Conditions Ripe for Mycotoxins

The past growing season in many parts of the country has created the perfect storm for elevated mycotoxin levels in winter feed supplies. ( Maureen Hanson )

It’s been a long, wet, protracted harvest season for much of the United States. In addition to the frustrations of getting crops in late and the onset of an early winter, many farms now are dealing with the potential for elevated mycotoxin levels in their feed supplies.

According to an Iowa State University Crop News Bulletin, the Iowa corn crop faced double exposure to mycotoxins this past year, thanks to drought early in the growing season and extreme rainfall just prior to harvest. Wet conditions meant corn stood in the field longer than usual, adding to the risk of mold development and subsequent mycotoxin production in the crop.

The presence of mold doesn’t necessarily guarantee the production of mycotoxins, but stress on the corn crop – in terms of drought, excess moisture, or plant disease – causes molds to produce mycotoxins as a sort of defense mechanism. Fungi similarly can produce mycotoxins.

According to Don Giesting, nutritionist with Provimi North America, mycotoxins will remain in feed even after the molds responsible for them have died or been removed, and also can be present when no visible mold exists. “They also are not destroyed by feed processing, even at high temperatures, and can be further concentrated in processed feeds and co-products, such as dried distillers grain from ethanol production,” adds Giesting.

Many molds can produce multiple mycotoxins, and dairy animals particularly risk exposure, because mycotoxins can be carried in so many of their feedstuffs, like grain, forages and co-products. “Mycotoxin effects usually are cumulative, and low levels of multiple mycotoxins can decrease immune function in animals that consume them,” Giesting explains.

He notes calves, young heifers and transition cows are most susceptible to the detrimental effects of mycotoxins. In addition to suppressed immunity, calves and heifers may have decreased feed intake, slower growth and reduced weight gain.

Mycotoxins can continue to proliferate even when feed is in storage. Silage is particularly at risk of deterioration and mycotoxin proliferation if it is exposed to oxygen, which is more likely to occur if it is harvested late and thus packed at a drier moisture level.

Giesting recommends sampling and testing feedstuffs for mycotoxin levels, particularly in high-risk years when growing and harvest conditions were less than ideal. “Be sure to take samples from five or more locations for representative testing,” he advises. “Combine and mix multiple smaller samples to make on larger sample, then sub-sample this to submit for analysis.”

If high mycotoxin levels are found, it may not always be feasible to discard all affected feed. The situation can be managed by blending out the feed source; using it to feed livestock groups that are less susceptible to the effects of mycotoxin; and/or enhancing rations with a yeast cell-wall extract product, clay binder, or yeast product.

Learn more about mycotoxins at the Crop Protection Network’s Mycotoxin FAQ.