Pick up any feeding guide on distillers’ grains and somewhere in the text you will find a warning about the potential for mycotoxin contamination.

“This is not to say that distillers’ grains are more likely than other feeds to be contaminated, but rather that mycotoxins from the original corn can be concentrated in the spent grains,” says Lon Whitlow, North Carolina State University specialist.

If the original corn is contaminated with mycotoxins, the distillers’ grains produced from it can contain two to three times the amount of the corn’s original concentration. That’s because only about a third of the original grain remains in the distillers’ byproduct. “Mycotoxins are not thought to be destroyed during the distillation process,” Whitlow notes. “None of the mycotoxins are found in the ethanol.” Research is still refining mycotoxin retention levels from the original corn to distillers’ grains.

Raising concern further is the fact that mycotoxins can be produced during storage if the grains are allowed to mold, which is most likely to occur if grains are insufficiently dried or wet grains are improperly stored. This year’s shortage of storage could raise those concerns. Also drought years raise the aflatoxin risk, and increasingly, this year is gaining that label. 

A variety of mycotoxins can contaminate corn grain, but aflatoxin is the greatest concern. The U.S. Food and Drug Administration sets an action level for aflatoxin in feed if it exceeds 20 ppb. For fumonisin, FDA’s guidance values for swine feed is that it should be below 20 ppm.

Other mycotoxins like deoxynivalenol (DON), zearalenone, T-2 toxin and ochratoxin also can contaminate corn and be concentrated in the distillers’ grains, Whitlow notes. FDA’s feed tolerance level for DON in swine feed ingredients is less than 5 ppm.

“Guidance values are related to individual mycotoxins, but it’s important to note that mycotoxins rarely occur individually,” Whitlow says. “If analysis determines the presence of one particular indicator mycotoxin, evidence suggests that others are likely present.”

Mycotoxins are often synergistic, meaning that combinations have a greater impact than single toxins. As a result, seemingly low levels of individual mycotoxins become important. “So even if the feed samples tested come back as being ‘low’ for a particular mycotoxin, there may still be an issue worthy of concern,” he adds.

While there’s been little official monitoring, commercial testing laboratories report substantial concentrations of DON in both corn and distillers’ grains from parts of the Midwest this past year. “Because these results are from commercial testing laboratories, the samples and results are not representative, but more likely represent problem situations where mycotoxins are suspected,” Whitlow notes. “Mycotoxins in these samples may have originated from the corn or were produced from mold growing during storage of the distillers’ grains.”

The laboratory reports do illustrate that distillers’ grains, like all other feeds, have the potential to contain mycotoxins and can be a feeding problem. This year USDA has been sampling distillers’ feeds nationwide, during all seasons to determine aflatoxin incidence and concentrations. The results are due this fall. “Hopefully, these data will give us a better idea of the aflatoxin prospects in distillers’ grains coming directly from the distillery,” Whitlow says.

There are ways to decontaminate feeds. “Research shows that several chemicals and processes can destroy some of the mycotoxins during the fermentation process or in the distillers’ feeds after production,” Whitlow adds. “Research also has identified feed additives, such as B-glucans, which can reduce mycotoxins’ toxicity by reducing mycotoxin absorption in the animal.”

The National Corn Growers Association has made mitigating mycotoxin contamination one of its seven priority areas.

More testing is needed. In an IowaStateUniversity study, two out of 20 ethanol plants were testing all inbound corn while 13 were routinely testing corn but not every load. “The indication was that distillery managers would increase the test frequency if a problem was suspected in the current harvest year,” Whitlow says. But it’s still your responsibility to ensure that your feed ingredient supply is tested.

So it’s always wise to be aware. “In some years it appears necessary to increase mycotoxin monitoring by increased observations and testing,” Whitlow adds. “Proper storage and feeding management of distillers’ grains is essential to prevent mold growth and mycotoxin production.” Better to be safe than sorry.