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From a global perspective, three classes of Fusarium mycotoxins may be considered to be of particular importance in animal health and productivity. Within the trichothecene group, deoxynivalenol (DON) is widely associated with feed rejection in pigs, while T-2 toxin can precipitate reproductive disturbances in sows. Another group comprising zearalenone (ZEN) and its derivatives is endowed with oestrogenic properties. The third category includes the fumonisins which have been linked with specific toxicity syndromes such as equine leukoencephalomalacia (ELEM) and porcine pulmonary oedema. Many toxigenic species of Fusarium are also common pathogens of cereal plants, causing diseases such as head blight of wheat and barley and ear rot of maize. Consequently, when cereal plants are infected with these fungi, there is a risk that grain may become contaminated with Fusarium mycotoxins and that these may subsequently be transferred to compound feeds. The surveillance of grain and animal feed for the occurrence of Fusarium mycotoxins continues to attract worldwide attention and has been the subject of extensive investigations over recent years. For example, high incidence rates of contamination with DON and another trichothecene, nivalenol (NIV), have been reported in maize samples in New Zealand. In Poland, unacceptably high values (up to 927 mg/kg) for DON were recorded for maize grain and cobs. Potentially harmful levels of DON (up to 40 mg/kg) were also observed in wheat produced in Germany, Poland, Japan, New Zealand, USA, Canada and Argentina. Samples of barley grain in Norway, Japan and USA were found with DON levels of up to 71 mg/kg. In the Norwegian study oat samples were also contaminated with DON at levels ranging from 7 to 62 mg/kg grain. Abnormally high concentrations of both NIV and ZEN have been observed in some Japanese barley samples (up to 26 and 15 mg/kg, respectively), and in maize produced in New Zealand (up to 7 and 10.5 mg/kg, respectively). Other trichothecenes such as 3-acetyl DON, diacetyoxyscirpenol (DAS), T-2 toxin and HT-2 toxin have also been found in cereals and animal feed in both temperate and tropical countries. In Uruguay all samples of maize-based animal feeds tested were positive for fumonisin B1 (FB1). However, highest FB1 values were observed in South Africa for compound feed (11 000 μg/kg), and in Thailand and China for maize (18 800 and 25 970 μg/kg, respectively). In a study of Argentinian maize, FB2 was the major fumonisin at values of up to 11 300 μg/kg. An alarming feature of several surveys is that in the tropics in particular, several Fusarium mycotoxins may co-occur with each other and with aflatoxin B1, an Aspergillus compound sharing carcinogenic properties with fumonisins. It is concluded that, although sample size has been small in a number of surveys, there is nevertheless unequivocal evidence of global contamination of cereal grains and animal feed with several trichothecenes, ZEN and fumonisins. Furthermore, it is clear that legislation for the control of these mycotoxins in animal feed is now overdue and that further work is required to exploit cereal genotypes that are resistant to diseases caused by toxigenic Fusarium phytopathogens. |
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