Phagostimulant MTSG supplementation benefits growth-promoting and defensive effects of Rhodobacter azotoformans on Chinese mitten crab Eriocheir sinensis

The use of phagostimulant and Rhodobacter has been well proposed in Chinese mitten crab Eriocheir sinensis culture. Yet the influence of phagostimulant supplementation on the growth-promoting and defensive effects of Rhodobacter on Chinese mitten crabs is still unknown. In this study, a 40-day feeding trial was carried out to examine the contribution of dietary phagostimulant MTSG to the effects of R. azotoformans on the growth performance, immunity, antioxidant capability, intestinal flora diversity, and resistance of E. sinensis to bacterial challenge. The results revealed higher weight gain, specific growth rate, as well as serum and hepatopancreatic acid phosphatase, alkaline phosphatase, superoxide dismutase, and catalase activities in the 3.0 to 9.0 g/kg diet MTSG + R. azotoformans-fed crabs than R. azotoformans-fed crabs, indicating that the supplementation of MTSG at 3.0 to 9.0 g/kg diet could improve the effect of R. azotoformans on growth performance, immunity and antioxidant capability of Chinese mitten crabs. Furthermore, the supplementation of MTSG at 3.0 to 9.0 g/kg diet could strengthen the effect of R. azotoformans on intestinal flora diversity of Chinese mitten crabs, and enhance the effect of R. azotoformans on the disease resistance against S. putrefaciens infection. To the best of our knowledge, this is the first study to reveal the contribution of a phagostimulant (MTSG) to the growth-promoting and defensive effects of R. azotoformans on Chinese mitten crabs.