Effect of graded levels of dietary ascorbic acid on the metabolic and redox modulation of intensively reared juvenile pikeperch (Sander lucioperca)

This study evaluated the effects of graded dietary ascorbic acid (AA) supplementation on growth performance and physiological parameters of intensively cultured pikeperch (Sander lucioperca). Fish were fed diets containing 0 (G0), 27 ± 1.8 (G30), 108 ± 11.4 (G100), 311 ± 11.6 (G300), 809 ± 40.8 (G800), and 1963 ± 33.1 (G2000) mg AA.kg−1 of feed for 112 days in a recirculating aquaculture system (RAS). Each treatment was conducted in triplicate with 150 juveniles per tank (initial body weight 37.9 ± 7.91g). Growth performance, feed utilization, survival (>97.8%), and organosomatic indices did not differ among tested treatments. Blood biochemical analysis revealed modulation of selected metabolic parameters, including reduced LIP activity and elevated TG at higher dietary AA levels, while the indicators of hepatic integrity (ALT, AST, HSI) remained unchanged. Tissue AA concentrations increased dose-dependently in both liver and muscle, confirming effective dietary incorporation and bioavailability. Two highest dietary AA levels (800–2000 mg kg−1) significantly altered oxidative-stress markers as follow: SOD and CAT activities in mucus increased, whereas TBARS increased in both mucus and blood, accompanied by elevated GSH and GST in blood. This pattern indicates activation of compensatory antioxidant mechanisms in response to increased oxidative load rather than improved oxidative stability. Under standard RAS rearing conditions, increasing dietary AA beyond basal levels did not enhance growth or overall physiological performance in juvenile pikeperch but induced redox and metabolic modulation at higher inclusion levels which is very important for future successful growth-out pikeperch intensive culture. The present study indicates that increasing dietary ascorbic acid at higher inclusion levels 800–2000 mg kg−1 does not enhance growth and survival of juvenile pikeperch under intensive conditions but induces measurable metabolic and redox modulation. Dose-dependent tissue accumulation confirms effective incorporation of AA, while associated changes in oxidative-stress markers suggest adaptive physiological responses rather than improved functional status. These findings help refine understanding of AA-related redox regulation in pikeperch and indicate that supplementation beyond basal requirements may not provide additional production benefits under standard rearing conditions.