Nano-selenium (nano-Se) removes the detrimental impacts of plant-based diets on the production performance and well-being of common carp (Cyprinus carpio)

Fishmeal (FM) is not a sustainable source of nutrients due to the over-exploitation of fisheries resources and increasing aquafeed costs. Plant protein (PP) sources have been utilized as FM alternatives in diets. A 60-day nutritional experiment was conducted to study the effects of the complete replacement of FM with PP ingredients in diets supplemented with nano-Se on growth performance, plasma physiological and immunological parameters, and liver antioxidant capacity of common carp (Cyprinus carpio). Five experimental diets were prepared, where FM-Control contained 35 % FM, PP-Control contained complete PP ingredients, and NSe1, NSe2, and Nse3 contained complete PP ingredients supplemented with 1, 2, and 3 mg/kg nano-Se, respectively. The growth performance of fish fed the FM-Control and NSe3 diets was higher than in the PP-Control group (P < 0.05). The best feed conversion and protein efficiency ratios were detected in the NSe3 group but were not significantly different from the FM-Control group (P > 0.05). While the highest levels of antioxidant parameters, including reduced glutathione, superoxide dismutase, catalase, and glutathione peroxidase, were detected in the liver of fish fed with the FM-Control diet, the lowest malondialdehyde concentration was measured in the NSe3 group (P < 0.05). Plasma levels of lysozyme activity, alternative complement activity, and total immunoglobulin of the FM-Control and NSe3 groups were significantly higher than in other groups (P < 0.05). The best plasma physiological parameters including the lowest levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, cholesterol, triglycerides, and low-density lipoprotein, and the highest levels of total protein, triiodothyronine (T3), and high-density lipoprotein were observed in fish fed with the FM-Control and NSe3 diets (P < 0.05). These results suggest that FM can be entirely substituted by PP in diets containing nano-Se at 3 mg/kg without harmful impacts on the performance and immunity of common carp.