Dietary influences on excretory pathways and tissue residues of zearalenone and zearalenols in the rat

Invited review: Diagnosis of zearalenone (ZEN) exposure of farm animals and transfer of its residues into edible tissues (carry over)

The aim of the review was to evaluate the opportunities for diagnosing the zearalenone (ZEN) exposure and intoxication of farm animals by analyzing biological specimens for ZEN residue levels. Metabolism is discussed to be important when evaluating species-specific consequences for the overall toxicity of ZEN. Besides these toxicological facts, analytics of ZEN residues in various animal-derived matrices requires sensitive, matrix-adapted multi-methods with low limits of quantification, which is more challenging than the ZEN analysis in feed. Based on dose-response experiments with farm animals, the principle usability of various specimens as bio-indicators for ZEN exposure is discussed with regard to individual variation and practicability for the veterinary practitioner. ZEN residue analysis in biological samples does not only enable evaluation of ZEN exposure but also allows the risk for the consumer arising from contaminated foodstuffs of animal origin to be assessed. It was compiled from literature that the tolerable daily intake of 0.25 μg ZEN/kg body weight and day is exploited to approximately 8%, when a daily basket of animal foodstuffs and associated carry over factors are assumed at reported ZEN contamination levels of complete feed.

Recent advances on the use of adsorbent materials for detoxification ofFusariummycotoxins

The extensive use of adsorbents in the livestock industry has led to the introduction of a wide range of new products on the market, most of them claiming high in vitro mycotoxin adsorption capacity. However, adsorbents that may appear effective in vitro do not necessarily retain their efficacy when tested in vivo. Studies performed in our laboratory during the past few years aiming to evaluate the efficacy of various adsorbent materials in binding Fusarium mycotoxins are reported. Adsorption experiments were performed in in vitro screening tests for Fusarium mycotoxins at different pHs; by in vivo tests using the increase of the sphinganine to sphingosine ratio in rat urine and tissues as a biomarker of fumonisin exposure; and by a dynamic, computer-controlled, gastrointestinal model simulating the gastrointestinal tract of healthy pigs. Most of the commercially available mycotoxin-binders failed in sequestering in vitro Fusarium mycotoxins. Only for a small number of adsorbent materials was the ability to bind more than one mycotoxin demonstrated. Cholestyramine was proven to be an effective binder for fumonisins and zearalenone in vitro, which was confirmed for zearalenone in experiments using a dynamic gastrointestinal model and for fumonisins in in vivo experiments. No adsorbent materials, with the exception of activated carbon, showed relevant ability in binding deoxynivalenol and nivalenol. The in vitro efficacy of activated carbon toward fumonisins was not confirmed in vivo by the biomarker assay. The dynamic gastrointestinal model was a reliable tool to study the effectiveness of adsorbent materials in reducing the bioaccessibility of Fusarium mycotoxins, as an alternative to the more difficult and time-consuming studies with domestic livestock.

Effect of diet on T-2 toxicosis

T-2 toxin is an emetic trichothecene mycotoxin produced by Fusarium molds. This compound causes feed refusal, emesis and lesions in the gastrointestinal tract of livestock, poultry and man. Studies in our laboratory have indicated that the feeding of high fibre diets, non-nutritive mineral additives and high fat diets can largely overcome feed refusal caused when T-2 toxin is fed to rats. Subsequent experiments were designed to determine the mechanism by which such diets exert this effect. Rats were fed for two weeks diets containing varying levels of alfalfa meal, bentonite or corn oil in a casein-based semi-purified diet. Rats were then orally dosed with [3H] T-2 toxin and urine and feces were collected for 21 hours after which all animals were killed and tissues excised. Diet had no significant effect on the fraction dose of 3H excreted in the urine. Significant increases in fecal excretion of 3H were seen, however, with all test diets. Only high fat diets reduced hepatic residues of 3H while alfalfa had a similar effect in kidney and both alfalfa and bentonite lowered muscle residues. It was concluded that such dietary treatments overcome T-2 toxicosis mainly by promoting fecal excretion of toxin thereby reducing absorption and biological half-life.