Carbon sources improve water quality, microbial community, immune-related and antioxidant genes expression and survival of challenged Litopenaeus vannamei Postlarvae in biofloc system

The influence of different processed agriculture wastes as carbon sources including sugarcane bagasse (SCB), rice bran (RB) and rice straw (RS) on water quality, microbial community, and expression of immune-related and antioxidant genes in both hepatic and muscle tissues was evaluated. Furthermore, the cumulative mortality rates of Litopenaeus vannamei when challenged with Vibrio and Shewanella algae were estimated. The experiment lasted for 3 months in outdoor culture ponds, and the results indicated that the water quality parameters improved with different biofloc (BF) treatments. The total heterotrophic bacteria were increased in the BF treatments until the end of the experiment when compared to the control group. Regarding the hepatic and muscular expression of immune-related genes such as beta-glucan-binding protein, lipopolysaccharides/b-glucan-binding protein, prophenoloxidase, lysozyme, crustin, transglutaminase, hemocyanin and antioxidant genes including glutathione peroxidase and superoxide dismutase, the SCB treatment was higher in all genes expression among different BF treatments and control. Moreover, the SCB treatment also had the best survival rate compared with RB, RS and control treatments when challenged with both Vibrio and Shewanella algae. In general, these results suggested that the SCB is an ideal carbon-rich food source, boosts the immune system and promotes disease resistance of L. vannamei.