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.
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.
The FDA guidelines on vomitoxin for grains fed to beef cattle older than 4 months is 10 ppm, as long as those grains do not exceed 50% of the diet. Wheat should be limited to 40% of the dry matter in cattle diets.
Be extremely cautious feeding wheat screenings. The cleaning process removes a large percentage of the smaller, scab-infested kernels resulting in increased concentration of any mycotoxins present. The safest option is to not feed wheat screenings from scab-infested wheat at any level, at a minimum these feedstuffs have 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 accordingly.
Ergot in wheat has also been reported in northern South Dakota in 2015. 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 iGrow 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.
Other tips for feeding wheat (normal or damaged) include:
- Wheat is highly fermentable in the rumen, leading to increased potential for digestive upsets. Adapt cattle by introducing wheat 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.