Study: Hail-damaged corn may not be adequate cattle feed
AMES – New research on hail-damaged corn led by Iowa State University shows that hail damage during grain fill increases the risk of ear rot diseases and mycotoxin contamination.
The findings are important because hail-damaged corn is often used to feed livestock, which can become ill or refuse feed if mycotoxin concentrations are too high.
“Hail damages crops somewhere in Iowa every year. But until recently, there was little data to quantify effects of hail damage on grain quality,” said ISU plant pathologist Alison Robertson.
Robertson studied the issue with ISU colleagues Charles Hurburgh, director of the Iowa Grain Quality Initiative; Gary Munkvold, Seed Science Endowed Chair and plant pathologist; and Steve Ensley, clinician with the Veterinary Diagnostic Laboratory.
Robertson analyzed injured corn ears collected from several Iowa fields damaged in two major hail storms in July and August 2009.
The storms affected 1.3 million acres in northeast and west central Iowa. Because they occurred in later stages of the crop’s growth, these storms offered a rare chance to study effects of hail on grain quality.
One way grain quality declines is through growth of molds on hail-bruised kernels. Some molds produce toxins leading to ear rots; others discolor kernels, reducing marketability.
The researchers wanted to answer a common grower question: What impact does hail damage to developing kernels have on corn grain quality, ear rot severity and mycotoxin contamination?
They found that as hail damage to kernels increased, so did severity of ear rots and with the ear rots, the presence of certain mycotoxins.
Fusarium, Gibberella and Cladosporium were the main molds found in the study. Fusarium ear rot can contaminate grain with toxins called fumonisins. The toxins deoxynivalenol and zearalenone are produced by the fungus that causes Gibberella ear rot.
Cladosporium does not produce toxin, but does create black mottling on kernels, Hurburgh said. “This classifies as ‘total damage’ in the official U.S. grades and therefore creates marketing issues.”
Researchers also found that where deoxynivalenol, more commonly known as vomitoxin, was found, zearalenone was usually present as well.
“Swine are very sensitive to vomitoxin,” Robertson said. “And zearalenone is an estrogen-type mycotoxin that can affect breeding pigs.”
Because zearalenone poisoning affects reproduction, effects are hard to see. But vomitoxin, to which swine are most sensitive, causes more visible signs of sickness such as poor weight gain, Ensley said.
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