Effects of Spirulina platensis as a substitute for fishmeal on the liver of zig-zag eel (Mastacembelus armatus) infected with Aeromonas hydrophila

With the development of economy, there is an increasing demand for higher value fish such as Zig-zag eel (Mastacembelus armatus). However, M. armatus, as a carnivorous fish, needs to be trained to feed during the juvenile period in order to save the culture cost, so as to improve its culture efficiency. However, with the increasing price of fishmeal and the higher amount of harmful bacteria in the water body, the development of M. armatus aquaculture is seriously constrained. Therefore, in this experiment, different proportions of Spirulina platensis (0, 5 %,10 %, 15 %, 20 %, 25 %) were used to replace fishmeal and fed to M. armatus seedlings during the period of dietary transition. Finally, M. armatus was infected with Aeromonas hydrophila to investigate the effect of S. platensis on the immunity of M. armatus. The results showed that S. platensis significantly reduced the damage caused by A. hydrophila to the liver of M. armatus. S. platensis could improve the antioxidant capacity of the organism by increasing the activities of T-SOD, GSH-px and T-AOC, as well as decreasing the activity of MDA. The transcriptome showed that S. platensis could activate the hepatic activation of Glycolysis/Gluconeogenesis and AMPK signaling pathway. In the Glycolysis/Gluconeogenesis pathway, the gpi, pfkl and pfkp genes had the strongest correlation with other genes. Metabolomic results showed that S. platensis activates pathways such as Nicotinate and nicotinamide metabolism and Arginine and proline metabolism. In conclusion, S. platensis can effectively improve the infection tolerance of M. armatus against A. hydrophila. This suggests that S. platensis has great potential in promoting liver metabolism and boosting the body's immunity, which is of great value for application.