Evaluation of Chemical Parameters and Heavy Metals in Fish Feed Ingredients Sourced in South West Nigeria

Aquaculture expansion in South West Nigeria depends on affordable and nutritionally adequate fish feed, but the quality of locally sourced ingredients including fish meal, soybean meal, and maize is rarely systematically evaluated for chemical composition, contaminants, or heavy metal content before use. This study evaluated the chemical composition and heavy metal content of six commonly used fish feed ingredients, namely fishmeal, soybean meal, groundnut cake, maize, blood meal, and wheat bran, collected from feed ingredient dealers in Lagos, Ogun, and Oyo States. Proximate analysis, acid-insoluble ash, and heavy metal determination were conducted. Total aflatoxin content was measured using ELISA. Fishmeal samples varied widely in crude protein content, ranging from 52 to 71 percent, with 35 percent of samples below the specification of 62 percent. Soybean meal protein varied from 38 to 46 percent. Heavy metals lead and cadmium were detected in fishmeal at levels up to 3.8 mg/kg and 0.42 mg/kg respectively, with some samples exceeding EU maximum levels for aquafeed ingredients. Aflatoxin contamination above 20 micrograms per kilogram was found in 40 percent of maize and groundnut cake samples, presenting a risk of immunosuppression and growth reduction in cultured fish. These results underscore the need for mandatory chemical quality certification of fish feed ingredients and recommend the development of a quality assurance framework for the South West Nigerian aquaculture feed supply chain.

Keywords: fish feed ingredients, heavy metals, aflatoxin, aquaculture, South West Nigeria