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Moldy Hay Leads to Fungal Abortions in Pregnant Cattle

If this was a year that you struggled to get your hay dry or ended up storing it semi-wet, you should be on the lookout for fungal abortions in your herd. Some herds have seen up to 10% of pregnant cattle aborting due to mold, but a more typical number is one or two fungal abortions per herd. 

Almost every farm encounters mold in one form or another, but forms like Aspergillus and Mucor in particular can be dangerous for pregnant cattle. These forms are most often found in cattle feed, hay, silage, and wet byproducts, and can lead to fungal abortions when ingested by expecting cattle.

“Many animal feeds naturally have around 10,000 mold organisms per gram of forage,” says Gregg Hanzlicek, director of production animal feed investigations at the Kansas State Veterinary Diagnostic Laboratory. “Once we start to be able to see the mold, there are many times around a million or more organisms per gram.”

Fungal abortions, also known as mycotic abortions, typically occur when a cow is around six to eight months pregnant. Hanzlicek has seen slightly more fungal abortions in 2016 than he has seen in past calving seasons.

Moldy Hay
“We think the primary way cattle become infected is by breathing into the respiratory system the mold spores that are in the feed,” Hanzlicek says. Testing hay is important to understand mold levels.

If producers are feeding moldy hay, they can try to dilute the mold in the hay by mixing it with non-moldy hay in a mixer wagon. If that’s not an option, feed the moldy hay out in an open area where the mold may blow away.

To limit mold growth, packing corn silage is known to be effective. Mold inhibitors in feed are really only helpful in programs that use a total mix ration or go through a mixer wagon and into a feed bunk.  

Medical Signs
Unfortunately, there’s no way to predict whether or not a cow will suffer from a mycotic abortion. 

“The heifer or cow that has the mold doesn’t act sick; she just aborts the fetus,” Hanzlicek says. “A small percentage of the aborted fetuses will have either red or white circular lesions on the skin. The white lesions look similar to ringworm.”

Because that’s so uncommon, the easiest way to find out if the abortion was fungal is to send in samples to a lab. Submitting the placenta is the ideal tissue sample for veterinary diagnostic labs to have along with other tissue samples.

“The only way to determine it is to microscopically look at the placenta,” says Hanzlicek. “If we find mold hyphae growing in the placenta, then we know for sure mold was associated with that abortion.”

Even if there was a way of diagnosing these abortions prior to them happening, there are no medical treatment options for prevention. 

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