Get Questionable Cornstalk Bales Tested Before Feeding

If you see mold on cornstalks in bales, get them tested for toxins before feeding.

Iowa State University Extension specialists are urging farmers who notice mold on bales of cornstalks to get the bales tested for toxins before using them for feed for cattle. For horses, even if you are just using the bales for bedding, get the moldy stalks tested. That's because horses are more susceptible than cattle to mold toxins, and horses may nibble on stalks that are used for bedding. Heavy rains in October affected the quality of cornstalks, which many cattle producers use to lessen their winter feed costs. The extra moisture, however, has increased the chance for mold and mycotoxins, or toxins produced by fungi, to develop.

Beth Doran, ISU Extension beef field specialist, recommends cattle producers have a mycotoxin test conducted on cornstalks that show any noticeable signs of mold before using them as feed. "But if the stalks don't see any visible mold, then chances are it is not going to be a problem," she says of mycotoxins.

Cattle are more tolerant than horses

Cattle are more tolerant than other animals, such as horses, to the most common mycotoxins associated with wet cornstalks – fumonisins and vomitoxins, says Doran, who works with the Iowa Beef Center at ISU.

However, she doesn't recommend providing any questionable feeds to animals that are more sensitive - such as breeding animals, young stock or livestock that are more fragile due to health or age.

What would happen if cattle do happen to eat some moldy stalks? Consuming these mycotoxins should not result in major health issues for cattle, says Gary Osweiler, a veterinary toxicologist at the Veterinary Diagnostic Lab at Iowa State. Refusal of the animal to eat the feed is the only well-documented effect on cattle that consume vomitoxins, says Osweiler, and cattle are less likely to show effects from consuming fumonisins. Fumonisins are more toxic than vomitoxins, but cattle are fairly resistant to them in comparison to hogs and horses.

"Even in bad years for fumonisins, we have never had an outbreak of fumonisin poisoning in cattle," he says.

Toxins are more dangerous for horses

Cattle can tolerate up to 100 parts per million of fumonisins without problems, while long-term consumption of just 5 to 10 ppm is considered dangerous to horses. Fumonisins in horses can cause a fatal disease called equine leukoencephalomalacia or ELEM, which destroys the animal's brain cells. And, even at low levels, fumonisins can cause liver disease, notes Osweiler.

Therefore, Doran says horse owners should definitely have a mycotoxin test performed before using any questionable cornstalks for feed or bedding. "With horses, I just wouldn't take the chance," she says. "Testing is a must."

To test for mycotoxins, Doran says the Veterinary Diagnostic Laboratory at Iowa State offers a qualitative test for $30 and a quantitative test for $35. "I know that's $65 in total, but that's pretty minor compared to reduced performance or the worst-cased scenario--a dead animal," says Doran.

Using affected cornstalks for bedding for cattle should be okay. "Producers should simply move the cornstalk bales into the pens after the cattle have been fed, so they will be less likely to consume the stalks," she says.

The Iowa Beef Center at ISU was formed in 1996 by a legislative mandate. Its goal is to support the growth and vitality of the beef cattle industry in Iowa. As part of ISU Extension, the Beef Center also serves as a central access point for all ISU programs and research related to the beef industry.

For more information about the center, visit

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