Editor’s note: The following was written by Charles Hurburgh, Iowa State University professor of agricultural and biosystems engineering, Alison Robertson, professor of plant pathology and microbiology, Erin Bowers and Jason Ross for the university’s Integrated Crop Management News website Feb. 26.
The 2 bu./acre Iowa corn yield reduction (from the previous 2018 report) in the Feb. 9 crop report demonstrated the impact of late-season wet weather. Corn quality and potential food safety issues are also determined late in the growing season.
According to data recently completed by the Iowa Department of Agriculture and Land Stewardship, levels of the mycotoxins deoxynivalenol (also known as vomitoxin) and zearalenone are elevated in this year’s Iowa corn crop.
Vomitoxin primarily affects digestion in swine, while zearalenone has negative effects on reproduction in most monogastric animals. Dogs, cats, and gilts are most sensitive to zearalenone.
In the 102 samples collected by IDALS warehouse inspectors, vomitoxin was detectable in all, and zearalenone was detectable in 82 samples. All regions of the state were affected. Those two toxins are produced by the same fungus and often occur together.
Neither vomitoxin nor zearalenone are regulated by FDA. Because both are capable of causing negative animal health and production effects, there are guidelines for feeding. The two other mycotoxins surveyed, fumonisin and aflatoxin, were not present in significant amounts in these 2018 corn samples.
Due to widespread occurrence of the two toxins, corn users should test the toxin levels of 2018 corn and direct corn in excess of recommended feeding limits to less sensitive livestock species.
A directory of some regional mycotoxin testing laboratories is located on the Iowa Grain Quality Initiative website at https://bit.ly/2SB6THe. Producers have access to the Iowa State University Veterinary Diagnostic Lab; a veterinarian can submit samples there.
Ethanol processing concentrates toxins by a factor of three (relative to the originating corn) in dried distiller’s grains (DDGS). Therefore, swine feeders mixing corn and DDGS from the same area have an increased risk of exceeding guidelines even if the corn itself does not.
Proper sampling is crucial to accurate toxin testing. Take multiple sub-samples throughout the grain lot, or from multiple delivered loads contributing to the lot being evaluated, to achieve a total sample weight of approximately 10 pounds. Submit the entire 10 lbs. to the laboratory. The laboratory will grind the entire sample, then subsample for the analysis.
Toxin levels are not likely to increase in well-managed storage but expect that this issue will be present through 2019 crop usage. Drying and aeration will not reduce toxin levels. Cleaning of fines may reduce toxin levels, by removing susceptible materials (broken or lightweight kernels and fines). The cleaned grain should be retested to verify that toxin levels were reduced.