With recent rains causing delays in completing the wheat harvest, there have been reports of damaged wheat, particularly in the northern areas of South Dakota. In some cases, factors such as vomitoxin or ergot have caused the affected wheat to be unmarketable through traditional channels.
Vomitoxin is a mycotoxin that may be produced in wheat grain infected by Fusarium head blight or scab. The risk level of the grain cannot be determined by visual examination, as not all wheat with scab contains vomitoxin and those levels do not necessarily correlate with the physical symptoms in the grain. The only certain measure is a lab analysis.
Feeding damaged wheat to livestock is one way to salvage value from the crop. Wheat can work well in cattle diets with some limitations. Wheat is highly fermentable in the rumen and if fed at high levels can result in bloat, acidosis, and digestive upsets if not managed carefully. For those reasons, wheat should not exceed 40% of the diet on a dry matter basis.
Vomitoxin presents another set of concerns. The FDA guidelines on vomitoxin levels in feedstuffs fed to beef cattle older than 4 months are 10 ppm, as long as the feedstuff does not exceed 50% of the diet.
Be extremely cautious feeding wheat screenings. The cleaning process removes a large percentage of the smaller, scab-infested kernels resulting in increased concentration of mycotoxins in the screenings. The safest option is to not feed wheat screenings from scab-infested wheat at any level. At a minimum, screenings need to be lab tested prior to feeding.
These mycotoxins can also be found in the straw. The safest option for straw from fields known to contain vomitoxin would be as bedding for feedlot or mature cattle. If the straw is to be fed, it should be tested prior to feeding and diluted according to the 10 ppm and 50% of the diet limitations.
Ergot is another defect sometimes found in wheat under certain growing conditions. Wheat containing more than 0.05% ergot may be rejected in the commercial grain trade. Ergot concentrations greater than 0.1% have affected cattle performance. More information on ergot and potential problems with livestock can be found in the article: Ergot: A potential poisoning problem for livestock.
Delayed harvest can also lead to issues with sprouted wheat. This grain will be significantly discounted in commercial channels. However, there have been no significant performance losses observed in cattle feeding trials, indicating that marketing sprouted grain through cattle is a viable option. These grains should still be tested for vomitoxin and fed at no more than 40% of the diet dry matter like any other wheat.
Other tips for feeding wheat (normal or damaged) include:
- Adapt cattle to wheat by starting at low levels (10 to 15% of the diet) and increase that amount in steps over a number of days.
- Wheat should be coarsely cracked for improved digestibility, but not finely ground.
- Including an ionophore will help reduce over consumption and acidosis.
- Do not feed wheat in a self-feeder.