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When brainstorming examples of dietary energy sources for livestock, corn is a top contender. Kernels contain high levels of digestible starch, and almost the entire plant can be utilized by animals in some form or another. Corn fed straight from the field, especially if growing conditions have been imperfect, is not always a safe choice for horses, however.

One of the most common dangers to horses is the mycotoxin fumonisin, which is produced by a fungus that proliferates on growing corn plants. Mycotoxins cause neurological damage and other health problems.

Specifically, fumonisin causes equine leukoencephalomalacia (ELEM), also known as moldy corn poisoning. The earliest visible sign of ELEM is reduced food intake, which is soon followed by disorientation, blindness, facial paralysis, ataxia, and death. Typically, once clinical signs are noticeable, the damage is too advanced to save the animal. Upon death, necropsies show softened cerebral hemisphere tissue, muscular deterioration, and signs of cardiac failure.

Fungal growth is expedited by adverse weather conditions, especially long wet seasons. There is no guaranteed way to identify fumonisin-infected corn with the naked eye. Some kernels may exhibit red discoloration on the kernel cap, and others may have white streaks radiating from the tops of the kernels. Some afflicted plants look completely healthy.

The only trustworthy way to evaluate corn is through on-site or laboratory testing for mycotoxin levels. This testing is routine for reputable feed manufacturers, so there is little chance infected corn finds its way into high-quality feeds. The danger occurs when infected corn does not go through stringent testing prior to feeding.

Corn has been fed to horses for centuries, and it will continue to be, but it should always be sourced, tested, processed, and managed diligently for safety’s sake.

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