Effect of adding nanoparticle magnetite (Fe3O4-NPs) and probiotics in feed on the growth performance of catfish (Clarias batrachus)

The limited availability and low bioavailability of inorganic iron in conventional fish feed can hinder optimal growth and health in fish. Therefore, this study evaluates the effectiveness of Fe₃O₄-NPs as a nutritional supplement in catfish (Clarias batrachus) feed. Fe₃O₄-NPs were synthesized via the coprecipitation method, producing cubic crystalline particles averaging 11.99 ± 0.42 nm in size. These nanoparticles were incorporated into a fish diet containing fish meal, rice bran, soybean meal, cornmeal, fish oil, and vitamin C, along with probiotics (Lactobacillus plantarum (1 × 10⁹ CFU/mL), Bacillus sp., (3 × 10⁷ CFU/mL) L. acidophilus (6 × 10⁸ CFU/mL), and 3 g Saccharomyces carasiviae) to enhance digestion and nutrient absorption. Three experimental feeds with Fe₃O₄-NPs doses of 30, 60, and 120 mg/kg were prepared and compared to commercial feed as a control. Parameters evaluated included feed physical and chemical characteristics, fish growth performance, feed efficiency, survival rate, histology of gills, liver, and muscle, as well as heavy metal content in water and fish flesh. Basal Feed 60 mg/kg dose Fe₃O₄-NPs (BF60) yielded the best results, with optimal growth performance (protein efficiency ratio (PER): 0.50; specific growth rate (SGR): 1.57%/day), high survival rate, and normal tissue morphology. Histological observations indicated no toxicity, and heavy metal levels in fish flesh from BF60 remained below FAO (2021) safety limits: Zn (17.849 mg/kg), Fe (4.695 mg/kg), Cu (0.800 mg/kg), with other metals undetected. These findings indicate that 60 mg/kg Fe₃O₄-NPs is a safe and effective dietary supplement for improving catfish growth performance and health.