Oxidative stress biomarkers in juvenile Piaractus brachypomus cultured in RAS and BFT under different crude protein levels

Modern aquaculture requires efficient production systems combined with nutritional strategies capable of reducing costs and environmental impacts. In this context, the present study evaluated the effects of recirculating aquaculture systems (RASs), biofloc technology systems (BFTs), and diets containing 24% or 32% crude protein (CP) on oxidative stress biomarkers in juvenile Piaractus brachypomus. The experiment was conducted using a 2 × 2 factorial design, with two culture systems and two diets, totaling four treatments with three replicates over 90 days. Each experimental unit consisted of 15 fish (174.71 ± 2.80 g) stocked in 800L tanks. At the end of the trial, liver samples from five fish per experimental unit (n = 15) were collected to evaluate hepatic oxidative stress biomarkers, including thiobarbituric acid reactive substances (TBARSs), total glutathione (GT), ascorbic acid (AA), total antioxidant capacity (TAC), catalase (CAT), and glutathione S-transferase (GST). Data were analyzed using two-way ANOVA followed by Tukey’s test (p < 0.05). The results demonstrated a significant effect of culture system on TBARS levels, with higher values observed in fish reared in a BFT (5.80 ± 1.27 nmol g⁻¹) compared to those maintained in an RAS (3.39 ± 0.82 nmol g⁻¹). Likewise, fish fed the 32% CP diet showed higher TBARS concentrations (5.23 ± 1.84 nmol g⁻¹) than those fed the 24% CP diet (3.96 ± 1.18 nmol g⁻¹). However, GT, AA, TAC, CAT, and GST did not differ among treatments (p > 0.05). No interaction was observed between production system and dietary protein level for any analyzed variable (p > 0.05). The results indicate that BFT conditions and higher dietary protein levels may increase susceptibility to lipid peroxidation in P. brachypomus without impairing the evaluated hepatic antioxidant defense mechanisms. Financial support: CNPq and CAPES.