Determination of moisture
Moisture was determined by the reduction in weight when the sample was dried to a constant weight in an oven. About 2 g of fish sample was weighed into a silica dish which was previously dried and weighed; the sample was then dried again in an oven at 65°C for 36 h, cooled in a desiccator and weighed. This process was continued until a constant weight was achieved (Oladipo and Jadesimi, 2013). Determination of crude fat
The ether extract of a feed represent the fat and oil in the feed. Soxhlet apparatus is the equipment used for the determination of ether extract. It consists of 3 major components; an extractor: comprising the thimble which holds the sample, a condenser: for cooling and condensing the ether vapor and 250 ml flask. About 150 ml of an anhydrous diethyl ether (petroleum ether) of boiling point of 40-60°C was placed in the flask. 2–5 g of the sample was weighed into a thimble and the thimble was plugged with cotton wool. The thimble with content was placed into the extractor; the ether in the flask was then heated. As the ether vapor reached the condenser through the side arm of the extractor, it condensed to liquid form and dropped back into the sample in the thimble; the other soluble substances were dissolved and carried into solution through the siphon tube back into the flask. Extraction continued for at least 4 h. The thimble was removed and most of the solvent was distilled from the flask into the extractor. The flask was then disconnected and placed in an oven at 65°C for 4 h, cooled in a desiccator and weighed (Oladipo and Jadesimi, 2013). Determination of crude ash
Ash is the inorganic residue obtained by burning off the organic matter of the samples at 400 – 600°C in a muffle furnace for 4 h. 2 g of the sample was weighed into a pre- heated crucible. The crucible was placed in muffle furnace at 400 – 600°C for 4 h or until a whitish-grey ash was obtained; and then was placed in the desiccators and weighed (Oladipo and Jadesimi, 2013)