Mycotoxin survey 2009: moulds remain a problem for the whole farm-to-fork chain

Unlike primary metabolites, which are essential for fungi growth, mycotoxins are secondary metabolites produced by filamentous fungi (moulds) in the final stages of exponential growth phase. The majority of the known toxigenic species falls into three recognised genera: Aspergillus, Penicillium and Fusarium. Mycotoxin contamination often begins in the field and continues throughout harvest, transportation and storage, depending on the activity and colonisation levels of fungi which are in turn determined by the prevailing environmental conditions and the nutritional components of the food matrix.

In general, fungi are divided in 2 main groups, field fungi and storage fungi, depending if they occur more frequently on the field or after harvest, respectively. However, even if this terminology has been commonly used, conditions for growth of a specific organism can occur in either the field or during storage, especially because even the same fungal genus contains species that differ greatly in their optimum temperature for growth and for their parasitic abilities.

Nonetheless, what is of interest for all participants in the “farm-to-fork” chain is the prevalence and concentration of these substances in feed intended for animal consumption. Since 2005, Biomin GmbH has been carrying out its Mycotoxin Survey Program, in 2009 in collaboration with Romer Labs and Samitec (Brazil). From January until December 2009, a total of 9,030 analyses were carried out for the most important mycotoxins in terms of agriculture and animal production – aflatoxins (Afla), zearalenone (ZON), deoxynivalenol (DON), fumonisins (FUM) and ochratoxin A (OTA). Due to the high limit of detection (125 μg/kg (ppb)) of the Thin Layer Chromatography method for T-2 determination, this toxin was kept out of the survey as its occurrence at levels lower than that may already cause serious problems to animals. In total, 2,660 samples were analysed. Samples tested were diverse, ranging from cereals such as corn, wheat and rice to processing by-products, namely soybean meal, corn gluten meal, dried distillers grains with solubles (DDGS) and other fodder such as straw, silage and finished feed. Origin of the samples varied, namely Asia-Pacific region, Europe, Middle-East and Africa and Americas (North and South America).

Overall results

As can be seen in Figure 1, from all survey samples 33%, 35%, 49%, 56% and 28% tested positive for contamination with Afla, ZON, DON, FUM and OTA, respectively. If compared with data from the previous year (2007/2008), an increase on the occurrence of Afla and OTA can be observed. Figure 2 provides an overview on the distribution of mycotoxins throughout the different regions worldwide. Table 1 gives an overview of the survey results.

Results by commodity

Continuing the trend of past years, corn was shown to be the most extensively and highly contaminated commodity from the survey. With 83% of positive results for FUM, 49% for DON, 45% for Afla, 29% for ZON and 13% for OTA. The highest contamination values found for Afla (6,105 ppb) were detected in this matrix. Soybean and soybean mealsuffered an increase in both prevalence and concentration of mycotoxins when in comparison with data from previous years. In the case of wheat/bran, the most prevalent mycotoxin was still DON, which was present in 57% of tested samples, with an average contamination of 875 ppb. A relatively low number of corn gluten meal samples was tested this year, therefore conclusions must be taken with care. Nevertheless, all tested samples were positive for FUM, 91% were contaminated with ZON, 82% with DON and 55% were positive for Afla and OTA contamination. Except for the latter, contamination levels found in this raw material for all mycotoxins were rather high. In fact, the highest FUM level for the whole survey was found in this ingredient.

The most prevalent mycotoxin found in rice/bran was ZON, with 70% of samples testing positive for this mycotoxin at average levels of 75 ppb. Average contamination levels found for this matrix were somewhat lower when in comparison with the other tested ingredients.

However, despite the relatively low average contamination levels, the co-occurrence and synergistic effects of mycotoxins should not be discarded when using this feedstuff in animal nutrition.

In comparison with the previous survey, fewer DDGS samples were analysed this year. However, very interesting results were found. A higher prevalence of all mycotoxins was observed, except in the case of ZON, for which the percentage of positive results decreased from 90% to 74%. The most prevalent mycotoxin was DON with 94% of positive results.

Finished feed samples represented the highest share of the survey with the highest number of analysed samples. Although still quite impressive contamination levels were found, these were in general reduced in comparison to data from past years. The most prevalent mycotoxin in finished feed was FUM (72%). The sample with the highest contamination of OTA (1,582 ppb) for the whole survey was found in a finished feed sample. A much more substantial amount of straw/silage samples was tested this year, thus enabling a much clearer conclusion. Afla does not really represent a risk in the case of these raw materials. On the other hand, DON and ZON are of greater importance, with 53% and 38% testing positive for these mycotoxins, respectively. Average contamination levels are also rather high (679 and 260 ppb, respectively for DON and ZON).

Barley, a raw material mainly used in Europe was included as a new separated ingredient. The most prevalent mycotoxin in this raw material was DON, present in 44% of the tested samples at average levels of 1319 ppb. The highest ZON and DON concentrations were found in barley samples (8,952 ppb ZON and 11,836 ppb DON, respectively). OTA was not found in any of the analysed samples. Other feed ingredients tested include commodities such as copra meal and cake, palm meal and oil, cassava, fish meal and full fat soy, amongst others. The most prevalent mycotoxin in these matrixes was DON (43% positive), followed by OTA (33%), Afla (28%), ZON (23%) and FUM (14%). Average contamination levels were rather high for all mycotoxins.

Co-occurrence of mycotoxins

As it can be seen in Figure 3 and 4, 75% the analysed samples were contaminated with at least one mycotoxin. In nearly 41% of all analysed samples, more than one mycotoxin was detected. This fact raises the attention to the possibility of interaction between mycotoxins, leading to additive and/or synergistic effects. Such multiple mycotoxin contamination is of great concern in the animal industry. Similar trends were also detected in the different regions except for Europe, where a lower co-occurrence of mycotoxins was observed. However, due to the fact that European samples were most of the times tested only for DON and ZON, it is not possible to withdraw conclusions regarding the co-occurrence of mycotoxins in this region.

Conclusion

The results of this survey program show once again that the presence of mycotoxins is ubiquitous not only in terms of world regions, but also in terms of commodities. On a daily basis animal producers are confronted with the fact that even at low contamination levels, mycotoxins have negative impacts on animal health and performance. On the other hand, animals often undergo extreme performance losses in the field, even at low contamination levels, increased by the co-occurrence of more than one mycotoxin in the feed. The high prevalence and high contamination of non-adsorbable mycotoxins such as deoxynivalenol was attested by this report, thus confirming the importance of the use of a proper Mycotoxin Risk Management tool.