Mycotoxins are harmful metabolites produced by molds (fungi). They can originate pre-harvest due to adverse climatic conditions and can continue to be formed postharvest under suboptimal storage conditions. The most significant mold species producing mycotoxins pre-harvest include Aspergillus and Fusarium fungi while Penicillium and also Aspergillus fungi are more significant with respect to contamination in storage. While environmental conditions in storage of feedstuffs can be controlled, climatic conditions pre-harvest can present a significant challenge to producers.
It would appear that the frequency of poultry productivity challenges arising from mycotoxin-contaminated feeds is increasing. This is likely due, in part, to extreme weather conditions in crop growing areas globally. The United Nations Intergovernmental Panel On Climate Change recently reported that global warming and extreme weather conditions are becoming more frequent. High moisture conditions arising from excess rainfall and flooding pre-harvest are key factors in promoting mold growth and potential mycotoxin contamination. Drought conditions can also increase the chances of mycotoxin contamination, however, as shriveling and cracking of grain kernels can allow fungal spores to breach fibrous mechanical barriers and to grow on starchy endosperm layers. The spectrum of mycotoxins produced under hot, dry, drought conditions (eg aflatoxin, fumonisin), however, usually differs from those produced under wet, cool conditions (eg. deoxynivalenol (DON), zearalenone, fusaric acid).