Effect of Dietary Protein and Energy Levels on Growth, Feed Utilization and Body Composition of Juvenile African bonytongue (Heterotis niloticus)

Abstract

Background and Objective: In Cote d’Ivoire, the tilapia Oreochromis niloticus is the major species in fish farming, but its production remains low because of the high cost of feed for this fish. Several species with aquaculture potential exist but are produced on a small scale by a few fish farmers. The diversification of fish species through large scale farming of African bonytongue Heterotis niloticus (H. niloticus) is an option to increase fish production and ensure the sustainable development of aquaculture. The aim of this study was to determine the level of dietary protein and energy for optimal growth of H. niloticus juveniles to produce feed based on local agricultural by-products for the intensive production of this species. Methodology: An 80 day feeding trial was conducted in hapas installed in earthen ponds to evaluate the effects of dietary protein and energy levels on growth, feed utilization and body composition of H. niloticus fingerlings. Fingerlings with an initial body weight of 17.83±0.45 g were fed 16 experimental diets formulated to contain 4 protein levels (25, 30, 35 and 40%) and 5 levels of gross energy (17, 18, 19, 20 and 21 kJ g^–1) with three replicates per treatment. Results: Final body weight (FBW), specific growth rate (SGR) and feed conversion ratio (FCR) varied significantly with dietary protein level. For the same dietary protein level (25% and 30%), FBW and SGR increased with the increase in dietary energy content. Beyond 40% protein level, further increase in energy level (18 to 21 kJ g^–1) caused a decline in FBW. FCR increased with increasing protein and decreasing energy level in their diet, whereas protein efficiency ratio (PER) decreased with increasing dietary protein and increasing energy level. The whole-body protein and lipid contents were significantly affected by dietary protein level, but whole body composition was not significantly affected by energy level. The results indicate that the best total production (3.94±0.43 t ha^–1 year^–1), SGR (3.72±0.05% day^–1), FCR (0.75±0.01) and PER were obtained with fish fed on a diet containing 30% dietary protein and a gross energy level of 19 Kj g^–1. Conclusion: We suggest that a diet with 30% dietary protein and 19 kJ g^–1 is recommended for the best growth at this specific stage of H. niloticus fingerlings.