Effects of dietary iron oxide nanoparticles on the growth performance, biochemical constituents and physiological stress responses of the giant freshwater prawn Macrobrachium rosenbergii post-larvae

This study was performed to assess the growth promoting potential of dietary Fe2O3 NPs in Macrobrachium rosenbergii PL. Fe2O3 NPs was supplemented at 0, 10, 20, 30, 40 and 50 mg kg-1 with the basal diet (containing 5.45 mg Iron kg-1). The concentration of Fe in Fe2O3 NPs supplemented diet was increased correspondingly. Fe2O3 NPs supplemented diets were fed to M. rosenbergii PL (initial weight, 0.11±0.04 g) for a period of 90 days. In the carcass of experimental prawns, the content of Fe was found to be elevated significantly when compared with control. Similarly, Cu, Zn, Ca, Mg, Na and K levels were also elevated. Therefore, the supplemented Fe2O3 NPs were taken up and incorporated into the body of the prawns, which facilitates absorption of other minerals as well. Significant (P < 0.05) improvements were observed in survival, growth, activities of digestive enzymes (protease, amylase and lipase), concentrations of basic biochemical constituents (total protein, amino acid, carbohydrate and lipid, profiles of amino acids and fatty acids) and population of haemocytes [total and differential (hyalinocytes, semigranulocytes and granulocytes)] at 10 and 20 mg kg-1 Fe2O3 NPs supplemented feeds fed prawns, whereas, 30-50 mg kg-1 Fe2O3 NPs supplementations showed negative performance. The polynomial regression analysis revealed that a dietary requirement of 24.56 mg kg-1 Fe2O3 NPs for optimal growth of prawns. SDS-PAGE revealed separation of 14 polypeptide bands in the muscle of prawns. Among these, the staining intensity of 116, 99, 50, 26, 20, 18, 15, 14 and 13 kDa polypeptide bands were found to be higher in 20 mg kg-1 Fe2O3 NPs supplemented feed fed prawn when compared with control. The lowest food conversion ratio (FCR) recorded in 20 mg kg-1 of Fe2O3 NPs supplemented diet fed PL reflects the superior quality of the diet prepared. Therefore, up to optimum level supplementation of Fe2O3 NPs, the general health of the experimental prawns was improved due to its incorporation in the body. But beyond the optimum level it turned towards toxic. Therefore significant (P<0.05) elevations in activities of antioxidant enzymes (superoxide dismutase and catalase), lipid peroxidation, and metabolic enzymes (glutamic oxaloacetic transaminase and glutamic pyruvic transaminase) were recorded in 30-50 mg kg-1 Fe2O3 NPs supplemented diets fed prawns. The better profiles of protein, amino acids, fatty acids, biochemical constituents and haemocytes helped to attain appreciable survival and growth of M. rosenbergii PL. Thus, this study recommends Fe2O3 NPs supplementation up to 20 mg kg-1 for its sustainable maintenance.