• ZISK

Mycotoxins in Feed… Now What?

Sarah S News Team

July 1, 2022

Testing for mycotoxins is commonplace on many dairy farms. It may be performed as a proactive strategy like testing the new crop every year. Or it may be brought about due to visual changes in feeds, cow health, and from depressions in production and reproduction numbers.


Reasons for testing is generally related to some aspect of cow performance. This can range from reproduction issues such as aborts and abnormal heats to poor milk and milk component production. Depending on the toxin there will be different indicators that a farm may notice. For example, vomitoxin loads will cause the cows to spit up cuds, which often occurs in the fronts of stalls. While the mycotoxin zearalenone can be the origin of common reproduction issues listed above. Often a farm will experience a combination of these and other symptoms when mycotoxins are present at elevated levels.


The most common mycotoxins are aflatoxin, deoxynivalenol (also known as DON or vomitoxin), zearalenone, and fumonisin. Use this table when analyzing mold tests. Watch for key symptoms associated with each mycotoxin and note what feeds may be the culprit.


Mycotoxins have a 5 billion USD (US Dollar) estimated impact on the United States and Canadian animal industries annually. It is critical to understand the extent of mycotoxin challenges in feeds because almost any feedstuff can develop mycotoxins during the growing season, at harvest, or throughout storage. Further too, understanding your farms specific challenges based on climate, soil type, and weather. For example, cool, wet weather favors fusarium toxins, while hot, humid weather encourages aflatoxin formation. These characteristics can make fusarium toxins more prevalent in the Northeast and Midwest, and aflatoxins produced by Aspergillus more common in the South.



Still, feeds from several regions often are used on many farms, particularly in the grain-deficit areas of the Northeast and Southeast. While grains receive the most attention, byproduct feeds, protein concentrates, finished feeds, oilseeds, wet brewers grains, food wastes, and forages may also have mycotoxins. Regarding forges, whole-plant corn silage and haylage are more likely to be contaminated than dry hay. And, that heat-processing and ensiling do not destroy mycotoxins. Signs of mycotoxicity mimic those of other metabolic and infectious diseases, including ketosis, Johnes, BVD (Bovine Viral Diarrhea), Salmonella, and clostridial infections.


Now What? 5 Tips for Managing Mycotoxins


Test results came back positive… What can you do?


Managing your forages and diets to minimize the impact of molds and mycotoxins can seem like a full-time job. Remember that with mycotoxins, your best defense is knowledge. Gather information about what is happening in your area and, most importantly, sample and analyze often throughout the harvest season and periodically in warm weather during feed out for toxins likely to be a risk to your business.


Different mycotoxins will call for different approaches. Once you and your nutritionist understand what you are dealing with, there are multiple modes of action. In general, if counts are extremely high in certain feeds, diluting and limiting those feeds to at-risk animals is often necessary. More broad-spectrum actions can include adding gut health additives to a ration as well as including organic acids that inhibit yeast and mold growth. In our experience, a combination of feed management, immune support, and inoculants offers the most protection to cow health and production.


  1. Limit feeding to higher risk ingredients to most vulnerable animals. Based on your test results and the type of mold or molds, carefully observe animals getting the known contaminated feeds and dilute as much as possible. Stressed animals, youngstock, and reproducing animals are most at risk. For ingredients you can’t avoid feeding, dilution is the solution. Certain tactics for dilution can include separating and discarding fines, blending down with clean feedstuffs to reduce concentration, and piling silage after defacing and before adding to a mixer wagon.

  2. Support for the immune system. Mycotoxins, once consumed, often trigger an immune response, and suppress a cow’s ability to fight off infection and disease. The digestive tract and gut play a significant role in mitigating mycotoxins once in the body. Gut health additives such as a yeast and antioxidants (vitamin E, AOX, selenium) can boost the immune system.

  3. Feed a binder when aflatoxins are present. A mycotoxin binder is a substance that is added to animal feed in small quantities to trap mycotoxins, preventing them from entering the blood stream where they can cause serious harm to your animals. This process is known as adsorption and is a suitable strategy for aflatoxins, but it is not an efficient method to counteract, fumonisins, zearalenone, or DON. Therefore, we encourage using a mold test over a yeast count test for identifying and treating feeds and animals.

  4. Include organic acids in total mixed rations that inhibit yeast and mold. This tactic is especially useful during warmer weather and can help maintain feed quality in the bunk. A three-acid blend of acetic, benzoic, and propionic acids can help to control yeast populations and protect your rations against mold and mildew growth. This tactic benefits the feed in front of your cows by reducing nutrient loss due to yeast and mold growth and enhancing dry matter intake by lactating cows during heat stress.

  5. Prevention can be worth more than a cure. The most common route of mycotoxin exposure is through the consumption of contaminated feeds, making crop quality a critical factor in the development of mycotoxicosis in animals. Prevention starts in the field where molds are always present. It is as simple as understanding your crop and its environment. What is the proper soil nutrient profile for your plant? Is there opportunity to plant a hybrid that offers disease resistance. What management practices, like till or no-till and crop rotation, are being implemented?


While no animal feed can be guaranteed to be free of toxins, these key principles can be applied to reduce the risk and impact of mycotoxins. Proactively working with your nutrition team by gathering knowledge and determining a strategy for prevention and management can prove to be positive for cow health and feed cost.


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