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Preliminary Assessment of Heavy Metal Concentrations in Selected Fish Feed Ingredients in Nigeria

Adeniji CA and Okedeyi OO

Dearth of information exist on the heavy metal concentration (HM) of local fish feed ingredients in Nigeria, thus preliminary investigation on the concentration of lead (Pb), cadmium (Cd) (toxic heavy metals), copper (Cu), zinc (Zn) and chromium (Cr) (essential trace metals) present in some selected feed ingredients. The two toxic metals; lead and cadmium were found in fishmeal at the concentration of 0.30 mg/kg each. Cd content in soybean meal, groundnut cake, maize and soybean cake were 0.01, 0.3, 0.4 and 0.5 mg/kg respectively. Chromium was not detected in soybean cake and maize. Soybean meal and fishmeal had the same chromium content of 0.20 mg/kg, while highest concentration of chromium (1.00 mg/kg) was found in groundnut cake. Maize had the highest copper content of 1.00 mg/kg, groundnut cake 0.40 mg/kg, followed by 0.21 mg/kg in soybean cake and lowest concentration of 0.20 mg/kg was found in both soybean meal and maize. Fish meal had the highest zinc content of 1.70 mg/kg, followed by 0.91 mg/kg in maize and 0.90 mg found in soybean cake and meal, while groundnut cake had the least zinc content of 0.70 mg/kg. The values of the heavy metal content of the selected feed ingredients are far below fish’s requirement for essential metals (copper, zinc and chromium). The results seem to buttress the need to fortify fish’s feed with these essential metals from other sources. Otherwise fish and human the ultimate consumer may be predisposed to assimilation and bioaccumulation of cadmium and lead which are chemical analogues of zinc; especially with the current use of exogenous enzymes which may improve nutrient bioavailability.