Wild Yeast’s Effect on Milk Production and Components

Posted: February 26, 2020 | Written By: Brant J. Groen, Form-A-Feed

wild yeast

It is every livestock farm’s desire to feed high-quality corn silage, high moisture corn and/or earlage to ensure excellent animal health and production. Did you get your corn silage or high moisture corn put up under ideal conditions this past fall?  I’m guessing for most of you the answer is “NO.”  With the crazy fall harvest season, there are now concerns of the feed not performing as well as expected.  Also, there is discussion out in the country of some farms having lower butterfat than desired.  One of the issues present on some farms this year is wild yeast in corn silage, earlage or high moisture corn.

Wild yeast facts:

  • Well preserved feeds have yeast counts <10,000.
  • Under the right conditions yeast will double every 2 hours. Conditions include:
    • Loose feed
    • Warm temperatures
    • Setting in TMR or bunk
  • High yeast counts are indicative of aerobic environment.
  • Crops with a high concentration of starch will have a tendency to have more yeast issues.

Wild yeast impairs rumen fermentation:

  • Wild yeast reduces nutrient availability of affected feeds and impairs rumen microbial fermentation.
  • Wild yeast, molds, and undesirable bacteria in the feeds can interfere with the populations and activities of normal rumen microbial bacteria and reduce fermentation.
  • Decreased rumen microbial activity reduces the energy and microbial protein available to support milk and milk components.
  • Microbial stability concerns can magnify stress conditions for high producing cows with suppressed immune systems.

How feeds become unstable:

  • High yeast populations are ensiled at the time of harvest.
  • Once the oxygen has expired in a properly stored environment, the yeast has become dormant.
  • At feed-out the yeasts are re-energized by the introduction of oxygen.
  • Yeast growth becomes exponential, consuming lactic acid.
  • Excessive heat is produced, creating an unstable, unpalatable feed.
  • As the lactic acid is consumed and volatilized, the silage pH rises.
  • Molds prefer the higher pH and begin to grow very rapidly.
  • This results in massive spoilage.

Possible reasons why wild yeast is more of an issue this year:

  • Ensiled drier, resulting in less compaction. This is more of an issue when corn silage is ensiled at 62% moisture or lower.
  • Less compaction due to less starch (light test weight).
  • Cooler temperatures at ensiling leading to poor fermentation (or no fermentation at all).
  • Wet weather, rain splash before harvest.
  • Slow filling due to weather conditions.
  • Poor covering or not covered soon enough.

Basic problem with wild yeast:

  • Deterioration of nutrients
    • It is estimated for every 400,000 yeast count, feedstuffs will lose 1 point N.E.L or 1 point N.E.M.
      • Robs starch, sugar, protein
    • Yeast converts components of the silage to products that have little or no value for feed preservation or at feed-out. Example – ethanol in high moisture corn.
    • Yeast lowers acetic & lactic acid production and increases silage pH.
      • This allows for bad bacterial growth & mold.
    • When the silage ferments longer than normal time – this is a good indication of high yeast feed.
    • When feed heats quickly in the bunk or at silage face – this is a good indication of high yeast feed.

Effects of wild yeast on cows:

  • Lower feed intake.
    • Reduced NDF digestibility
  • Decreased milk production.
  • Lower butterfat test than normal.
  • Inconsistent manure.
  • Sporadic digestive upsets.
  • Possibly more mastitis & other health issues.
  • Potential for more fresh cow issues.

Corrective measures for high wild yeast counts:

  • Nothing we know of today will fully correct the issue once you have it. We must prevent it.
  • Quit using (or dilute) problem feed.
  • Maintain very good smooth silage face.
    • Don’t buck directly in face with loader.
  • Taking 12”/day off face.
  • Cold weather usually helps, but not always.
  • Use a top end inoculant or acid at harvest is very helpful
  • Add the maximum level of sodium bi-carb.
  • Add good yeast (Stealth 5)
  • Add App-A-Titeto provide a unique blend of flow agents, antioxidants, and B-vitamins to minimize losses due to these conditions.
  • Add a good DFM, which is usually quite helpful

If you suspect that your farm is dealing with high wild yeast counts, please contact your local Form-A-Feed Nutrition and Production Specialist to help you develop a plan to reduce its effects on your herd.


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