Growth performance, hepatic enzymes, and gut health status of common carp (Cyprinus carpio) in response to dietary Cetobacterium somerae fermentation product

Intensive aquaculture practices compromise the health of fish. Probiotics especially those isolated from aquatic animals play important roles in improving fish health. The aim of the study was to evaluate the effects of stabilized fermentation product of Cetobacterium somerae (XMX-1) on the growth performance, gut and liver health of common carp. A total of 300 carps (initial weight of 2.32 +/- 0.02 g) were divided into the control (fed a basal diet) and XMX-1 groups (fed a basal diet with 2 g/kg, 3 g/kg, 4 g/kg or 5 g/kg XMX-1 diet). After 8-week feeding, growth performance, serum lipopolysaccharide (LPS), diamine oxidase activity (DAO), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were evaluated. The intestinal total superoxide dismutase (SOD) activity, the expression of gut health related genes was tested. In addition, the liver triacylglycerol (TAG) and the expression of liver lipid metabolism related genes were conducted. Results showed that XMX-1 addition had no effect on the growth performance of carps at a supplementation level up to 5 g/kg (P 0.05). However, dietary XMX-1 at addition levels ranging from 2 g/kg to 5 g/kg reduced serum LPS and DAO. Furthermore, all XMX-1 additions significantly increased total SOD activity compared with the control group (P < 0.05). In contrast, dietary 3 g/kg XMX-1 significantly increased the expression of intestinal hypoxia inducible factor 1 subunit alpha (HIF1 alpha), Occludin, Hepcidin and zonula occludens (ZO)-1 (P < 0.05). Dietary 2 g/kg XMX-1 significantly increased the expression of intestinal Hepcidin and ZO-1 (P < 0.05). Moreover, dietary XMX-1 decreased the level of serum ALT (P < 0.37) and liver TAG (P < 0.07). Furthermore, we found that dietary XMX-1 significantly reduced the expression of genes related to lipid synthesis including sterol regulatory element-binding protein (SREBP1c) and peroxisome proliferator-activated receptor gamma (PPAR gamma) (P < 0.05). Meanwhile, dietary 3 g/kg XMX-1 significantly increased the expression of carnitine palmitoyltransferase 1 (CPT1) and peroxisome proliferatoractivated receptor alpha (PPAR alpha) compared with the control group (P < 0.05). Together, our findings suggest that XMX-1 additions of 3 g/kg had the best effect on fish health.