Introduction
Modified mycotoxins are derivatives of mycotoxins produced by fungi or formed through the metabolism of infected plants or animals as part of their defence mechanisms. The lack of data on these compounds limits the understanding of their toxicity, which may be equal to, lower than, or higher than that of the parent mycotoxin. Therefore, it is important to consider that exposure to these metabolites may result in significant alterations in poultry health and performance.
Modified mycotoxins of zearalenone
In the case of zearalenone (ZEN), the predominant metabolite in broiler chickens and laying hens is typically β-zearalenol (β-ZEL), whereas in turkeys it is α-zearalenol (α-ZEL). Glucuronidation represents the main conjugation pathway.
In poultry, exposure assessments indicate that between 93% and 100% of documented exposure is associated exclusively with the parent compound ZEN. This largely reflects the limited availability of data on the modified forms of this mycotoxin, including α-zearalanol (α-ZAL), β-zearalanol (β-ZAL), zearalanone (ZAN), α-ZEL, and β-ZEL. Consequently, the contribution of these modified forms to overall exposure in poultry remains insufficiently characterised.
EFSA (2017) concluded that the risk of ZEN and its modified forms adversely affecting poultry health is extremely low. This conclusion is supported by the high tolerance of poultry to this mycotoxin, as reflected in elevated NOAELs (no-observed-adverse-effect levels), and by the fact that typical poultry diets generally do not contain high concentrations of ZEN.
Regarding interspecies sensitivity, turkeys appear more tolerant than chickens, with a NOAEL of 9,100 µg/kg body weight, compared with 7,500 µg/kg body weight in chickens. This difference is based on observed effects, including lymphocyte reduction and ventricular inflammation.
ZEN and its modified forms exhibit estrogenic activity, meaning they can mimic the effects of endogenous female sex hormones, a property closely linked to their toxicological relevance. However, this activity differs among the various compounds. In descending order of estrogenic potency, the ranking is as follows:
α-ZEL > α-ZAL > ZEN = ZAN = β-ZAL > β-ZEL.
These differences indicate that certain metabolites may display greater biological activity than the parent mycotoxin.
Modified mycotoxins of deoxynivalenol
Deoxynivalenol (DON) can be transformed into various compounds, such as DON-3-glucoside (DON-3-G), which is its primary metabolite in plants. Unlike pigs, chickens are unable to convert DON-3-G back into DON, which may reduce its toxicity in this species. However, in chickens, 3-acetyl-DON (3-Ac-DON) has been shown to be almost completely converted into DON, whereas 15-acetyl-DON (15-Ac-DON) undergoes only partial conversion. Moreover, since these compounds share a common mechanism of action at the ribosomal level, they are expected to exhibit comparable intestinal toxicity.
In terms of interspecies sensitivity, turkeys appear to be more tolerant to DON than broiler chickens, laying hens, and ducks, based on reported NOAELs.
Alizadeh et al. (2016) evaluated the cytotoxicity and effects on intestinal permeability of DON and several of its metabolites using Caco-2 cells, a widely accepted in vitro model of the human intestinal epithelium. The results showed that 3-Ac-DON exhibits overall toxicity comparable to DON, although with lower cytotoxic effects and a lesser impact on intestinal barrier function. By contrast, 15-Ac-DON was slightly more toxic than DON. Neither DON-3-G nor de-epoxy-DON (DOM-1) produced measurable adverse effects on intestinal integrity.
Regarding poultry, DON-3-sulfate (DON-3S) is one of the main excretion metabolites. Jurisic et al. (2019) studied its potential transfer to eggs and concluded that there is no significant risk to public health, even if DON-3S, which is not toxic by itself, were to be hydrolyzed in the consumer’s intestine, releasing active DON.
Conclusion
Thus, it is necessary to deepen the research on modified mycotoxins derived from compounds such as ZEN or DON, among others, due to their potential negative impact on the intestinal, immunological, and hepatic health of poultry. These modified forms can significantly alter various physiological and productive parameters, compromising zootechnical performance and increasing susceptibility to diseases.
