Effect of Four Treated Forms of Lemna minor on Zootechnical Balance and Digestive Performance of Juvenile Tilapia (Oreochromis niloticus) in Côte d'Ivoire (West Africa)

Abstract

Background and Objective: The incorporation rate of fish meal in compound feeds of aquaculture is currently reduced due to the higher demand and price. This study was conducted to assess the nutritional value and digestive utilization of four treated forms of Lemna minor in the diet of tilapia. Materials and Methods: Four treatments (shade-drying, oven drying, pre-cooking-drying and fermentation-drying) were applied to reduce anti-nutritional factors (oxalate, phytates, tannins and saponins). Four experimental diets, each including 70% of reference diet and 30% of treated forms of L. minor, were formulated. After 8 weeks of feeding in hatchery of aquaria, faeces were sampled for analyses. Results: The results showed that the reduction of anti-nutritional factors by the three heat treatments was less than 30% for oxalate, while tannins, phytates and saponins were reduced from 50-90%. The best reduction rates (90%) were found with fermented L. minor for tannins, phytates and saponins and 30% for oxalate. The study revealed high apparent digestibility coefficients (ADC) in proteins (81.68%) and energy (78.47%) for fish fed with fermented L. minor. Low digestive coefficients in protein (65.56%) and energy (62.20%) was observed for fish fed with pre-cooked-dried L. minor, while high digestible protein content (33.16 mg g^–1) was observed for fermented leaves. Fermented leaves diet had the highest protein retention coefficient (47.56%) and the pre-cooked-dried leaves diet had the lowest value (14.30%). Conclusion: In Côte d'Ivoire, fermented L. minor could be used as a protein supplement in fish feed formulation.