The Biofloc system potential in reducing dietary protein levels for tambaqui

Abstract This study aimed to compare tambaqui (Colossoma macropomum) aspects when offered different feed protein levels and the water quality of a biofloc (BFT) system vs. a clear water (CW) system. Tambaqui juveniles (9.20 ± 0.23 g) were randomly distributed employing a 2x3 factorial experimental design to evaluate a BFT and CW system and three dietary crude protein (CP) levels (24, 28 and 32% CP) for 60 days. Decreased pH and nitrite (p < 0.05) and increased electrical conductivity, nitrate, turbidity, settleable solids and total suspended solids were observed in the BFT system compared to the CW system (p < 0.05). Tambaqui zootechnical performance in the BFT system indicated better feed conversion, final weight, weight gain, biomass, productivity, specific growth rate and protein efficiency rates and 100% survival for all CP treatments in relation to the CW system. No differences (p > 0.05) were detected in tambaqui nutritional composition and digestive enzymes, except for trypsin, which presented higher activity in fish reared in the BFT system. No statistical differences concerning performance indices were noted for CP levels, regardless of the rearing system, although the results suggest better tambaqui adaptive capacity in the BFT system, through better use of the natural food produced in this system. This estudy indicates that feed containing 24% CP may be offered to tambaqui in both systems, although the BTF system is more efficient for tambaqui farming activities.