Effects of Mineral Proteinate Mixture Inclusion Levels on Oncorhynchus mykiss Fry: Growth, Digestion, and Antioxidant Status

To improve growth, digestion, antioxidant status, and feed efficiency, this study sought to identify the ideal inclusion level of an organic mineral mixture (OMM®; proteinates of Zn, Cu, Mn, Fe, Co, Se) to partially replace inorganic mineral premixes in rainbow trout (Oncorhynchus mykiss) fry diet. Four isoproteic diets (0% control, 0.5% OMM-50, 0.75% OMM-75, 1.0% OMM-100) were subjected to triplicate testing using over 60 days. Final weight (13.55±0.03 g), SGR (3.99±0.02%/day), and trypsin activity (2.46±0.10 U/mg protein), were maximum in the OMM-50 group and lowest FCR (1.02±0.01). Both moderate OMM (0.5–0.75%) increased the SOD (8.79±1.9, 7.67±1.3 U/mg protein) and GPx (0.32±0.11, 0.17±0.06 U/mg protein) activities, decreasing MDA (1.60±0.87, 2.83±0.76 nmol/mg protein), suggesting enhanced antioxidant defense. Conversely, OMM-100 reduced growth (11.19±0.06 g), SGR (3.49±0.18%/day), and survival (84.29±0.82%), but increased feed intake (3.37±0.03%/day), indicating mineral imbalance. The peak of whole-body mineral contents was observed at OMM-50, validating higher bioavailability. Thus, 0.5% OMM replacement optimizes physiological outcomes and offers a sustainable alternative to inorganic minerals in aquafeeds. © 2026, Central Fisheries Research Institute. All rights reserved.