LAUSR

A 60-day indoor experiment was conducted to study the effect of dietary supplementation of biofloc on metabolic enzyme activities and immune responses in Penaeus monodon juveniles. Biofloc developed in indoor fibreglass-reinforced plastic (FRP) tanks (1000 L) was used as dietary supplement in P. monodon (2.90 ± 0.10 g) reared in 1000-L FRP tanks. Graded level of dried biofloc was included in shrimp basal diets, 0% (control, B0), 4% (B4), 8% (B8) and 12% (B12). The level of metabolic enzymes like malate dehydrogenase (MDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was not significantly different with control up to 8% dietary supplementation. A higher level of total haemocyte count (THC) was noticed in B8 (22.16 ± 2.17 × 106 cells mL−1) and B4 (21.11 ± 0.56 × 106 cells mL−1) compared with control, C (14.61 ± 2.74 × 106 cells mL−1). Biofloc-supplemented groups recorded significantly higher (P < 0.05) serum SOD and catalase activity (P < 0.01) in comparison with control. The groups fed with 4% dietary biofloc supplement recorded highest relative percentage survival (RPS), 45% after challenge with Vibrio harveyi followed by 36% and 27% RPS in B8 and B12 groups. Based on these results, it can be concluded that supplementation of biofloc even at 4% level in the feed improves immune responses and metabolic activities in black tiger shrimp juveniles.