Testing Is Critical for Mycotoxin
Published: Friday, October 9, 2026
High mycotoxin levels pose a potential risk when feeding grain and silage to livestock, but visual symptoms alone cannot confirm toxin presence. Testing is critical to identify the presence and type of toxin.
Suspect grain should be tested for vomitoxin, zearalenone and other trichothecene mycotoxins, since this is the only way to truly assess risk. Vomitoxin (deoxynivalenol or DON), along with other common mycotoxins, can cause feed refusal, poor weight gain, and, in rare cases, vomiting and hemorrhaging.
These toxins can be produced from common field fungi such as Gibberella. However, the presence of visible fungus is not proof of mycotoxins, or vice versa. Confirming toxin presence is also challenging from a sampling perspective, because toxins often exist in a non-detectable form. Proper sampling techniques are important to accurately test for mycotoxins.
"Mycotoxins can be very sporadic in a field or in a bunker, and a single sample might not be very representative of that field or that bunker," said Adam Krull, Pioneer senior nutritionist. "The largest source of variability is related to how the sample was collected."
One sampling method is to use a probe sample on recently blended lots of grain since mold growth usually occurs in spots. Another method is to collect small samples as the grain moves in or out of bins. With both sampling methods, the collected grain is pooled into a representative sample for that lot.
Although visible mold can signal a potential issue, appearance alone is not a reliable indicator of mycotoxin contamination. Proper sampling and testing remain the best way to assess risk.
According to estimates, 70% to 90% of all mycotoxins are on the plant prior to harvesting or ensiling. Growers can minimize field-produced toxins by:
• Planting hybrids with insect, stalk rot and ear mold resistance to reduce fungi populations and access sites.
• Isolating silage from crops exposed to severe drought or hail damage.
• Considering traditional tillage methods to reduce fungal spore loads in crop residues.
While many mycotoxins develop before harvest, management decisions during harvest and storage can also affect risk. Earlier harvest results in lower DON concentrations, because it allows less time for continued mold growth and toxin production as the grain slowly dries below 20% moisture.
After harvest, artificial drying can arrest mold development and mycotoxin production. Grain with significant ear rot symptoms from the field should be dried at high temperatures as quickly as possible to 15% or less to minimize the risk of mycotoxin development.
Because of the unpredictability associated with stored grain, no matter how carefully it is dried and aerated, frequent observations are necessary to head off developing problems with mold and mycotoxins. Weekly observations are recommended during warm months, and every two weeks during the winter.
Observations should include inspection for overall temperature, crusts or mold on the grain, moisture in the bin, moldy odor and warm spots. If any problems are detected, steps should be taken immediately to reduce the temperature, aerate the bin, break up hot spots or remove spoiled grains.
Return to Top of Page