Mycotoxins are invisible poisons produced by certain moulds, and their effects on livestock may be far less obvious than spoiled feed or a visibly sick animal.
Dr. Alexandra Weaver, who provides global technical support for Alltech Technology Group, told a recent feed-industry webinar that animals commonly consume several mycotoxins at once. Research on United States corn found that more than 90 percent of samples contained two or more mycotoxins, with an average of 4.8 mycotoxins per sample.
That matters because toxins can work together. Weaver described an additive effect as one plus one equalling two. A synergistic effect is more serious: one plus one may act more like five because several toxins attack similar parts of the body.
The digestive tract is first exposed when an animal eats contaminated feed. Even low concentrations, consumed over time, can damage the gut’s structure, weaken its natural defences, and upset immune balance. Mycotoxins may also affect internal organs, hormones, behaviour and reproduction.
High toxin levels can cause clear illness, but Weaver said chronic, lower exposure can be especially troublesome because the signs are easy to miss. Animals may simply eat less, gain more slowly, convert feed less efficiently or fail to perform as expected.

The losses can be direct or indirect. A toxin can directly damage proteins, DNA, organs, or intestinal tissue. Indirectly, a weakened gut or immune system can leave an animal more vulnerable to disease, reduce its response to vaccination and increase veterinary costs. Offspring health may also suffer.The result is often a costly production problem with no single obvious cause. A digestive disorder, reproductive difficulty or unexplained performance decline may involve mycotoxins, another farm stress, or both.
Species also respond differently. Josh Teulker, technical support with Alltech Technology Group, explained that the same test result may represent one level of concern for poultry and a different level of risk for pigs or dairy cattle. The toxin level alone therefore does not tell the whole story. Producers must consider which animal will eat the feed and how much of the affected ingredient is included in the ration.
Testing only for one familiar toxin can also create false confidence. Weaver reviewed corn samples from the 2021 through 2025 harvests and said testing only for aflatoxin would have missed most of the potential risk in that data. Testing only for deoxynivalenol, commonly called DON or vomitoxin, captured more, but still underestimated the total risk.
Alltech’s approach combines results for several toxins into a risk-equivalent quantity (REQ). In plain language, it turns multiple test readings into a single overall risk measure tailored to the animal being fed. That can help feed mills, nutritionists, veterinarians, and livestock managers judge whether a sample presents a low, moderate, or high level of concern.
Teulker stressed that mycotoxin control remains one part of a comprehensive feed safety and quality program.
Weaver recommended being proactive: test ingredients and finished feeds, track results, watch animals carefully and note other stresses that could worsen their response. Knowing what is in the feed before performance falls gives managers more options to segregate grain, adjust rations or use an appropriate mitigation strategy.
The practical lesson is simple. Mycotoxins can quietly turn valuable feed into poorer animal health and lost income. Understanding the combined, species-specific risk is the first step toward protecting both livestock and the farm’s bottom line.
Weather does more than influence crop yield. Heat, drought, excess rain, and crop stress can also affect where mycotoxins occur, making testing increasingly important for feed mills and livestock producers.
Dr. Jan Dutton, CEO of CropProphet, shared at the same webinar that weather can either support or suppress the fungi associated with particular mycotoxins.
Dutton used aflatoxin in corn as an example. Temperature and moisture during silking are important, so CropProphet combines county-level weather information with United States Department of Agriculture silking data. The resulting maps show where weather indicates low, moderate, or high aflatoxin risk.
For 2026, the United States corn-growing season was wetter than normal, but a warm, dry stretch ran from about July 9 through the end of the month. Dutton said differences matter because corn does not silk at the same time in every state.
Long-term change is also shifting expectations. Asked whether aflatoxin risk so far north in the United States is typical, Dutton said warming temperatures are making northern risk more typical, as temperatures during key crop stages are a major factor.
Weather maps are useful for deciding where to look, but they cannot replace sampling. A forecast shows the likelihood of trouble; a grain test shows what entered the truck or feed mill.
John Bielecki, regional product manager for North America at EnviroLogix, said a sound program begins by identifying ingredients that carry high risk or make up a large share of the ration.
The greatest testing error often occurs before the test begins. Mycotoxins tend to collect in pockets rather than spread evenly throughout a load. One small scoop may therefore miss a hot spot or exaggerate the condition of an entire truck.
Bielecki recommended probing a truck at several locations and collecting far more grain than the final test requires. The larger sample should be mixed, divided and ground before a small portion is tested. That small portion must represent roughly 56,000 pounds of grain, making careful sampling essential.
Kasey Kerperin, territory manager at EnviroLogix, said repeatable procedures help different employees produce results that can be trusted. Rapid testing can support decisions upon receipt, including accepting, rejecting, or segregating a load. Results collected over time can also reveal patterns involving suppliers, growing regions or particular ingredients.
Testing should lead to a plan. A mill may buy from a lower-risk area, change testing frequency, separate higher-risk grain or adjust its use in feed. Periodic laboratory checks can confirm that an on-site program is working properly.
Technology can help turn numbers into decisions. EnviroLogix’s system can transfer rapid test results to Alltech’s RAPIREAD platform. That system interprets the findings based on the livestock species being fed, because the same toxin concentration can affect poultry, pigs, and dairy cattle differently.
Dr. Alexandra Weaver, global technical support at Alltech Technology Group, said weather and risk maps often align well. However, storage remains another point of danger. Poor moisture control can allow a manageable problem to worsen after harvest.
Changing weather means last year’s testing plan may not fit this year’s crop. The practical response is to use weather information to focus attention, collect representative samples, test consistently and keep records. Climate signals can warn where mycotoxins may develop, but disciplined testing tells producers what they actually have and supports safer purchasing, storage and feeding decisions. •
— By Harry Siemens