Effects of dietary Humulus scandens extract on growth performance, antioxidant responses and intestinal microflora of Yellow River carp (Cyprinus carpio)

In the present study, the effects of Humulus scandens extract on growth performance, antioxidant responses and intestinal microflora of Yellow River carp (Cyprinus carpio) were investigated. 240 carps were assigned to four treatments received diets supplemented with 0 (control), 0.5, 1 and 2 g/kg Humulus scandens extract for 8 weeks. At end of the trial, the final body weight, specific growth rate (SGR) and intestinal body index of the 1.0 g/kg and 2.0 g/kg group were significantly higher than those of the control group (P < 0.05). No significantly differences were observed for food conversation ratio (FCR) or protein efficacy ratio (PER). The SOD (superoxide dismutase) content in gills of the treatment groups was significantly increased compared to the control group (P < 0.05), GPX (glutathione peroxidase) content in gills of 2.0 g/kg group was significantly higher than that of other groups (P < 0.05). Compared with the control group, the contents of SOD, CAT (catalase) and GPX in the liver of the treatment groups were significantly higher (P < 0.05). The gene expression levels of SOD, CAT and GPX in gill and liver of 1.0 g/kg and 2.0 g/kg group were significantly higher than those of control group (P < 0.05), and the gene expression level of HSP70 in gill and liver was decreased compared to the control group. The trypsin activity, fold height, crypt depth and goblet cell number in 1.0 g/kg and 2.0 g/kg group were significantly higher than those in control group and 0.5 g/kg group (P < 0.05). At the phyla level, the abundance of Actinobacteria in 0.5 g/kg group, Verrucomicrobia in 1.0 g/kg group and Fusobacteria in 2.0 g/kg group were significantly increased compare to the control group. At the genus level, compared with the control group, the abundances of Luteolibacter in 1.0 g/kg group, Gemmobacter and Cetobacterium in 0.5 g/kg and 2.0 g/kg groups were significantly higher. In conclusion, the present study demonstrated that 1.0 g/kg-2.0 g/kg level Humulus scandens extract is beneficial to growth performance, antioxidant activity and intestinal health of Yellow River carp.