Controlling molds, mycotoxins, and wild yeast in forages

As the winter feeding season moves along, we are now reaping the benefits or dealing with the challenges from last year’s crop. Now is the time to take time to evaluate and make plans for next year’s forage season and crop plans. Many of you will test soils and work with your agronomist to plan a strategy to meet your grain and forage operational needs. It’s also an excellent time to evaluate your forage preservative program and whether the program/product you used met your goals and objectives. This is also a good time to test your forages for wild yeast and mold counts that may be adversely affecting your herd.

Molds, mycotoxins, and wild yeasts are a major cause of nutritive loss in your feeds after it is harvested, and this loss can grow exponentially under adverse conditions. The presence of molds, mycotoxins, or yeasts in feed can cause intake problems, reduce production and components, and be a major contributor to animal health issues such as breeding and somatic cell issues. Yeasts require water and oxygen for growth. Molds also require oxygen and certain temperatures for growth. Temperatures over 70 degrees favor the growth of Aspergillus and temps under 70 degrees favor Fusarium.

The common ingredient during fermentation that is required by molds and yeasts for growth is oxygen. This is important because most bacteria based inoculants have very little effect in reducing the formation of molds and yeasts while oxygen is present. Mycotoxins are by-products of molds.

The most common question from dairymen is “How much does it cost to treat a ton of forage with your product?” The answer is: the cost to treat a ton of forage is high if the product is not designed to accomplish your objectives and get the return that you expect from the use of the product. More appropriate questions would be:

1. What can I expect as a return on investment by using your product in my forage harvesting program?

2. What is your product’s mode of action?

3. How does your product prevent the presence of harmful molds and wild yeasts?

During fermentation, when conditions exist where the level of acetic acid and lactic acid production is insufficient, harmful bacteria, molds, and wild yeasts will grow causing heating. When these conditions occur, mold and yeast counts can double every four hours. Utilizing Crop Cure® elevates the level of acetic acid, the first acid formed during the fermentation process and a precursor to lactic acid. This promotes a drop in pH to a level that reduces the growth of harmful bacteria, molds, and wild yeasts during the presence of oxygen. The increased level of acetic acid and lower pH also reduce the potential for heat damaged protein.

Common Complaints About Yeasts in Silages

  • Unstable silage in the silo and feed bunk
  • Reduced intakes
  • Acidosis-like conditions
  • Milk production and milk fat depression

Forage Analysis Report Card
This is a great time to do a fermentation analysis reviewing your volatile fatty acid profile compared to industry standards and your mold and yeast counts.

Interpretation Guidelines for Mold Counts



10 - 10,000

Relatively safe

10,000 - 100,000

Transition Zone

100,000 - 10,000,000

Caution Advised

Over 10,000,000

Feeding may not be


Yeast Counts
Yeast counts are a good indicator of unstable or hot silage. High yeast counts, greater than 1,000,000 may reduce aerobic stability to less than 40 hrs. Yeast counts greater than 1,000,000 may also have a negative effect on milk yield.

What product should I use to treat my forages?
When deciding which preservative to apply to your forages, some key factors you need to consider are:

  • effectiveness of the product and mode of action
  • return on investment
  • type of forage (hay, silage, baleage)
  • moisture level of the forage
  • storage structure being used
  • ease of handling of the product
  • storage and shelf life of the product

It is important to have a good understanding of all of these factors when choosing which product to use. If a product is not applied correctly or is used under conditions different than the label directs, you will not receive the results you had expected and the cost of the product will outweigh the benefits. Some products are specific to certain forages, moisture levels, and/or storage structures, while others may have limited shelf life and or may be messy and difficult to handle and apply.