Heterotis niloticus is an African species with a great potential for fish farming as a result of its remarkably rapid growth, air-breathing characteristic, omnivorous diet, good meat quality and relative high commercial value. However, its use for aquaculture is limited due to the difficulty in the massive production of fingerlings and the lack of knowledge on its artificial feeding. Therefore, the estimations of its nutritional requirements at different ontogenetic stages are necessary in view of its effective contribution to the aquaculture production in Cameroon and other African countries. The present research aims to establish some basic nutritional variables relative to its fingerlings rearing and to examine the suitability of plant oil cakes as a partial substitute of fish meal in its compounded diets. Between May 2005 and August 2008, several experiments were conducted in rectangular hapas (0.5 m3 useful capacity) placed in two earthen pond (300 and 600 m²) at the Melen Aquaculture Station (Yaounde, Cameroon). Replicate groups of juveniles were handfed twice daily to apparent satiation all the time. Analyses were performed at the laboratory of the Research Unit in Organismal Biology (University of Namur, Belgium) and the Unit of Industrial Chemistry Biology (Gembloux Agricultural University, Belgium). On the protein and amino acids requirements, the results revealed that the dietary protein requirements are 310 and 345 g protein per kg diet for optimal and maximal growth, respectively for fish size ranging from 3 to 62 g. Based on whole body or muscle tissue indispensable amino acids to A/E ratios, its IAA requirement profile is similar to those of other omnivorous tropical fish species with the exception of tryptophan and histidine. The dietary protein-sparing effect has been clearly demonstrated when the dietary energy of lipid increases from 17 to 19.6 kJ g-1 at 28% crude protein. Therefore, this result indicates that the optimum protein and lipid levels in its diet are 280 and 130 g kg-1 diet, respectively. Finally, the soybean and cottonseed oilcakes meals could partially replace up to 50% the dietary fish meal in its practical fingerlings diets without negative effect on maximal growth. This study contributes to improve our knowledge on basic nutrients requirements for the juveniles of a new aquaculture species for Africa. However, massive production of quality fingerlings of this species remains a major obstacle to overcome on the road of the domestication of H. Niloticus for aquaculture use. Our work reveals that even with that constraint, optimism is permitted for a sustainable and rentable culture of this species in sub-Saharan Africa.
|Date of Award||6 Mar 2009|
|Supervisor||Patrick KESTEMONT (Supervisor), Victor Pouomogne (Co-Supervisor), Bernard Wathelet (Jury), C. Mélard (Jury), Robert Mandiki (Jury) & Jean-Loup BISTER (Jury)|