Biofloc Technology Improves Keeled Mullet (Liza carinata) Growth, Antioxidants, Immunological Responses, and Expression of Immune-Growth Related Gene

Biofloc technology represents a complex ecosystem of microorganisms intended to enhance the efficiency and sustainability of aquaculture. The present trial was designated to analyze Liza carinata (Keeled mullet) suitability to be cultured in biofloc system. Two treatments were designed including clear water system (CWs) and biofloc technology system (BFTs) in triplicates for each treatment. Keeled mullet fry (weighted 0.49 ± 0.01g)  were assigned randomly to six round plastic tanks (120 liters) of the two treatments at 15 fry/tank. After 90 days, the results revealed that water quality were kept at appropriate levels in both treatments. Fish growth in BFTs was significantly better than CWs. Better proximal body composition with higher protein and lipids percentages were found in fish reared in BFTs. BFTs improved intestinal activities of amylase, lipase and protease. Fish raised in BFTs had a significant improved antioxidant response and lower malondialdehyde than CWs. Fish serum showed higher content of total protein, globulin, albumin, lysozyme, phagocytic activity, respiratory burst activity (NBT) and immunoglobulin M in BFTs than CWs (P<0.05). Reduction of both cortisol and stress enzyme were reported in fish in BFTs than fish in CWs. Higher length and width of villi along with a higher number of goblet cells in addition to higher total bacterial and Bacillus count were recorded in BFTs than CWs. BFTs up-regulated immunity genes, including Tumer Necrosis Factors alpha (TNF-α) Interleukin 1β (IL-1β), Interleukin 8 (IL-8) and Interleukin 10 (IL-10). In addition, higher levels of selected growth genes were recorded in BFTs fish. In conclusion, the present results demonstrated that BFTs maintained water quality and improved growth, fish proximate analysis, activity of digestive enzymes and antioxidants enzymes. BFTs also enhanced hematological, serum-immunological parameters and improved gut health.