A compound of paraprobiotic and postbiotic derived from autochthonous microorganisms improved growth performance, epidermal mucus, liver and gut health and gut microbiota of common carp (Cyprinus carpio).

High-density intensive farming is the development trend of modern aquaculture, which is characterized by high density culture environment and feeding of high-fat diet. The use of high-fat diet can increase the weight gain rate of some fish species, but it affects the health of fish. In this study, we investigated the beneficial effects of a compound of paraprobiotic and postbiotic (CPP) derived from autochthonous microorganisms supplemented diet on growth performance, epidermal mucus, liver and gut health, and gut microbiota profile of common carp (Cyprinus carpio). Common carp were fed with diets supplemented with 0, 1, 2 or 3 g/kg of CPP in the control diet for 14 weeks, with four replications in each group and 20 fish in each repetition. The results showed that fish fed with diet supplemented with CPP significantly decreased the hepatosomatic index (p < 0.05), even though no significant effects were observed in the growth performance of the fish. In the CPP1.0 and CPP2.0 groups the level of complement 4 and superoxide dismutase (SOD) activity in the epidermal mucus were significantly increased compared to the control group (p < 0.05). No significant values were recorded among the treatment groups in the level of Lysozyme activity and total antioxidant capacity (T-AOC) (p > 0.05). For liver health, dietary CPP2.0 were significantly decreased the Triacylglycerol content in the liver, compared with the control (p < 0.05). Furthermore, fish groups fed with CPP1.0 and CPP2.0 showed significant decreased in the number of vacuoles representing lipid droplets and the liver damage scores (p < 0.05), compared with the control group. The CPP2.0 group significantly decreased serum alanine aminotransferase (Alt) and aspartate aminotransferase (Ast) levels, and significantly increased liver antioxidant (total antioxidant capacity, superoxide dismutase and catalase (CAT)) levels compared to the control group (p < 0.05). The level of liver malondialdehyde (MDA) was significantly reduced in the CPP groups compared to the control (p < 0.05). Dietary CPP supplementation were significantly down-regulated the relative expression of pro-inflammatory cytokines (nf-κb p65 and tnf-α) and up-regulated anti-inflammatory cytokines (il-1β, il-10 and tgf-β), compared to the control group (p < 0.05). Similarly, intestinal hypoxia inducible factor 1 subunit alpha (hif-1α) expression was significantly increased in the CPP1.0 and 2.0 groups, compared with then control (p < 0.05). Combined with intestinal HE staining and inflammatory gene expression, it was found that the intestinal inflammatory cytokines (nf-κb p65 , il-1β, il-10 and tgf-β) in the CPP2.0 supplemented group were significantly higher than the control group (p < 0.05), and the intestinal villi were more orderly arranged. In the CPP3.0 group, the expression of nf-κb p65 , il-1β, il-10 were significantly higher compared with the control (p < 0.05). Furthermore, remarkably lower intestinal injury scores were recorded in the CPP groups verses the control (p < 0.05). The gut microbiota diversity index data showed that lower diversity index values were observed in the CPP2.0 group compared with the control (p < 0.05). The relative abundances of Fusobacteria and Cetobacterium in the CPP2.0 and 3.0 groups were significantly higher than those in the control group (p < 0.05). In conclusion, dietary CPP supplementation could enhance non-specific immunity and antioxidant levels, reduce liver lipid deposition, alleviate liver and intestinal damage and inflammation, and improve gut microbiota abundance and diversity in common carp fed with high-fat diet. The best positive effect was observed in common carp fed with diet supplemented at a level of 2 g/kg of basal diet. • The compound of paraprobiotic and postbiotic (CPP) ensured growth and reduced hepatosomatic index of common carp. • CPP2.0 group improved non-specific immunity and antioxidant levels of common carp. • CPP2.0 group effectively improved liver and intestinal health of common carp. • CPP2.0 group significantly enriched the relative abundances of Fusobacteria and Cetobacterium in gut. [ABSTRACT FROM AUTHOR]