Effect of production systems and dietary protein levels on the growth performance of juvenile Piaractus brachypomus

The sustainable intensification of aquaculture requires efficient production systems and cost-effective nutritional strategies. In this context, Piaractus brachypomus stands out due to its rapid growth and adaptability to different farming systems. This study evaluated the zootechnical performance of juvenile P. brachypomus reared in recirculating aquaculture systems (RASs) and biofloc technology systems (BFTs), and fed diets containing 24% and 32% crude protein (CP). The experiment was conducted over 90 days using a 2 × 2 factorial design with three replicates per treatment. Each experimental unit (800 L) contained 15 fish (174.71 ± 2.80 g). The evaluated parameters included final weight, final length, weight gain, daily weight gain, specific growth rate, final biomass, biomass gain, apparent feed conversion ratio, and survival. Data were analyzed using two-way ANOVA followed by Tukey’s test (p < 0.05). No interaction was observed between culture system and dietary protein level for any of the analyzed variables (p > 0.05). The production system did not influence the evaluated zootechnical parameters (p > 0.05), indicating similar fish performance in both RAS and BFT, with final weight close to 445 g, feed conversion ratio ranging from 1.73 to 1.91, and survival rates above 92%. Fish fed the 24% CP diet showed greater weight gain (294.86 g), higher daily weight gain (3.27 g day⁻¹), and higher specific growth rate (1.64% day⁻¹) compared to those fed the 32% CP diet (244.86 g, 2.72 g day⁻¹, and 1.45% day⁻¹, respectively). The results demonstrate the high productive potential of juvenile P. brachypomus in both evaluated systems, indicating the possibility of using diets with lower protein content without impairing growth performance or productive efficiency of the species. Financial support: CNPq and CAPES.