Fishmeal (FM) is the main source of protein in fish diets, but its supply is stable. So, available plant protein sources could be used instead of FM in aquafeeds. These plants-source proteins may negatively affect feed intake and/or absorption of nutrients due to bad digestion. Therefore, the efficacy of a dietary exogenous enzymes mixture (Hostazyme X; HX) on growth performance, antioxidant capacity, and digestive enzymes in common carp, Cyprinus carpio, was assessed. Dietary HX was included in practical diets at levels of 0.0 (control), 0.1, 0.5, 1.0, and 2.0 g/kg diet. Fish (0.84 ± 0.003 g) were fed on the tested diets up to apparent satiation twice daily in triplicate groups for 8 weeks. The fish performance was significantly improved (P < 0.05) by increasing dietary HX up to 1.0 g/kg diet after which fish growth and feed intake were almost the same. Also, intestinal amylase, lipase, and protease significantly increased (P < 0.05) due to HX supplementation leading to increased feed intake and overall growth performance. Likewise, the antioxidant activity of common carp was stimulated by HX supplementation in a dose-related manner, where the activities of superoxide dismutase, catalase, and glutathione peroxidase were significantly higher (P < 0.05), while malondialdehyde value was significantly lower (P < 0.05) in HX-fed fish groups than those fed the control diet. In conclusion, dietary HX could be used as a feed supplement to confer better growth performance and health of common carp fry with an optimal level of 1.0 g/kg diet.
Keywords: Antioxidant activity; Common carp; Digestive enzymes; Exogenous enzymes; Growth performance.