Dealing with Moldy Corn

Concerns about mold in corn? Not all mold feeds have mycotoxins and can still be used with precaution.
Dealing with Moldy Corn - News


Photo by Alyssa Collins

This rainy summer has raised some concerns about mold in corn. This could potentially have some negatives effects on production and the health of the animals. More drastic effects can be seen if there are potent mycotoxins that can cause some serious health issues. Respiratory diseases and abortions are some of the most common disorders when dealing with mycotoxins. However, not all moldy feeds have mycotoxins and they can still be used with some precaution.

Some practices could be implemented to avoid major negative effects on the herd. The first step is to send a few samples to the lab. Knowing the exact mold spore load will help to design an appropriate feeding strategy. According to Adams et al. (1993), mold spore counts below 2M are relatively safe. However, when the load of spores is greater than 5M, it is better to discard the feed to avoid health issues. For instance, if the mold spore count on an air-dried feed sample comes back with a count between 500K and 1M spores per gram, no further actions will be needed. It is safe to use. But if the count is above 2M, some precautions need to be taken. This may include, dilution of the infested feed with other feeds, discount in energy value (x 0.95) and more importantly, keep a close eye on the performance of the animals. They will be the final judges.

But if the animals start to present suspicious signs and symptoms of diseases that are not easy to explain, and production is greatly affected, then it would be wise to test for mycotoxins. The sampling can start with the final feeding product. In case of ruminants, the TMR should be the first item to be sampled and in monogastric, the grain mixture. If the results come back positive, then each ingredient should be tested to identify the source of mycotoxin. This includes forages and grains. Wet samples with a moisture content of 15% or more must be handle accordingly to recommended practices to avoid mycotoxin growth after collections. It is crucial to collect a representative sample since mycotoxin might develop in spotted areas of silos, bunk or bins.

Also, it is important to remember that feed intake might decrease as palatability will be reduced. Milk production may decrease 5 to 10% when feeding moldy feed. This decrease in milk yield might greater when feed contains mycotoxins. Keeping track of the milk production and feed refusals will help to determine what actions need to be taken to achieve production goals.

In order to alleviate some of the effects that mold, and mycotoxin may cause, some practices are recommended. Discard all the sources of contaminations. Removed all the moldy grains that are suspected to have mycotoxins. Use mold inhibitors (sodium or calcium propionate, or organic acids) for dry feeds with 15% or more moisture content (Adams, et al., 1993). Add aluminosilicate or bentonite in ruminant rations at 0.5%. These compounds may bind with mycotoxin and decrease its absorption in the GI tract (Adams et al., 1993). Studies conducted in dairy cows found a reduction of 33000 cell/ml in SCC of milk of animals feed rations contaminated with mycotoxins (Stary, et al., 2017). Additionally, they found a decrease on occurrence of metabolic diseases.

When feeding moldy feeds different health problems can occur in addition to a decrease in production. However, there are many practices that can help to design a strategy to prevent negative effects. Even though we had a wet summer season, keep in mind that a correct management of feed before and after harvest can make a big difference.


Adams R., Kephart K., Ishler V., Hutchinson L., and Roth G. 1993. Mold and mycotoxin problems in livestock feeding. Accessed Sep 25, 2018.

Stary j., Coudkova V., Vrbova A., Svoboda V., and Marsalek M. 2017. Aluminum silicate clay as mycotoxin absorbent in dairy cattle feed. J. Vet Sci Med Diagn Vol 6:1