Masked mycotoxins can escape detection by routine analytical methods, leading to an underestimation of the degree of contamination. Metabolites of DON, one of the most prevalent toxins, can create increased risks in the digestive tracts of animals.
Mycotoxins are toxic fungal metabolites that can contaminate a wide array of crops. The most frequently occurring mycotoxins with well-known toxic effects are:
One of the most important mycotoxin producing fungi are those of the Fusarium genus, which typically produce mycotoxins on the crops while still in the field. Fusarium fungi can produce several toxins of which the trichothecenes (including deoxynivalenol (DON) and T-2 toxin), FUM and ZEA are the most important based on occurrence and toxicity. Of these, DON is the most prevalent. It is typically found in wheat, barley, corn, rye, oats, and thus also in compound feeds of production animals.
The toxic effects induced by DON are well characterised in most production animals, with pigs being the most susceptible, for which the lowest guidance value of 0.9 ppm in complete feed was established.
Occasionally, manifested clinical symptoms due to intake of mycotoxin-contaminated feed are more serious than expected based on analytical results. This has led to the discovery of masked mycotoxins which escape detection by routine analytical methods. Consequently, this can lead to an underestimation of the degree of contamination upon analysis.
Metabolites of DON include 3-acetyl-DON (3ADON), 15-acetyl DON (15ADON) and deoxynivalenol-3-β-D-glucoside (DON3G). These metabolites can have a direct toxic effect, or can be hydrolysed to DON in the digestive tract of animals, resulting in higher exposure levels to DON. At this moment, there are no directives, regulations nor recommendations in food or feed taking these derivatives of DON into account.
An overview of the occurrence of DON and its metabolites as shown in Table 1 originates from 13 reports published between 2010 and 2014 on wheat, maize, barley, oat and rye. As can be seen, the level of incidence is not negligible and thus their presence should not be ignored.
Following oral intake of DON and its acetylated metabolites, the intestinal mucosa will be exposed first. This barrier to foreign antigens is composed of intestinal epithelial cells which are interconnected by tight junctions. It was demonstrated that DON and its metabolites are able to increase the permeability of the intestinal epithelial layer by decreasing the expression of tight junction proteins. Further, a reduction in cell proliferation was demonstrated. Together, these actions increase the animal’s susceptibility to pathogens. Another point of concern is the co-contamination of DON with other mycotoxins and metabolites of DON, and their potentially synergistic effects.
Trichothecenes are rapidly absorbed and excreted without accumulation in any tissue, and only traces of the toxins are found 24 hours after oral exposure. The main route of excretion is the urine, and only a small fraction is excreted in the faeces. Once ingested, in pigs 3ADON and 15ADON are rapidly hydrolysed to DON (1) and detected in blood shortly after oral exposure to these toxins (2), see Figure 1. Most of the ingested (A)DON is absorbed before microbial de-epoxydation to the non-toxic metabolite (A)DOM-1 can effectively take place further in the gut.