Hematological and biochemical responses of juvenile Piaractus brachypomus cultured in RAS and BFT under different dietary protein levels

Hematological and biochemical parameters are important physiological indicators of fish health and metabolic responses in intensive aquaculture systems. This study evaluated the hematological and biochemical responses of juvenile Piaractus brachypomus cultured in recirculating aquaculture systems (RASs) and biofloc technology systems (BFTs), and fed diets containing 24% and 32% crude protein (CP). The experiment lasted 90 days and followed a 2 × 2 factorial design with three replicates per treatment. Each experimental unit consisted of 15 fish (174.71 ± 2.80 g) stocked in 800 L tanks. At the end of the experimental period, blood samples were collected from five fish per unit, totaling 15 fish per treatment. Hemoglobin, hematocrit, erythrocytes, MCV, MCH, MCHC, total proteins, albumin, globulin, glucose, triglycerides, chlorides, cholesterol, VLDL, ALT, AST, and urea were evaluated. Data were analyzed using two-way ANOVA followed by Tukey’s test (p < 0.05). An interaction effect was observed for hematocrit and serum chlorides (p < 0.05). Fish reared in RASs showed higher hemoglobin (10.97 g dL⁻¹), hematocrit (32.27%), total proteins (2.98 g dL⁻¹), albumin (1.23 g dL⁻¹), glucose (59.85 mg dL⁻¹), and cholesterol (180.28 mg dL⁻¹) compared to fish cultured in BFTs, which presented lower values for these parameters (p < 0.05). Regarding diets, fish fed 32% CP showed higher hemoglobin (11.12 g dL⁻¹), hematocrit (31.90%), and AST activity (66.96 U L⁻¹), whereas fish fed 24% CP presented higher ALT levels (7.29 U L⁻¹) (p < 0.05). No differences were observed for erythrocytes, triglycerides, globulin, VLDL, or urea between treatments (p > 0.05). The results indicate that both culture system and dietary protein level modulate the physiological responses of P. brachypomus, contributing to the understanding of species adaptation in intensive aquaculture systems. Financial support: CNPq and CAPES.