Partial replacement of pelleted feed by moist fermented feed improved the feed conversion efficiency, liver and intestine health, and gut microbiota structure in common carp (Cyprinus carpio)

This study aimed to explore whether the substitution of basic pellet feed by different proportions of moist fermented pellet feed affect the growth performance, liver and gut health, and intestinal microbiota structure of common carp (Cyprinus carpio). The experiment was divided into 5 groups: the control group was fed with the basic pellet feed, and the treatment groups were fed with the feed that moist fermented pelleted feed (MFF) substituted 5% (MFF5), 10% (MFF10), 15% (MFF15) and 20% (MFF20) of the basic pellet feed. Feeding trial was lasted 8 weeks. The results showed that the feed efficiency of MFF10 groups was significantly higher than that of control group. MFF replacement had no significant effect on the weight again and survival rate of C. carpio compared with Control. In addition, MFF substitution showed that the liver anti-inflammatory factors TGF-β in MFF groups except MFF5 group showed a significant upward trend, liver IL-10 of MFF15 and MFF20 groups and intestinal TNF-α of MFF10 were significantly higher than those of control group. Moreover, the intestinal zo-1 of MFF5 and MFF10 groups, hepcidin of MFF5, and defensin in MFF5 and MFF10 were significantly elevated compared with the control (P < 0.05). We also found that the abundance of Fusobacteria in the MFF10 group and Firmicutes in MFF15 increased significantly compared with the control (P < 0.05), while the abundance of Bacteroidota in MFF10 was remarkably lower than that of MFF5 and MFF15 groups (P < 0.05). Meanwhile, Chao1 and Shannon indexes in MFF15 and Ace index in MFF20 were significantly higher than those of the control (P < 0.05). These result suggested that replacement of basic pellet feed with a range of 5–15% of fermented feed could be considered as an important way to improve the health and production of common carp.