) was significantly higher than the control(p<0.05). The AMPs-supplemented diets could increase the contents of crude protein of whole fish, however, all proximate compositions of the whole-body of GIFT had not significant difference between the AMPs-treated groups and the control(p>0.05).2. The serum total protein(TP), albumin(ALB), globulin(GLO) contents were increased in the groups of AMP supplementation, and the G4、G5 and G6 were significantly higher than the control(p<0.05).3. The diets added AMPs improved antioxidant activity and non-specific immunity of GIFT. It showed that the activities of total antioxidant capacity(T-AOC), superoxide dismutase(SOD), catalase(CAT) and lysozyme(LZM) were higher than the control, and the levels of malondialdehyde(MDA) and lipopolysaccharide(LPS) were significantly lower compared with the control(p<0.05). The activities of T-AOC in G4 and LZM in G5 were significantly influenced(p<0.05).4. The AMPs-treated diets decreased the activities of trypsin, pepsin and lipase of hepatopancreas. Among all test groups, the three of G4 and G6 groups were significantly decreased(p<0.05). The pepsin and lipase had the lowest activities in the G6 group. There was no significant difference of amylase activity among all groups(p<0.05).5. The AMP additives damaged the intestinal structures of GIFT in some extent,especially the proximal part. The result showed that the V/C values of the proximal, middle and distal parts in all AMPs-groups were lower than the control, and the proximal part had significant differences compared to the control(p<0.05).6. The AMPs-diets enhanced immune-related gene expression in hepatopancreas,spleen, kidney and gill. The G6 group exihibited significant higher m RNA expression levels of TNF-α, IL-1β, IFN-γ and HSP70 in hepatopancreas, spleen(except IL-1β) and kidney compared with the control(p<0.05). TNF-α, IL-1β and HSP70 in G4 hepatopancreas had significant relative expression levels than the control(p<0.05). The diet of 200mg/kg of AMPC with 100mg/kg of AMPP showed significant enhancement of IFN-γand HSP70 expressions in kidney and IL-1β expression in gill. Generally, the expressions of immune-related genes had fluctuant enhancement, which depended on the AMPP concentration over 100mg/kg, and the concentration of 1600mg/kg exhibited evident increase.Results of the study indicated that the concentrations of AMPC and AMPP combined decresed the growth performances, the activities of degistive enzymes, damaged intestinal structures whereas improved antioxidant activity, non-specific immunity, and enhanced immune-related gene expression of GIFT. |
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