Toxic effects and residue of aflatoxin B1 in tilapia (Oreochromis niloticus × O. aureus) during long-term dietary exposure

As a fish farmed widely in the tropical and subtropical regions where aflatoxin contamination has been generally detected, tilapia has been studied for aflatoxicosis evaluation in Asia. However, relatively short-term aflatoxin B1 (AFB1) exposure in previous studies resulted in some contradictory conclusions. Therefore, this work was designed to investigate the toxic effects and residue of AFB1 in tilapia during a long-term trial of 20 weeks, during which the tilapia obtained more than 1900% weight gain and grew to a commercial size (around 500 g). Tilapia were fed six diets containing different levels of AFB1 (19, 85, 245, 638, 793 and 1641 μg/kg), which were prepared with AFB1-contaminated peanut meal. AFB1-related physiological and toxicological properties in fish were determined during the 20-week period. The results indicated that dietary AFB1 led to aflatoxicosis effects in tilapia in a dose- and duration-dependent manner. No toxic effects of AFB1 were found during the first 10 weeks, but by 20 weeks, the diet with 245 μg AFB1/kg or higher doses reduced the growth and induced hepatic disorder, resulting in decreased lipid content, hepatosomatic index, cytochrome P450 A1 activity, elevated plasma alanine aminotransferase activity and abnormal hepatic morphology, but such dietary AFB1 doses did not affect the survival rate of experimental fish. The AFB1 residue was only detected in liver, in a dose-dependent manner, but not in edible flesh. Taken together, under good culture conditions, tilapia is a rather tolerant species for dietary AFB1 exposure up to 1641 μg/kg diet during 20 weeks. Long-term exposure for more than 15 weeks is necessary to evaluate aflatoxicosis in tilapia. Consuming only tilapia flesh would not increase the risk of exposure to AFB1 for human consumers.