Q: I have a barrel of ground corn that had been put through a dryer. My question is, with all the trouble farmers have been having with moldy corn, does the drying process eliminate the mold enough to use safely for mixing with horse feed?
A: It is important to remember that the presence of visible molds is only an indicator of a possible problem and that a sample needs to be analyzed to identified the mold type and amount to determine its potential negative impact. Drying corn to 14% moisture or less will inhibit mold growth, but does not necessarily kill the existing molds. Given favorable growing conditions of moisture above 15% and appropriate temperatures, molds can continue to grow. Also, drying does not eliminate mycotoxins from the corn. Mycotoxins in the corn before drying, will still be there after drying. Mycotoxins are diverse compounds produced by fungi (molds). However, not all mold produce mycotoxins. Gibberella, Aspergillus, Fusarium, and Penicillium are known to produce the following mycotoxins; vomitoxin (Gibberella), aflatoxin (Aspergillus), and fumonisin (Fusarium). Aflatoxins and fumonisins are detrimental mycotoxins with respect to equine performance, health, metabolism, and reproduction.
Aflatoxins have been shown to have severe adverse effects on horses. Clinical signs include weight loss, anorexia, poor body condition, increased body temperature and heart rate, lethargy, depression, lameness, and bilateral congestion of the eyes. Aflatoxins are more commonly found under hot and dry environmental conditions.
Horses are susceptible to the feeding of grains contaminated with fusarium mycotoxins. Dietary concentrations as low as 10 mg/kg of fumonisins are associated with fatal equine leukoencephalomalacia (ELEM). ELEM is a multifocal neurological disease of horses characterized by signs of depression, abnormal behavior, head pressing, ataxia, agitation, dementia, and blindness.
Testing moldy corn is critical. Even if mycotoxins are not present, feeding and palatability may still be affected. Most forage testing labs in Minnesota will also test for molds and mycotoxins.
By K. Martinson, PhD and J. Linn, PhD, University of Minnesota