Tilapia (Oreochromis Niloticus) feeding trial without fish meal using local by-products from the Guinean forest region

An experiment on the feeding of tilapia Oreochromis Niloticus fry of initial weight (6.5±0.0g) was carried out for 56 days in above-ground basins on the site of the University of N'Zérékoré. An open-circuit system of 15 tanks was used to compare five treatments, with 3 tanks per treatment. Five isoprotein diets including one control. The diets tested contained Azolla filiculoïdes (dried), brewer's yeast, earthworms and broiler viscera at various substitution rates, while the control contained fish meal (A₀=29.8%; A₁=30.5%; A₂=30.7%; A₃=31%; A₄=31.9%). The fish were fed three times a day at four-hourly intervals. 

The results showed that physico-chemical parameters such as temperature (28.6±1.2°C), pH (5.59±0.32) and dissolved oxygen content (4.93±0.89 mg/L) during the experiment were within acceptable ranges for the raised species. At the end of the experiment, mean final weights ranged from 10.80±0.54 to 14.90±0.48g, depending on the treatment. Fish fed the A₀ control feed showed a better specific growth rate (1.64±0.103%/d). Specific growth rates obtained in fish fed diets A₁ to A₄ ranged from 1.11±0.10 to 1.26±0.10 %/d. However, the feed conversion rate of diets based on local by-products ranged from 2.32±0.04 to 2.80±0.28. Diet A₄ had a better feed conversion rate than the other diets tested. In terms of economic analysis, treatment A₄ gave a better production cost per kg of O. niloticus. At the end of this study, the optimal rate of substitution of fishmeal by local by-products was set at 31.9%.