Wet haylage?... watch for clostridial fermentation

Mike Rankin
Crops and Soils Agent
University of Wisconsin - Extension

            With the amount and frequency of rain we received during the first crop harvest season, it's likely that more than one load went into storage at a higher moisture content than desired.  This can be a cause for concern.  In alfalfa silage that is less than 30 percent dry matter, clostridial fermentation can occur.  Clostridia are anaerobic (no oxygen required) bacteria that convert forage sugars and organic acids in butyric acid, carbon dioxide, and hydrogen gas.  The result is excessive dry matter and energy losses in a silage with a high pH (typically over 5.0).  After fermentation, the silage is easily recognizable by its rancid milk or sour odor.

What are the consequences of feeding clostridial silage?

The feeding value of silage that has undergone clostridial fermentation is greatly reduced.  The high butyric acid level can be harmful when fed to transition cows as it can lead to subclinical or clinical ketosis.  Clostridia also degrade proteins, releasing ammonia and amines.  They also produce high levels of acetic acid.  Normally, we like to see a lactic acid to acetic acid ration of at least 3:1.  That won't be the case with clostridial silage.

Some forage testing labs offer a fermentation profile test.  It provides the levels of volatile fatty acids (lactic, acetic, butyric, and propionic acids), ammonia, nitrogen, crude protein, and pH.  This can be a good tool to assess silage quality.