12 June 2010 Use of discarded cocoa bean meal as a source of dietary energy for the production of African catfish (Clarias gariepinus, Burchell 1822) L.C Nwanna1 and O. F. Fashae At least 10 percent of harvested cocoa bean seed (Theobroma cacao) is discarded as waste by-product by cocoa processing industries/communities in Nigeria. Nwanna et al. (2008) described discarded cocoa bean seed as the whole bean unfit for human consumption. The volume of this waste in relation to the total quantity of cocoa produced annually attracted the interests of some scientists who opined that the product could be used in animal feeds. Adegbola and Omole (1973) characterized the chemical and amino acid composition of the discarded cocoa bean seed meal. They reported that the bean has great potential as an alternative animal feed. The proximate composition reported was supported by our earlier investigation (Nwanna et al. 2008). However, as nutritionally rich as this alternative feed ingredient is, there is a dearth of information on its use as a dietary energy source in fish nutrition. Energy feedstuffs are low in protein and contain about 12 percent crude protein, of which 75-80 percent is digestible (Fagbenro et al. 2000). They are also useful as texturing and binding agents in pelleted feeds. Corn is usually used as a dietary energy source in fish feed. It contains 65-75 percent starch, 10 percent protein, 3.5-5 percent lipid, while the outer tissue of the grain contains vitamins (Purseglove 1985). Most fish feed formulations contain between 20-30 percent corn. As a dietary carbohydrate, corn has the ability to reduce the oxidation of dietary protein for energy (Viola and Arieli 1983, Hanley 1993, Nwanna et al. 2003) that invariably minimizes the quantity/costs of dietary protein. However, competition for its use in human foods and animal feeds limits the availability/quantity and, hence, increases the price. This has necessitated research to find cheaper alternative non-conventional energy sources that will not compromise growth and physiological functions. Inasmuch as the nutritional quality of discarded cocoa bean seed meal (protein 16 percent, fat 45.1 percent, carbohydrate 19 percent) compares favorably well with that of yellow corn (Nwanna et al. 2008), it may be hypothesized that discarded cocoa bean meal (DCM) can adequately replace corn in fish diets. The present study investigated the effect of replacement of yellow corn with discarded cocoa bean seed meal on the growth and nutrient utilization of African catfish (Clarias gariepinus). Economic implication of the replacement was estimated using the incidence of cost and profit index model of Vincke (1969) by assuming 50 percent of the cost of corn for the DCM. Study Materials and Methods Sample collection and preparation The discarded cocoa bean seed used for the study was collected on March 2008, from Stanmark Cocoa Processing Company, Ondo Road, Akure in Ondo State. Thereafter, the cocoa beans were sundried at a temperature of 27-30ºC to make the husk easier to remove. The husks were mechanically removed by hand and the inner cocoa pods were sundried again. The dried pods were blended into fine particles to form the DCM. Diet preparation Other feedstuffs including, fishmeal, soybean meal, ground nut cake, yellow corn, cod liver oil, vitaminmineral premix, methionine and carboxymethy cellulose (Table 1) were purchased from Adedom Feeds Vendor, Akure in Ondo State. The required quantities of each ingredient making up a 40 percent crude protein diet were mixed together and pelleted to provide the basal diet or control diet, diet 1. Then, in diets 2, 3, 4, and 5, DCM replaced 25, 50, 75 percent and 100 percent of the corn in the basal diet, respectively. The dried feed ingredients were mixed with the vitamin-mineral premix, starch and DLmethionine and a small amount of water and made into 1-mm diameter pellets. The pellets were sun dried to a constant moisture level (<10 percent), packed in airtight polyethylene bags and stored at -20ºC before use. Diet samples were analysed for their proximate composition (Table 2) using the methods of AOAC (1990). Gross energy of the diets was calculated using KJ/g) values of 23.0, 38.1 and 17.2 for protein, lipid and carbohydrate, respectively (Tacon 1990).
RkJQdWJsaXNoZXIy MjExNDY=