Dealing with DON in wheat
Wheat harvest will begin soon in southern Indiana and some fields have high levels of Fusarium head blight (scab). It is important to be aware of the impacts of the mycotoxin deoxynivalenol, also known as DON or vomitoxin. DON is produced by the fungus that causes Fusarium head blight, and it is especially toxic to swine, but consumption of high levels of the toxin can impact the health of many animals. Reports vary on the disease and DON levels in wheat, but buyers may dock grain when contamination levels reach 2 ppm DON.
If wheat fields have not been harvested yet, check fields to determine if scabby grain is present. If the disease is present, increasing the fan speed on the combine at harvest can blow out the lighter scab-infected kernels, which contain most of the DON. There are many questions about how to handle and market scabby grain with high levels of DON, and we have attempted to answer the most frequently asked questions in this article.
1. What is DON or vomitoxin?
DON is a toxin produced by the fungus that causes scab. The toxin is referred to as deoxynivalenol and vomitoxin. The occurrence of scab does NOT automatically mean that DON is present, but high levels of scabby kernels in the harvested grain should be suspect. Conversely, high levels of DON can occur even when disease levels are low. DON can affect the health of animals that consume contaminated grain. DON also can affect flavors in foods and baking quality.
2. How does DON affect livestock?
DON causes feed refusal and poor weight gain in livestock. Hogs are most sensitive to DON, even at one part per million (1 ppm) contamination of hog feed. Cattle, sheep and poultry are more tolerant of DON. Diluting scabby wheat with normal quality grain may be a logical method of feeding wheat safely to on farm livestock.
3. What are safe levels of DON?
The Food and Drug Administration has established DON advisory levels as follows:
- 1 part per million for finished grain products for human consumption.
- Swine: 5 ppm (not to exceed 20 percent of ration with finished feed = 1 ppm).
- Ruminating beef and feedlot cattle, over 4 months old: 10 ppm (not to exceed 50 percent of diet with finished feed = 5 ppm).
- Poultry: 10 ppm (not to exceed 50 percent of diet, with finished feed = 5 ppm).
- All other animals: 5 ppm (not to exceed 40 percent of diet).
4. How can I determine if grain has DON?
The presence and amount of DON from infected grain can only be verified through chemical analysis. There are a variety of commercial laboratories and quick test kits for mycotoxin analysis. Testing facilities in Indiana that analyze grain for DON are listed in the Extension bulletin: Diseases of wheat: Fusarium head blight <http://www.extension.purdue.edu/extmedia/BP/BP-33-W.pdf>.