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Mycotoxins: Threshold no longer the only barometer of risk

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By Jane Byrne

Last updated on 12-Jan-2017 at 13:57 GMT2017-01-12T13:57:36Z

© istock/luplupme
© istock/luplupme

The co-contamination of feedstuffs with multiple mycotoxins is the rule and not the exception, according to the lead author on a new paper, published in Toxins.

The researchers, led by Dr Paula Kovalsky, product manager, Biomin, and including the analytical team at IFA Tulln, said they evaluated 57 mycotoxins and secondary metabolites from regulated, masked and emerging compounds in 1,113 samples from three different matrices - finished feed, maize and maize silage - for the years 2012–2015.

The study found:

  • A high occurrence of masked and emerging compounds in finished feed samples from Central Europe.
  • Typically, over 50% of samples contained three or more (out of six) regulated toxins or toxins with guidance levels, both (two out of two) masked toxins (DON-3-glucoside and ZEN-14-sulfate) and three or more (out of five) emerging toxins.
  • Deoxynivalenol (DON) is usually well correlated with masked mycotoxin, DON-3-glucoside, as is ZEN with ZEN-14-sulfate.

Rethink needed on global contamination estimates?

Moreover, the researchers also concluded that actual mycotoxin occurrence is likely three times higher than the estimates of the Food and Agriculture Organization of the UN (FAO). 

“Our findings, along with the results of studies published by others, indicate considerably more than the FAO suggested figure of 25% of global agricultural commodities are contaminated with mycotoxins. In fact, over 80% of the agricultural commodities could be affected globally,” said Kovalsky. 

But she said it needs to be stressed that those FAO figures were published 15 years ago. 

Still a lot of unknowns about masked and emerging mycotoxins: researchers © istock/endopack

The researchers said they also saw large increases in annual medians for DON, zearalenone (ZEN) and fumonisins in Europe, the region that provided the largest data set for the survey.

And they found regional variation in mycotoxin occurrence, even where climatic conditions were similar. “We saw an increase in DON in Austria compared to Germany. Further research is needed to determine if this variation is due to meteorological factors or as a result of the type of cultivar used. Studies have shown, for example, that not all cultivars have the same level of resistance and susceptibility to different fungi,” said Kovalsky. 

Threshold no longer the only barometer of risk….

When asked whether only mycotoxin contamination at rates higher than threshold levels set by regulators should be the main consideration at play, certainly for feed producers and livestock farmers, she told us:

Mycotoxins rarely contaminate alone. Furthermore, we, and other researchers, have seen that, even at low concentrations, below the guidance values, the synergistic effect of co-occurring mycotoxins can have a negative impact on the animal.”

In a meta-analysis of studies evaluating the toxicological impact of co-contamination of feed [and food] by multiple mycotoxins, Isabelle Oswald, a researcher based at INRA in Toulouse, observed:

“The toxicity of mycotoxins mixtures cannot always be predicted based upon their individual toxicities. It can be antagonistic, additive or synergistic and increase the impact of each mycotoxin.”

And other animal scientists have found that even if mycotoxin contamination levels in pig feedstuffs are usually not high enough to cause an overt disease, they may result in economical loss through changes in growth, production and immunosuppression (Bryden, 2012Oswald et al., 2005  and Wild and Gong, 2010 ).

Masked and emerging mycotoxins

Kovalsky stressed that masked and emerging mycotoxins present many challenges for industry, the scientific community and authorities.

Masked mycotoxins like DON-3-glucoside are not detected by conventional techniques, but are ‘cleaved’ in an animal’s digestive tract, releasing DON that can then disrupt gut integrity, for example, she said.  

Emerging mycotoxins are unregulated, and, often, their effects in animals are less well understood, added Kovalsky. They are a group of chemically diverse mycotoxins for which to date no regulations exist.

She said analysis using advanced liquid chromatography tandem mass spectrometry (LC–MS/MS) is enabling greater insight into these newly discovered metabolites including aflatoxin precursors, ergot alkaloids, enniatins, beauvericin (BEA) and moniliformin (MON).

“A big question is what, if any, negative effects emerging mycotoxins have on animals. This is a new area of risk assessment for toxicologists and authorities such as the European Food Safety Authority (EFSA) are increasingly taking account of these compounds in risk evaluations,” said Kovalsky.

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