Reduction of the bioavailability of 20 mgrkg aflatoxin in trout feed containing clay

Ž . The absorption, metabolism, and excretion of dietary aflatoxin B AFB by trout given 1 1 different diets were compared. Fish were fed one of two diets: an AFB contaminated basal diet or 1 the contaminated basal diet with 2% sodium bentonite. Urine, feces, and gill excretions were collected and analyzed separately over a 7-day test period. On completion of the feeding trials, the fish were euthanized for chemical analysis of body fluids and major organs. Total organ loads as Ž . low as 0.05 ng AFB were quantified through the use of tritium H labeled AFB coupled with 1 1 chloroformrmethanol extraction, oxygen bomb combustion and liquid scintillation counting of samples. Results demonstrated that 2% dietary bentonite supplementation blocked intestinal absorption of dietary aflatoxin, reducing liver and kidney aflatoxin loads by at least 80"10%, and increasing the amount of AFB found in the feces about 470"20%, compared to control fish 1 not fed bentonite. AFB or metabolite concentrations in urine increased daily for 6 days for both 1 groups, but were always significantly lower in the bentonite-fed group. On average, insoluble aflatoxin metabolites accounted for 40%–60% of the total aflatoxin load in tissues, indicating a Ž . high percentage conversion to an adduct that binds to protein or other materials in the tissues and is not extracted by solvents. All data indicate that 2% bentonite contained in trout diets contaminated with 20 mgrkg AFB significantly reduces the amount of AFB absorbed from the 1 1 digestive system following ingestion of contaminated diets. q 2000 Elsevier Science B.V. All rights reserved.