Biofloc technology (BFT) has been presented as a sustainable shrimp farming approach capable of decreasing environmental impacts and limiting disease introduction. Bioflocs’ microbial population can boost feed consumption and animal growth as well as eliminate nutrients. The cell walls of bacteria in Biofloc systems are made up of bacterial lipopolysaccharide, peptidoglycan, and B-1,3 glucan, among other components. Non-specific immune response in crustaceans, such as shrimp, is stimulated by bacterial cell wall components. As a result, bioflocs are thought to improve the immune system of shrimp that consume them as a food source. In this study, w e investigated how different carbon sources (sugarcane bagasse, rice straw, and wheat bran) altered the expression of immune-related and antioxidant genes in L. vannamei larvae raised for 90 days. The gene expression of immune-related genes and antioxidant genes was considerably up-regulated with different carbon sources after 90 days of rearing as compared to a control group fed a basic diet. Immune-related genes (Proph, LGBP, and Trans) had higher gene expression in all biofloc treatments, with the highest expression in the sugarcane bagasse (SCB) group . The expression of antioxidant genes (SOD, GPx) increased significantly in the biofloc groups, with SOD expression increasing by (4.5-, 3.2-, and 2.5-fold changes) in SCB, wheat bran, and rice straw, respectively. In addition, the SCB group had the greatest GPx expression. Biofloc not only improves shrimp immunity, but it also improves growth, since all biofloc groups grew faster than the control group. To sum up , this study found that adding different carbon sources (sugarcane bagasse, rice straw, and wheat bran) as a direct feed to L. vannamei for 90 days improved shrimp immunity, growth, and reduced stress, as evidenced by underline molecular changes in expression of immune-related and antioxidant genes, and we strongly recommend the use of biofloc technology, particularly sugarcane bagasse, as a cost-effective and feasible source of carbon in shrimp farming.
Acknowledgements: The research was performed within the “Development and Research Application of biofloc Technology for increasing shrimp production in Egypt (EGY-DRAFT)” project, which is financially supported, by the Science & Technology Development Fund (STDF), Ministry of Scientific Research, Egypt. (Agreement No. 25305, Reintegration Grants). The authors are grateful for all the support.