Journal of Science and Technology Research, Volume 4, Number 4, 2005 ISSN 1596-9649 EFFECTS OF SUBSTITUTING SOYABEAN MEAL FOR MAGGOT MEAL ON ACCEPTABILITY OF DIETS, GROWTH PERFORMANCE AND COST BENEFIT OF DIETS FED TO HYBRID CATFISH - HETEROBRANCHUS BIDORSALIS (%) X CLARIAS GARIEPINUS (&) Eyo, Joseph Effiong Department of Zoology, University of Nigeria, Nsukka ABSTRACT The acceptability of maggot meal based diets by the juveniles hybrid of Heterobranchus bidorsalis (%) x Clarias gariepinus (&) was studied using the “time to strike and acceptability index”. The growth potentials of the hybrid Heterobranchus bidorsalis (%) x Clarias gariepinus (&) juveniles fed maggot meal based diets were studied using “weight gain and specific growth rate”. Furthermore, the cost benefit of feeding 1000 hybrid of Heterobranchus bidorsalis (%) x Clarias gariepinus (&) juveniles for ten weeks with maggot meal based diets was estimated. The results indicated that substituting soya bean meal with maggot meal in diets fed to the hybrid of Heterobranchus bidorsalis (%) x Clarias gariepinus (&) juveniles lowered the time taken by fish to strike dietary pellets. Diet containing 0 % maggot meal (diet A – control) was not easily struck by catfishes when compared with the diet containing 100 % maggot meal (diet G). The higher the proportion of maggot meal in the diet, the higher the acceptability of the diet to fish. The most acceptable diet was diet G with 100 % maggot meal. Increasing substitutions of soya bean meal with maggot meal in diets fed to the hybrid Heterobranchus bidorsalis (%) x Clarias gariepinus (&) juveniles led to minor weight decreases and lower growth induction in catfishes fed diets C, D, F and G. These diets had lower mean weight gains and growth rates than the control (diet A). Furthermore, increased substitutions of soya bean meal with maggot meal in diets fed to Heterobranchus bidorsalis (%) x Clarias gariepinus (&) hybrid juveniles led to reduction in the cost of diets. The cost benefit analysis revealed that catfishes fed diet B (10 % maggot meal based diet) had comparatively lower cost of diet per unit weight gain than catfishes fed the control diets and other maggot meal based diets. The benefits derived by both the catfishes and the fish farmer due to the replacement of up to 10 % soya bean meal with maggot meal in diets of the hybrid of Heterobranchus bidorsalis (%) x Clarias gariepinus (&) are discussed. Key words: Maggot meal, Acceptability, Growth, Heterobranchus bidorsalis, Clarias gariepinus, Hybrid INTRODUCTION Fish is the most numerous vertebrate with estimates of around 20,000 described species (Lagler et al. 1977). They account for 48.1% of vertebrates species and are known to occur in all waters; fresh, brackish and marine and at all depths. In many parts of the world particularly in the developing countries, the importance of fish as a less expensive source of protein cannot be over-emphasized. In these countries, first class protein [meat, egg, milk] are expensive and often beyond the reach of many. Apart from being relatively cheaper than meat, fish contains quality amount of essential amino acids such as lysine, methionine and tryptophan, and is also richer in vitamins and minerals (Pearson, 1973). For these reasons, most countries in the tropics have turned their attention to the exploitation, development and sustainable management of their fisheries resources as a means of providing their citizen with the much needed animal protein among other benefits. In Nigeria the demand for fish is in excess of its exploitation and supply, and the shortfall has often been made up through importation and in the recent times partially through aquaculture. This high demand for fish protein is due to rapid population increase, awareness of fish protein quality, relatively high cost of all animal proteins other than fish protein and the general poverty level. Furthermore, the high demand of fish has made us to know that captured fish alone cannot meet our ever increasing market demand (Dim, 1982). The supply and the quality of fish from the wild correlates with unmanaged exploitation and unpredictable yield. In Nigeria, to satisfy the steady growing demand for fish, one option which until recently has not been given much attention is aquaculture. Currently, most endeavours are government sponsored fish farms with only very few individual concerned. The species of fish culture include, Clarias, Tilapia, Dystichodus, Heterotis, Chrysichthys, Heterobranchus etc (Eyo, 1997). Since the growth, development and reproduction of fish takes place at the expense of the energy derived from food. The practice of supplemental feeding of fish and the improvement of the quality of fish diet production should be of great importance. But according to Eyo (1997), the techniques and technology associated with fish diet production, use and management has experienced slow development in the tropics. With exception of government and institutional own fish farm, most traditional fish farm have been extensively managed. Where cultured fish are fed, such feeding has been irregular and limited to small variety of unprocessed feed stuffs [agro-waste] often of low nutritional value and unpalatable. Mgbenka (1988), reported that fish feed is the single most contribute to operation cost in any meaningful aquaculture, accounting for over 50% of the total cost. On this note, Eyo (1997) had earlier pointed out that it is advisable to prepare the fish diet in such a form that will be most acceptable to fish so as to reduce feed wastage. The