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Ursula Hofstetter, DI (MSc), has studied at the University of Natural Resources and Applied Life Sciences in Vienna, Austria and at the Department of Agricultural Sciences at the University of Bologna in Italy.

She joined Biomin in 2002 and worked for two years as Area Sales Manager UK, Ireland and Belgium. Between 2004 and 2007, she was product manager for the Mycofix® Product Line. Since the beginning of this year, she was appointed as Director of the company’s strategic business unit called "Mycotoxin Deactivation".

She is a member of the German Association for Mycotoxins Research and the International Society for Mycotoxicology.

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Title: Dealing with Mycotoxins in Animal Feed

Numerous crops are susceptible to fungal invasion and in turn might be contaminated with mycotoxins, originating from the secondary metabolism of moulds. Despite extensive efforts to prevent mycotoxin formation during plant growth or storage it is estimated that still 25 % of the world’s crop production is contaminated to some extent.

Mycotoxins in grain involve a great deal of problems in food/feed- and animal-production. They can cause a wide variety of negative impacts on animal health, depending among various other factors on their nature and concentration. Especially chronic mycotoxicoses leading to unspecific symptoms often entail serious economic losses. Once produced it is very difficult to get rid of mycotoxins or even to reduce the contamination level as these toxins possess high physical and chemical stability. Therefore suitably new strategies had to be found in order to successfully counteract these undesired compounds.

Costs and limitations of physical and chemical treatments of feed prompted the search for other solutions concerning the mycotoxin hazard. Consequently, techniques based on deactivation of mycotoxins directly in the gastrointestinal tract of animals were investigated. Up to now, the most widespread method in this field is the addition of chemisorbents with the capacity to tightly bind and immobilize mycotoxins in the gastrointestinal tract of animals, resulting in a major reduction of toxin bio-availability. In several studies, hydrated sodium calcium aluminosilicates (HSCAS) have proven to be the most promising adsorbents.

However, while good and scientifically explained results were obtained for counteracting aflatoxins (Ramos and Hernandez, 1996), adsorption of other mycotoxins was limited (e.g. zearalenone, ochratoxin A) or even failed (e.g. trichothecenes, like deoxynivalenol) under field conditions (Friend et al., 1984; Kubena et al., 1990; Huff et al., 1991). In the case of less- and non-adsorbable mycotoxins new paths have to be treaded.

 

However, enzymatic or microbial degradation of mycotoxins ("biotransformation") has already been a subject of research for more than 30 years (Kollarczik et al., 1994; He at al., 1992; Yoshizawa et al., 1983). A great deal of respective literature is available concerning the biotransformation of trichothecenes, as these mycotoxins actually belong to the agriculturally most important toxins worldwide. By now it is well known that the 12,13-epoxide ring of trichothecenes is able react with DNA and consequently impairs protein biosynthesis in animals and that a reductive de-epoxidation caused by specific enzymes (de-epoxidases) entails a significant loss of toxicity. However, Binder et al. (2000) were the first to develop a trichothecene-deactivating feed additive based on live microbes and enzymes. Toxicity of zearalenone is based on its structural similarity to the female hormone estrogen. Like estrogen, ZEA can be bound to the estrogen-receptor, finally resulting in characteristic symptoms called "hyperestrogenism" (= fertility problems). Hydrolysis of the toxin’s ester group (i.e. opening of the lacton ring) by means of specific enzymes (esterases, lactonases) removes the structural similarity to estrogen, resulting in non-toxic and therefore harmless metabolites

 

Conclusions
For many reasons it is not possible to totally avoid mycotoxin-contaminations in feed. A lot of research has been done to adsorb or deactivate these toxins in the intestinal tract of animals with products that are directly mixed into the feed. It turned out that some mycotoxins, like trichothecenes, cannot be adsorbed sufficiently. Thus, enzymatic biotransformation to metabolites without pathogenic activity is the only way to avoid their negative effects on animals. Summarizing it can be said that only the combination of different strategies - adsorption and biotransformation – will finally lead to success.