Four Tips for Overcoming Wild Yeast Challenges in Forage This Spring by: Alltech


Despite the conditions we may currently see when we look outside, spring is here! As temperatures begin to rise and snow begins to melt, we need to keep watch for changes in our stored forages. As many will remember, the corn silage harvest last fall brought with it plenty of challenges. Most dairies have not yet experienced any of the issues that are expected to arise in their silage piles thanks to those harvest challenges — but spring will change that. As temperatures increase, wild yeast will begin to awaken in silages, leading to a decrease in forage stability, as well as the potential for issues with the total mixed ration (TMR) fed to livestock.

Last fall, high yeast levels were found in the fresh corn silage samples collected for the Alltech Harvest Analysis – North America (HANA). I have not seen many stability issues for silages yet, but they will manifest. As the warmer weather awakens the wild yeast, we will start to notice activity in our silages that was not present during the long, cold winter. When wild yeast is active in silage piles, it begins to feed on the energy from the corn silage, decreasing the energy available to livestock. Wild yeast can create many issues for a dairy, from decreasing forage stability to causing rumen upset at feeding. Additionally, the silage will begin to warm, leading to an increased pH and spoilage on the silage face, top and sides of the pile or bunker. This is especially true when Mucor and Penicillium molds are present.

If these changes go unnoticed in the forage storage unit and the silage is fed, symptoms will begin to appear in the barn. Common symptoms of active wild yeast being fed in silage include inconsistent and loose manure, decreased dry matter intake (DMI), a downturn in the farm’s butterfat test and, of course, reduced milk production.

Wild yeast has a negative impact on rumen function and cow performance. When this happens, I am often asked, “What can we do about this?”

Common symptoms of active  wild yeast in dairy:

  • Loose, inconsistent manure
  • Decreased butterfat
  • Decreased milk production
  • Decreased dry matter intake


First, evaluate and address the issues and concerns at the silage face. Whether your corn silage is stored in a silo, a bag, a bunker or a drive-over pile doesn’t matter; if the environmental conditions allow for it, wild yeast and spoilage can occur in any storage unit. If you think wild yeast is present, my first suggestion is to test the feed through a local lab, as this will give you clear answers about the levels and the specific types of contamination you are facing.


The next step is to evaluate the silage face, looking specifically for any visible signs of heating or spoilage. This can be done by the producer and nutritionist, but an Alltech on-farm representative can also help identify any potentially concerning signs by using a thermal imaging camera. If any heating or spoilage is detected, an improvement in face management will be necessary. This can be accomplished by increasing removal rates from the face and keeping the face smooth and clean by using a facer. I have personally seen many producers not using their facer daily in the winter months due to the extreme cold, and while this is understandable, when the weather warms and becomes more spring-like, using a facer will be critical to minimizing the effects of wild yeast and spoilage.


Next, do not be afraid to discard suspicious forage and spoiled feed. I understand that producers do not want to be wasteful by throwing away feed every day, but if poor-quality forage is fed to our livestock, their performance will be negatively impacted.


Lastly, feeding a quality live yeast like YEA-SACC® can help livestock overcome the adverse effects of wild yeast. Yea-Sacc bolsters the rumen by modulating the pH, scavenging oxygen, eliminating stress brought on by the wild yeast strains and enhancing overall rumen function. These benefits keep livestock performance on track and allow the animal to utilize the forages efficiently.