Zootechnical Performance and Some Physiological Indices of Tambaqui, Colossoma macropomum Juveniles during Biofloc Maturation and in Different Feed Regimes

The objective was to evaluate the hematological and biochemical blood parameters and performance of Colossoma macropomum submitted to BFT maturation and under different feeding regimes. BFT maturation was carried out for 60 days (Phase 1). Feeding on six or seven days a week and feeding rates of 4% or 6% of biomass were tested (Phase 2). The water quality parameters were monitored throughout the experimental period. At the end of Phases 1 and 2, blood samples and zootechnical performance were evaluated. In Phase 1, total ammonia was higher on the 17th day (1.25 mg TAN L −1 ) and stabilized from the 21st day onwards. Nitrite reached a peak (9.67 mg L −1 ) on the 26th day. There was an increase in nitrate between the 25th and 60th day (1.79 ± 0.01 vs. 5.45 ± 0.01 mg N-NO 3 − L −1 , respectively). FCR (1.90 ± 0.21), weight gain (9.81 ± 1.08 g), and SGR (1.26 ± 0.12%) were highest at 30 days of phase 1. The glucose level (118.23 ± 26.30 mg dL − 1 ) was highest on the 30th day. The plasmatic protein (5.36 ± 0.30 g dL −1 ) and alanine aminotransferase (ALT) levels (27.58 ± 6.58 UI mL − 1 ) were highest after 60 days. The hemoglobin level (5.77 ± 0.74 g dL − 1 ) was lowest after 30 days. In Phase 2, the triglycerides, ALT, and hematocrit levels were different at the end of the experiment under all feeding regimes. Histological analysis of gills showed a normal condition for fish under BFT. It was possible to apply a feeding regime of six days a week and 4% biomass for juveniles, with 43 g on average.