Q&A on mycotoxins

The topic "Mycotoxins" and all related subjects can be very complicated and often lead to unanswered questions. www.mycotoxins.info attempts to cover these issues comprehensively and offers useful information to everybody who might be confronted with problems that can be attributed to mycotoxins. Nevertheless, this website cannot possibly answer all the questions that might surface while dealing with this subject. This is mainly due to the fact that the question at hand might be too specific to answer it adequately in the context of this portal.

This is why the section "Q&A on mycotoxins" was established. It provides a list of frequently asked questions.
 


Questions:

What are masked mycotoxins?
Do safety levels for mycotoxins exist?
When do moulds produce mycotoxins?
How many mycotoxins have already been discovered?
Which feed/food ingredients are mostly affected by mycotoxins?
How can feed be analyzed for mycotoxins?
Are all animals sensitive to mycotoxins?


 

What are masked mycotoxins?
As the fungi are growing mainly on plants and are producing mycotoxins at the same time, they are toxic also for plants. Plants have an ability to protect themselves against mycotoxins by binding a certain molecule (eg. glucose, sulphur…) to the molecule of mycotoxin.
The molecule of an original mycotoxin is changed and loses its toxicity.
Masked mycotoxins (because of their changed chemical structure) cannot be detected by conventional analytical methods (HPLC, ELISA). During digestion the intestinal enzymes cleave the masked mycotoxins and the parent mycotoxins are released. After release from the bound mycotoxins can be absorbed into the blood circulation and become again toxic for the animal.

Do safety levels for mycotoxins exist?
While the question of safe mycotoxin levels is a valid and vital one, it cannot easily be answered. Perhaps the shortest answer is "there is only one safe mycotoxin level and that is zero", as according to Hamilton, all levels of mycotoxins can be considered as unsafe. Even small amounts can have a detrimental effect on immune system and metabolism, thus posing a continuous threat to human and animal health. Subsequently, sub-clinical levels of mycotoxins which are commonly found, almost always have an observable influence on economic success in animal production. However, outstanding toxicological and survey analytical data as well as insufficient methods of mycotoxin analysis generally influence the establishment of safe levels or limits for certain mycotoxins. Moreover it has always to be kept in mind that heat stress, marginal nutrient plane, crowding, disease exposure, the presence of more than one mycotoxin (i.e. synergistic effects) and drug interactions, as well as many other factors, can increase animals' susceptibility to certain mycotoxins. Nevertheless, different countries have enforced different thresholds to limit the passage of mycotoxins along the food chain.

When do moulds produce mycotoxins?
Worldwide 30 to 40% of all existing fungi might be able to form mycotoxins under appropriate conditions either on the growing field plant ("field or plant pathogenic fungi") or later during storage ("storage or saprophytic fungi"). Subsequently these undesired compounds might occur in food and feed, thus endanger human or animal health and cause severe economic losses. Mould growth and toxin production are generally influenced by a variety of plant and environmental factors, including substrate characteristics (e.g. composition, pH, water activity, oxygen content), possible competitive actions (e.g. associated growth of other fungi or microbes) and climatic conditions (e.g. temperature, atmospheric humidity). In warm (tropical and subtropical) regions for instance aflatoxins are of major concern, while fusariotoxins, such as zearalenone or trichothecenes, mainly occur in more moderate regions. However, storage fungi including Aspergillus and Penicillium sp., may grow and produce mycotoxins even when moisture content ranges from 14 to 18% and at temperatures that vary from 10 to 50°C. Moreover, stress factors such as drought, poor fertilization, high crop densities, weed competition, insect or mechanical damage can weaken the plant's natural defense and thus promote colonization by mycotoxin-producing fungi as well as toxin-formation.

How many mycotoxins have already been discovered?
Currently there are more than 400 different mycotoxins documented with new ones still being identified. However, the most important ones from the point of view of animal health and productivity are deoxynivalenol, T-2 toxin, zearalenone, aflatoxin B1, ochratoxin A and fumonisins.

Which feed/food ingredients are mostly affected by mycotoxins?
Occurrence of mycotoxins in food and animal feed often exhibits a geographic pattern, as for example Aspergillus species meet optimal conditions in tropical and subtropical regions, whereas Fusarium and Penicillium species are adapted to the moderate climate of North America and Europe. However, worldwide trade with food and feed commodities resulted in a wide distribution of contaminated material. Generally it has to be said, that every grain can be affected by mycotoxins. The toxins can accumulate in maturing corn, wheat, soybeans, sorghum, peanuts and other food and feed crops in the field, during transportation or improper storage. Moreover, in animals consuming contaminated feed, mycotoxins can deposit in different organs and subsequently also affect food of animal origin (e.g. meat, eggs, milk, milk products).

How can feed be analyzed for mycotoxins?
Actually there are different methods to analyze feed for mycotoxins, including
- ELISA (enzyme linked immunosorbent assay),
- TLC (thin layer chromatography),
- GC (gas chromatography) and
- HPLC (high performance liquid chromatography).
The main application of ELISA is as rapid screening test to monitor the presence or absence of a particular mycotoxin. The major drawback of this method is its limitation to semi-quantitative test results. Similar to ELISA, thin layer chromatography (TLC) is only a semi-quantitative method. In order to obtain accurate information with regard to mycotoxin concentrations in feedstuffs quantitative methods such as GC and HPLC, respectively, are inevitable.

Are all animals sensitive to mycotoxins?
Generally it can be said that all animal species can be affected by mycotoxins. However, sensitivity varies with numerous factors including among others the animal's sex, age, breed, physiological status and nutritional standing, the kind(s) of mycotoxin(s) consumed, intake level, duration of exposure, farm management (hygiene, temperature, air conditioning, humidity, production density, etc.) and possible infections. Among the most sensitive animals are pigs and rabbits as well as all reproductive and young animals of all species. Although monogastric animals are known to be more sensitive to mycotoxins than ruminants, high producing cows and calves are demonstrably affected.


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