– Stan Smith, OSU Extension, Fairfield County PA
It’s now apparent that much of Ohio’s wheat crop is testing positive for vomitoxin. Results of “quick tests” completed at grain elevators I’ve contacted have ranged from only 1 ppm to over 10 ppm.
In some cases the elevator is accepting the wheat after discounting the price anywhere from a nickel per bushel up to more than a dollar per bushel. In fact, in some cases the wheat has even been rejected for acceptance at any price by the elevator. While the negative economic impact on the wheat grower quickly becomes obvious, by contrast, this may be an opportunity for cattle feeders.
When wheat receives up to a $1 per bushel discount, its value becomes equal to or less than the current value of corn per pound. Add to that the fact that protein content is greater in wheat than corn and you discover that wheat, which may have once been intended for human consumption, potentially becomes a cost effective component of a beef cattle ration.
Below, OSU Extension beef and sheep veterinarian Dr. Bill Shulaw responds to some of the questions we’ve been receiving in regard to the use of wheat and straw for beef cattle. In the subsequent article, OSU Extension beef specialist Dr. Steve Boyles goes over the basics of including wheat, and especially wheat with known amounts of vomitoxin, into beef cattle rations.
Q: Do all vomitoxin tests yield equally reliable information? In other words, can I take the results of the “quick test” for vomitoxin which was done at the grain elevator and use that information to formulate a safe wheat inclusion rate for my beef cattle?
A: Elevators have to use rapid and relatively inexpensive “screening” tests when faced with the large numbers of loads submitted to them during wheat harvest. Some of these tests are semi-quantitative which means that they give an approximate level of vomitoxin in the grain. They are not meant to be definitive for the quantity of vomitoxin in the grain, and other more accurate tests are used for that purpose if needed. The USDA provides guidelines for this testing, and specific information can be found at: http://www.gipsa.usda.gov/fgis/handbook/don_inspec.aspx. Some variability among results should be expected from these screening tests and can be largely attributed to the sample itself, sample preparation, the analytical method, and of course, the technical expertise of the laboratory in preparing the sample and using and handling the test kits.
If farmers decide to feed wheat to cattle or other livestock that they suspect may be contaminated with vomitoxin, they should consider sending representative samples from that source to a laboratory such as the Ohio Department of Agriculture’s Division of Plant Industry – Grain, Feed, & Seed Section (614/728-6383) for testing to verify the level of vomitoxin present.
Q: Is vomitoxin the only mycotoxin I have to worry about if I want to feed this wheat?
A: Vomitoxin (DON or deoxynivalenol) is probably the most common mycotoxin found in small grains like wheat and barley, and it is produced by some fungus species of the genus Fusarium. However, these species may also produce other mycotoxins and you may remember the concerns about DON and zearalenone in last fall’s corn crop. The presence of a mycotoxin, like vomitoxin, in a grain sample indicates that suitable conditions for fungus growth and mycotoxin formation have occurred. Although swine are the most susceptible to the effects of vomitoxin (vomiting and feed refusal) and cattle more resistant, some of the other mycotoxins produced by Fusarium species, such as T-2 toxin or fumonisin, can cause clinical and subclinical disease. Many laboratories such as the ODA laboratory mentioned above offer testing panels that check for the other important mycotoxins besides vomitoxin, and if farmers plan to feed wheat or other grain they suspect has mycotoxin contamination, testing a representative sample would be wise.
Q: Is there risk of vomitoxin levels changing while the wheat is in storage causing the need to retest it occasionally throughout the feeding period?
A: Fusarium growth and vomitoxin formation occur in the field. Cleaning and removing the dockage may remove a substantial portion of the vomitoxin. Storing the cleaned wheat at low moisture content should prevent further fungal growth and mycotoxin formation (some references suggest a minimum of 19-25% moisture is needed for Fusarium growth). If there is any question about storage conditions, then retesting to be certain of what you are feeding may be advisable.
Q: Is there risk to cattle or calves when using the straw from vomitoxin-contaminated wheat fields for bedding?
A: This is a difficult question as there appears to be little or no information from research to answer it directly. Vomitoxin, and potentially some other mycotoxins, can be found in the straw and other parts of the plant. In some cases the concentration of vomitoxin may approach that of the grain. If animals are intentionally fed contaminated straw as a regular part of their diet, such as might occur if wheat is used for balage or silage, then a potential disease risk might be present. However, the new FDA Guidance for Industry advisory levels document (published online June 29, 2010) indicates that wheat containing up to 10 ppm of vomitoxin can be fed to adult beef cattle with the stipulation that the total ration should not exceed 10 ppm for beef cattle and should not exceed 5 ppm for adult dairy cattle. For calves and other animals except swine, wheat containing vomitoxin at up to 5 ppm can be fed if it composes no more than 40% of the diet. Wheat containing 5 ppm vomitoxin can be fed to swine if it composes no more than 20% of the diet. You may review the new FDA Guidance for Industry document in its entirety here: http://www.fda.gov/downloads/Food/GuidanceRegulation/UCM217558.pdf
It seems unlikely that cattle, or other livestock, would voluntarily consume a sufficient amount of dry straw bedding containing these levels of vomitoxin if other nutritious feed were available.
Data on risks from airborne particles containing vomitoxin (and other mycotoxins) or risks from skin exposure for animals are equally scarce. Some research addressing these risks for humans is available but is not directly applicable for animals in their environment. It is clear that the greatest hazard for vomitoxin is when it is in the diet. In light of the current state of our knowledge on acceptable dietary levels of vomitoxin in human and animal diets, it is difficult to see how wheat straw bedding from this year’s crop might pose a risk to livestock.
For more information on the health and safety aspects of handling wheat which tests positive for vomitoxin, as well as legal and other aspects of managing wheat this year and perhaps in the future, please review 4 timely and related articles in the June 29 issue of the OSU Agronomic Crop Team CORN newsletter.