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Mold and corn quality issues

Tue, Nov 17th, 2009
Posted in Agriculture

While searching for information for a number of farmers with questions about the mold in their corn, I soon learned this was a very widespread problem covering most of the upper Midwest. Not every field is affected and not every variety of corn is equally impacted. These are some of the important pieces of the information that address this issue.

"If the corn is not harvested and dried properly, various fungi may continue to grow," said Extension plant pathologist Dean Malvick. "Both types of mold-superficial growth on the surface of the kernels and significant ear and kernel rots-may cause greater problems."

At heightened risk for mold and mycotoxin health and disease problems are young animals, breeding animals and lactating dairy cows, with swine and poultry species more susceptible to these problems than ruminants. Mycotoxins in large doses can cause acute health, reproduction and production problems. However, the most likely scenario with feeding of moldy and/or mycotoxin containing feeds is a higher incidence of general, chronic health problems, poor reproduction and overall poor animal growth or milk production.

"In general, livestock producers should avoid feeding grain or grain silages containing colored molds (pink, blue green)," said Extension livestock specialist Jim Linn. Mycotoxins, on the other hand, are not visible and their presence depends on the type of fungus present and the storage environment. Livestock producers should test grains and silages for mycotoxins before feeding.

To diagnose and help identify mold and kernel infection, producers can send samples to the University of Minnesota Plant Disease Clinic. For more information on the clinic and how to submit a sample, visit Other labs are also running tests.

"Diagnosis and identification can help clarify the problem and reduce it," Malvick said, "but harvest and drying may be part of the solution."

If producers are experiencing pre-harvest mold problems, 2009 is not a good year to use slow- or low-temperature drying methods, warns Extension agricultural engineer Bill Wilcke.

"Under these types of conditions, higher temperature drying methods that reduce the moisture content of the grain within a few hours or a few days are preferred," Wilcke said.

Higher temperature dryers aren't likely to run hot enough to kill the molds, he explains, but they do slow mold growth by reducing the grain's moisture content. The agitation of the grain during high-temperature drying is also likely to rub off some kinds of molds.

Noah B. Litherland, Department of Animal Science, University of Minnesota, has come up with ten take home messages to think about if you are concerned about mold in dairy feed. I feel many of these suggestions would apply to other classes of livestock as well: (1) Testing for mycotoxins can provide an estimation of risk. Tests can be expensive and sampling and feed variation can reduce the usefulness of the results. (2) Adding a mycotoxin binder can reduce the impact of toxins by reducing their impact in the digestive tract and/or not absorbed (binders include yeast cell wall extracts or MOS products and clay binders). (3) Drying wet corn below 15 percent moisture stops further toxin development. (4) High moisture corn could increase the risk of additional mold grow until the pH of the fermented corn drops. (5) Adding a grain inoculant to speed up fermentation and stabilize the wet corn is recommended. (6) Young animals and pregnant cattle are at higher risk while steers can tolerate higher levels. (7) Removing fines, damaged seeds, and cracked corn kernels can reduce toxin risk. (8) Distillers grain produced from ethanol production can concentrate the level of toxins in the original corn used; know your sources of distillers grain. (9) Corn silage made late in the season with mold damage could have toxins, but the low pH will stop additional toxin production. And (10) Adding propionic acid at the time of ensiling can reduce mold development in wet corn.

To address the difficulties this harvest season, Extension is maintaining a late harvest resources page on the Extension website. Current information on the page includes: harvesting, handling and storing wet corn and soybeans; grain drying; soil fertility and tillage; and corn mold. As the season moves along, focus has begun to shift to concerns about using moldy grain for livestock feed. We are working with species experts to get information on this issue up within the month.

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