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John Maltman, Manitoba Agriculture and Food, Dugald
Vomitoxin contamination of cereals continues to be a problem for livestock producers. With the proper moisture and temperature conditions at flowering time, the fusarium fungi responsible for producing deoxynivalenone (DON) can get established on the plant. This fungi doesn't always produce toxin even though it is present on the grain kernel. Generally high levels of humidity will allow the mould to grow. If grain is stored tough and fusarium is present, the DON levels will continue to rise in storage. It is important to store grain dry.
Research has been directed at resolving the vomitoxin problem on several fronts with some success. Currently three methods have been researched which include physical, chemical and genetic approaches.
Long term, our plant breeders will breed in resistance to this mould. In the short term, things like heat treatment and additives have been tried in order to reduce the impact of DON, but have met with limited success. Another category of mycotoxins called aflatoxins are virtually eliminated by binders. However, vomitoxin is very poorly bound so the search for an additive to bind it continues.
Heat treatments have only been able to reduce vomitoxins by 20% or so and is somewhat inconsistent. Physical treatment is showing some promising results.
Based on work by Dr. Trenholm from Agriculture Canada, dehulling showed that it could be as high as 100% successful in removing DON from contaminated barley. If the fungi had not penetrated into the endosperm, this process was successful. Improper storage or ideal mould growing conditions can allow the mould to contaminate the endosperm which reduces the effectiveness of dehulling.
Tests done by Manitoba Agriculture and Food have shown that samples dehulled in the lab had the DON removed from the kernel with the hull. Early results from on-farm trials are encouraging as well, showing that a practical method of producing dehulled barley may be close. Grain dehulled on the farm is consistently below 0.5 ppm of DON, which makes it suitable for all categories of livestock. The cost appears to be at or below twenty cents per bushel. The resulting dehulled barley is now able to replace wheat or corn in rations and so has a higher monetary value offsetting the cost of dehulling.
Manitoba Agriculture and Food staff are now looking at the possibility of dehulling or pearling wheat to effect a similar reduction of DON contamination. Hulls can be used for composting mortalities or for bedding in some situations.
Further work is being done in several locations in Manitoba in hopes of developing a method of dealing with this difficult mould.