26 NEBRASKA CATTLEMAN August 2026 PRODUCTION MYCOTOXINS AND DROUGHT Be in the Know TRESSA LAWRENCE | CONTRIBUTING WRITER NEBRASKA The untimely rains of last fall and the drought conditions this year have experts reminding feeders that there is a higher risk of mycotoxins in their feeds. Crops grown under strained conditions, such as drought, or put up under less than ideal circumstances, such as untimely rain, can be more prone to mycotoxins, which are toxins produced by molds that can accumulate in crops, forages or feed products. Mold can develop in crops while they are growing in the field or later when the crops have been stored for feed. “If you are harvesting your own fields, it’s always a good idea to go and scout, because molds can be easier to identify in the field,” explains Mary Drewnoski, Ph.D., Nebraska Extension beef systems specialist. “The other type of mold that we have is not really associated with drought conditions, what we call storage mold. With silage, if you didn’t get it packed well and there is a lot more oxygen in there, you can get mold growth. These can produce an aflatoxin that can be problematic to cattle.” Mycotoxins issues in cattle are not necessarily immediately apparent. A good way of looking at it is that the mycotoxins can weaken the foundation of health and growth that you are trying to build in your cattle. As a result, various symptoms can easily compile due to the cattle’s weakened immune system, most obviously presenting as a failure to thrive or being slow to gain weight. High levels of mycotoxins in feed can also lead to reduced conception rates in breeding cattle. “The highest risk is always pregnant or breeding animals along with really young animals, with the lowest risk usually being finishing cattle,” Drewnoski says. “A common sign of mycotoxins is reduced feed intake and, therefore, reduced performance and growth. But some of them, like aflatoxin, can cause reduced liver function. If you’re feeding really high levels of it, then you also see reduced immunity. The problem with mycotoxins is that it’s not a very clear symptom, it’s a combination of things that you see where the animals just are not doing as well as normal, and you start to question what’s going on.” Detecting Mold and Mycotoxins As Drewnoski mentioned, the first step of monitoring is to hit the fields if you are growing your own feed crops. Once you identify mold in your field, you can determine what kind of mycotoxins you need to test for in your feed. Storage mold is often visible to the eye, and, therefore, easy to collect and test. If you are aware that you have storage CATTLEMAN mold, Drewnoski recommends minimizing the mold’s exposure to oxygen to prevent continued growth. By mixing moldy feed in with other feed products that do not have mold, you can dilute the effects of the mold and potential mycotoxins. “With the untimely rains last fall, we had a lot of producers who had a hard time putting up hay or had a lot of issues with corn,” says Rebecca Kern-Lunbery, feed testing product manager for Ward Laboratories in Kearny. “We saw corn being rejected at the elevators because of fumonisin. As a result, last fall we had those guys testing their corn grains in our lab.” In the last few years, Ward Laboratories has expanded the number of mycotoxins they can test on common grains and distillers co-products. They outsource forage-sample testing to other labs that can perform those mycotoxin tests. “This year, looking at the corn and distillers grain that was stored from last year, it would be a good idea to test them as they’re coming out of storage, because some of the mycotoxins do increase with storage and some remain the same,” Kern-Lunbery says. “We do know for sure last season we had grains coming off the field that were testing positive for mycotoxins, and, even if they aren’t increasing in storage, we know that they are not being destroyed in storage either.” Compounding Mycotoxins Mold does not necessarily indicate mycotoxins, but if your results come back with positive results for mycotoxins, even if they are below the threshold individually, it is important to talk to someone who understands the potential impacts of multiple mycotoxins. “Last year we were seeing a combination of different mycotoxins, but they were showing up at below-regulatory levels, so it became a co-occurrence issue,” Kern-Lunbery explains. “There would be low levels of aflatoxin with another mycotoxin, and at those low levels, while each individual number says that it’s safe to feed, when they’re occurring together, they have an additive effect that’s detrimental to animal health.” Mitigation There are products on the market that can help inhibit mycotoxins in feed in two different stages. There are mold inhibitors that help to reduce the amount of mold that grows on crops after they have been harvested, preventing mycotoxins from developing. There are also products designed to utilize
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