Reduction of the bioavailability of 20 μg/kg aflatoxin in trout feed containing clay

Abstract

The absorption, metabolism, and excretion of dietary aflatoxin B 1 (AFB 1) by trout given different diets were compared. Fish were fed one of two diets: an AFB 1 contaminated basal diet or 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 low as 0.05 ng AFB 1 were quantified through the use of tritium ( 3 H ) labeled AFB 1 coupled with chloroform/methanol 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 1 found in the feces about 470±20%, compared to control fish not fed bentonite. AFB 1 or metabolite concentrations in urine increased daily for 6 days for both 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 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 μg/kg AFB 1 significantly reduces the amount of AFB 1 absorbed from the digestive system following ingestion of contaminated diets.