Nutritionist > Pig

What are mycotoxins?
The word mycotoxin stems from the Greek word "mykes", meaning mould, and "toxicum" meaning poison. Human cases of ergotism or St. Anthony's Fire have been described in Europe since the Middle Ages and are now known to be caused by alkaloids produced in rye by the mould Claviceps purpurea. In 1960, an outbreak of Turkey X disease in England and the subsequent discovery of the aflatoxins stimulated great interest in the field of mycotoxin research (Bullerman, 1979). Since then many more mycotoxins, such as trichothecenes, zearalenone, ochratoxins and fumonisins have been discovered.

Mycotoxins are toxic secondary metabolites produced by fungi growing on crops in the field, during handling and in storage. They enter the animal production system via feed (concentrate, silage or forage) or via bedding. Mycotoxins negatively affect animal performance, animal health and product quality. Thus mycotoxin control is crucial for production economics, animal welfare, product quality and food safety reasons.

Mycotoxins are chemically different representing a variety of chemical families and range in molecular weight from about 200 to 500 kD. There are hundreds of known mycotoxins, but few have been extensively researched and fewer still have good methods of available analysis. Mycotoxins vary greatly in their severity.

Mycotoxins exert their effects through four primary mechanisms:

• Intake reduction or feed refusal
• Alteration in nutrient content of feed in terms of nutrient absorption and metabolism
• Effects on the endocrine and exocrine systems
• Suppression of the immune system

These effects often lead to rather unspecific symptoms, which can also be caused by many other factors making if difficult to properly diagnose mycotoxin problems. General symptoms (reduced performance, impaired immunity) are seen when dealing with moderate mycotoxin levels, while symptoms caused by higher mycotoxin levels are often more specific. Further complications in mycotoxicosis diagnoses can be caused by secondary symptoms resulting from opportunistic disease related to the suppression of the immune system following mycotoxin exposure.

In order to effectively identify mycotoxicosis, experience with mycotoxin-affected animals is important. This experience, combined with adequate feed and tissue analyses, provide the basis for the most accurate diagnosis of mycotoxicosis.

Moulds grow by producing long filaments called hyphae, which are important for the survival and dispersal of fungi. The hyphal network is responsible for cementing kernels together, which in stored grain or feed can result in clumps of grain that cannot be separated. Grain-mould fungi also produce spores (conidia) capable of aerial dispersal in the field as well as within a grain storage bin. It is usually masses of these spores that give the mould a characteristic colour. Spores can lay dormant for months or years until the proper conditions for fungal development are available.

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