A preliminary assessment of growth and production of Nile tilapia, Oreochromis niloticus L., Fed Azolla-based-diets in earthen ponds

The effects of the use of Azolla filiculoides Lam., as an alternative source of protein, on growth performances and production of Nile tilapia, Oreochromis niloticus, reared in wetland ponds was evaluated. Three isonitrogenous (27% CP) and isocaloric (4019.14 kcal/g) diets A0, A10, and A20 containing three levels of Azolla 0, 10, and 20, respectively, as a partial substitution of fish meal, were fed to three triplicate ponds of male O. niloticus (initial mean weight = 15.5 g). The Azolla-free diet (0% Azolla) served as a control. The growth performances and production are good in all treatments after 90 days of experiment. No significant differences among dietary treatment (P > 0.05) were noticed for daily growth rate (1.15 g/day-1.26 g/day), specific growth rate (2.27-2.35%/day), survival (74.78-77.43%), annual fish production (31.01-32.75 kg/are/year), and feed conversion ratio (1.06-1.13). Thus, similar growth and production performances were observed with fishes fed with A0 and those fed with A20. Therefore, up to 20% of Azolla in the ration of O. niloticus has no negative effect on either growth or production. The cost-benefit analysis showed a considerable reduction in the production costs of one kilogram of fish with increasing Azolla levels in diet, amounting to US$0.09 between A0 and A10 (P > 0.05) and US$0.14 between A0 and A20 (P <0.05). These results indicate that, on an isonitrogenous and isocaloric basis, using Azolla at up to 20% in a diet can constitute a viable alternative source of protein for O. niloticus in tropical wetlands. © 2007 The Haworth Press, Inc. All rights reserved.