Effects of iron oxide nanoparticles, vitamin C, and vitamin E on growth performance and hematological indices of Cyprinus carpio

Abstract Background Aquaculture productivity depends on efficient nutritional strategies that enhance growth, survival, and physiological health of cultured fish. Iron oxide nanoparticles (Fe₂O₃-NPs) have shown potential as dietary supplements due to their high bioavailability, while vitamins C and E may support growth and feed efficiency. This study evaluated the effects of green-synthesized Fe₂O₃-NPs, alone and in combination with vitamins C and E, on the growth performance and hematological parameters of Cyprinus carpio. Methods A total of 540 juvenile C. carpio were randomly distributed into six dietary treatment groups and reared for 8 weeks. The study used a factorial dietary design with six treatments and three replicate tanks per treatment. Fish were fed a basal diet (control) or diets supplemented with Fe₂O₃-NPs at 4.5 or 9 mg kg⁻¹, with or without 250 mg kg⁻¹ vitamins C and E. The Fe₂O₃-NPs were green-synthesized using Azadirachta indica leaf extract and characterized by SEM, FTIR, and XRD. Growth performance indices, survival, and a limited panel of hematological parameters (excluding hemoglobin, which was omitted due to instrument verification issues) were assessed at the end of the feeding trial; results are presented as mean ± standard deviation (SD). Results Feeding Fe₂O₃-NPs significantly improved growth performance, particularly when combined with vitamins C and E. The highest final weight, weight gain (8.02 ± 1.79 g), percentage weight gain (177.02%), specific growth rate (0.492), and best feed conversion ratio (1.56) were observed in fish receiving 9 mg kg⁻¹ Fe₂O₃-NPs + vitamins C and E (T₄). Survival reached 100% in all Fe₂O₃-NP-supplemented groups (T₁–T₄). Platelet counts differed significantly among treatments ( p < 0.05), whereas most other measured hematological parameters showed no significant differences ( p > 0.05). Hemoglobin data were excluded because the automated analyzer output exceeded known physiological limits for Cyprinus carpio and could not be reliably verified; consequently, oxygen-carrying capacity was not evaluated. Conclusion Dietary supplementation with green-synthesized Fe₂O₃-NPs, particularly at 9 mg kg⁻¹ in combination with 250 mg kg⁻¹ vitamins C and E, improved growth performance, feed utilization, and survival, and modulated platelet counts in Cyprinus carpio. No significant changes were observed in the other hematological parameters assessed (excluding hemoglobin). These findings suggest that combined Fe₂O₃-NP and antioxidant vitamin supplementation may be a promising dietary approach, but long-term safety studies including full hematological profiling and histological evaluation are required before commercial application can be recommended.