Evaluation of fermented Azolla leaf meal-based diet on growth and nutrient bioavailability in Nile tilapia ( Oreochromis niloticus ) fingerlings

Abstract

Rising demand for affordable and sustainable aquafeeds has increased interest in plant-based ingredients. In this regard, Azolla pinnata , a fast-growing aquatic fern with high protein content and rapid biomass production, is recognized as a promising aquaculture feed ingredient. This study evaluated fermented A. pinnata as a substitute for fishmeal to improve growth indicators, nutrient utilization, hematological parameters, body composition, and uptake of minerals in Nile tilapia ( Oreochromis niloticus ) fingerlings. Six diets were formulated with graded levels of fermented A. pinnata leaf meal (FALM): 0% (control), 10%, 20%, 30%, 40%, and 50% replacement of fishmeal. Nile tilapia ( O. niloticus ) fingerlings with an average initial weight of 6.18 g were randomly assigned using a completely randomized design and fed at 4% of their body weight twice daily for a period of 70 days. ANOVA (one-way) with Duncan's multiple range test verified significant differences ( P  < 0.05) among all treatments. Results demonstrated that the 30% (FALM) diet IV produced significantly superior outcomes ( P  < 0.05), with the highest final weight (26.46 g), weight gain (20.28 g), specific growth rate (2.08%/day), and the lowest feed conversion ratio (1.25). The 30% FALM diet yielded significantly superior results for crude protein (72.28%), fat (69.55%), and gross energy (69.63%) compared with the other dietary treatments. This level also resulted in optimal hematological parameters, with red blood cell count reaching 3.25 × 10 6 mm -3 , hemoglobin at 8.89 g/100 ml, and packed cell volume at 31.61%. At this inclusion level, carcass composition recorded the significantly highest crude protein (18.84%) and fat content (9.11%), while mineral absorption of calcium (74.64%), phosphorus (75.14%), potassium (73.74%), and sodium (76.64%) also peaked. These findings indicate that FALM can substitute up to 30% of fishmeal in O. niloticus diet, providing an eco-friendly protein source while maintaining growth performance and overall health profile.