Under certain conditions fungi multiply on cereals, corn, cotton seed and other food materials sometimes producing chemicals called mycotoxins. Fungi require adequate moisture, oxygen and carbohydrates to multiply and temperatures from 10?C to 25?C (50?F to 77?F). Multiplication may still take place however outside these ranges and crops that are already diseased are more likely to succumb to fungal infection. The presence of fungi including recognised toxic species however does not necessarily mean that the toxins are present. Each requires precisely the right substrate and environmental conditions to produce toxins. The common fungi causing disease (mycotoxicosis) in the pig include species of Fusarium, Aspergillus and Penicillium, but because of the variable requirements for growth and toxin production, particular species tend to predominate in certain geographical areas. Toxins are not destroyed by heating but modern treatments used in the processing of animal feeds such as temperature and pressure may reduce the actual fungal load.

Fusarium species require high levels of moisture and relative humidity (>88%) for multiplication and toxin production whereas Aspergillus and Penicillium multiply at lower levels.

Aflatoxins and some of the ochratoxins are immuno-suppressive and can enhance effects of generalised disease.


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