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Manage your mycotoxin load

Don Giesting for Progressive Dairy Published on 01 October 2020

Last fall was particularly difficult for forage harvesting and post-harvest management. Weather impacts have created major problems for forage management; among these challenges, mycotoxins can be a costly and sometimes hidden risk.

When conditions are right, mycotoxins don’t only impact feed safety but also food safety. While forage producers cannot control temperature, rainfall and humidity, they can influence some other factors involved in mold growth and the potential for mycotoxin production. This article will discuss testing and management best practices that can help when dealing with mycotoxins.



Molds are nearly everywhere, with the most commonly found mycotoxins coming from three major mold families: aspergillus, fusarium and penicillium. Molds produce spores that are able to remain viable for future development if the present conditions are not suitable for them to grow. Molds can only grow when they can access favorable nutrient supply, temperature and moisture. When in these favorable conditions, molds enter a vegetative state to grow.

Therefore, while there may be mold spores throughout a field, not all areas of the field will be under stress. When and where crops may be challenged by temperature, pests, wind, rain or hail, these can cause additional stress for the plants and enable the production of mycotoxin development. The correct mold growth conditions combined with an external stressor create the perfect environment for mycotoxin production.

Mycotoxins in field and forage

Due to their high moisture content, fermented forages tend to create some unique challenges for producers. Most forages naturally contain enough moisture and nutrients to support mold growth; therefore, as mentioned above, contamination can occur in the field and further develop post-harvest. The key to reducing mold and mycotoxin issues in fermented forages is to limit the amount of oxygen present. Molds only grow when oxygen is present, so post-harvest toxin production can occur when packing and sealing are delayed or inadequate. Rapid and effective processing, packing and sealing of silos is essential.

Managing toxins in the field produced before plants are harvested can’t only be described as difficult, but nearly impossible. As was the case this past year, molds grow and produce toxins with little opportunity for grower intervention, which increases the need for proper testing for toxins. Part of the difficulty in determining mycotoxin risk is: There will be areas in the field or in storage that have high levels of mycotoxin contamination and other areas that will have much lower levels of mycotoxin contamination.

Testing for mycotoxins

Reviewing historical mycotoxin reports to understand what is typical in your region and observing survey results can be insightful. However, to truly understand what is happening in the ingredients going into your operation, you will need to submit samples of your own.


When grain or other plant-based ingredients are harvested and processed, they may become inadvertently mixed with forage that has varying amounts of mycotoxins. To best understand the effects of this inconsistent contamination, take multiple sub-samples from throughout the field or storage facility. Be sure to use good sample mixing to establish representative samples to analyze for mycotoxins.

Sampling recommendations

  • Be sure to follow proper safety protocol while collecting samples. Remember, no job is so important that it can’t be done safely.

  • Take samples across the face of the bunk (top, front, sides, bottom), gathering material from the different locations to equal about a 5-gallon bucket when combined.

  • Mix up your samples and then take sub-samples to compose roughly a gallon bag of sample. If there is spoilage in one area, you can take a separate concentrated sample from that area to submit individually to determine which specific molds or mycotoxins you are dealing with.

  • When taking samples, take all samples at the same time of day and ship to the lab as soon as possible to get the most accurate results.

Best management practices

Manage forage as the high-value ingredient that it is, making sure no corners are cut that could increase the opportunity for mold or mycotoxin contamination. While no animal diet can be guaranteed to be free of toxins, these key principles can be applied to reduce the risk and impact of molds and mycotoxins.

  1. During warm weather feedout or when mold and mycotoxin risks are present, apply a blend of organic acids to combat any additional mold or yeast growth.

  2. Avoid or reduce addition of visibly mold-contaminated forages to the TMR.

  3. Stressed animals and youngstock are most at risk; limit exposure of these animals to suspect feeds.

  4. Carefully observe animals getting suspect feed and dilute as much as possible.

Managing your forages and diets to minimize the impact of molds and mycotoxins is 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 frequently throughout the harvest season and periodically in warm weather during feedout for toxins likely to be a risk to your business.  end mark

Don Giesting
  • Don Giesting

  • Micronutrition Innovation Lead
  • Cargill Animal Nutrition
  • Email Don Giesting