Common Fermentation Problems

Callie Courtney, Dairy and Forage Specialist, Purina Animal Nutrition (563)880-3080

When we make baleage, corn silage or haylage our microbiology skills come alive to produce high quality feed for our livestock. As a biological system the fermentation process doesn’t always go as planned. While our great homegrown forage goes through fermentation microorganisms feed on sugars and soluble carbohydrates to produce organic acids such as lactic, acetic, and butyric. Having high amounts of lactic and acetic will lower pH and drives a good fermentation and preserves the feedstuff. Some key factors can inhibit the lowering of pH and drives a less desirable fermentation, moisture, chop length, packing, covering, and of course mother nature.

Having a great fermentation is important for 2 reasons

  1. )To preserve nutrients to optimize livestock intake and performance.
  2. )To minimize dry matter loss and spoilage at feed out, there is a 12-15% loss of dry matter with a good fermentation and much higher with a poor fermentation and spoilage loss as well.

We know what good quality feed smells and looks like, so what about those times when it doesn’t look or smell so perfect; what went wrong? The only way to get better is to learn from our mistakes and do a better job the next crop or the next year. Here are a few problems that we might smell and what might have caused it.

  • Rancid or Fishy Odor This is butyric acid resulting from clostridia contamination from soil. Clostridia silage can result from cutting or raking to close to the ground, soil from packing tractor tires, and splash from rain, or manure applied too late after the previous cutting. Butyric acid also commonly results from silage that is too wet (>65% moisture) As well as the rancid smell the feed may have a slimy sticky texture. Haylage can clump into “butyric balls”. Fermentation losses of non-structural carbohydrates are high so ADF levels can be high, and protein is degraded. Palatability, intake and digestible energy are low and livestock performance is poor.
  • Moldy or Musty Smell Moldy feed results in high dry matter losses as well as poor palatability and livestock performance. This spoilage is the result of aerobic (oxygen) condition from poor pack, slow filling, dry feed, poor sealing, and slow feed out or poor face management. If silage feels warm or hot microbial spoilage is still going on.
  • Vinegar Odor Acetic acid is more commonly known as vinegar. Lactic acid is the most desirable product of fermentation is produced more efficiently with the least dry matter losses. Too much acetic acid relative to lactic (Fermentation Ratio) means the fermentation was less than optimally efficient. Most times when using a L. buchnri inoculant you will have a higher acetic acid, this helps control wild yeast growth in corn silage and fermented feeds with corn in them. It also keeps feed cooler in the summer months and you will have a longer face life.
  • Sweet Odor This smell is likely high concentrations of ethanol produced by spoilage yeasts, mixed with acetic acid. Fermentation losses were likely high and this silage will be prone to heating and spoilage in the bunk. An optimum amount of lactic acid will have little smell.
  • Ammonia Odor This indicates excessive protein break down to ammonia and amines, which could be due to a clostridia fermentation or high pH.
  • Caramelized Odor This is heat damage haylage will be dark in color with a tobacco odor. In several cases it can smell burnt, indicating excessive heating. Heat damaged silage is the result of forage that is too dry. Protein becomes bound and is less digestible.

A tool I use on many farms that work with All American Co-op on the forage side is a fermentation analysis. This is a test that can be run at the lab when sending in samples; it will show you how much lactic, acetic and butyric acids are in the feed stuff. This can help gauge how well your fermentation went. 

Also to help drive a great fermentation it is important to use inoculants to help drive down the pH of the forage quickly to reduce dry matter loss. You pay to plant and harvest the crop; let’s keep more of it as good feed for livestock, not throwing spoiled feed away or having it disappear through dry matter loss.

All American Co-op has top of the line inoculants that can fit anyone’s needs, call and order yours today!!!! Find Links to all of the inoculants we carry; including Biomax Pro, Silo Solve MC, Silo Solve AS, Silo Solve FC, and Silo Solve OS, on our webpage at

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