Variation of dietary protein/lipid levels used in postlarvae of freshwater prawn Macrobrachium rosenbergii cultured in a biofloc system

A 70-day experimental trial was performed to evaluate the contribution of biofloc to the nutrition of Macrobrachium rosenbergii 15 days old postlarvae (PL) (average 82.00 ± 19.71 mg) fed different crude protein (P) and lipids (L) levels in zero-water exchange culture tanks. Six biofloc treatments (BFT) as experimental diets with 15, 20, or 25% P levels and 5 or 8% L levels were managed: BFT-15/5; BFT-15/8; BFT-20/5; BFT-20/8; BFT-25/5; BFT-25/8, and a clear-water control without biofloc fed with 25% P and 8% L (CW-25/8). The experiment was done in triplicate in 21-60 L plastic tanks containing 10 prawns tank-1. At the end of the experiment, survival of prawns was above 66%, with no significant differences among experimental groups (P > 0.05). The best growth performance was observed in the experimental prawns maintained in BFT-20/5, BFT-20/8, BF-25/5, and BFT-25/8 compared to the control (P < 0.001). The feed conversion rate of the prawns in BFT-20/5 was significantly lower than that in control (P < 0.001); the best P efficiency ratio and productive P value were observed in all BFT compared to control prawns (P < 0.001). Results showed that it is feasible to use low concentrations of P (20%) and L (5%) in diets to grow giant freshwater prawn PL in a biofloc system. Results also demonstrated that biofloc contributes to the P and L requirements of cultured freshwater prawn PL, as indicated by improved feed utilization, P retention, and growth performance.