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OSU Extension

College of Food, Agricultural, and Environmental Sciences


It is easy to see the importance silage plays in ruminant livestock rations by observing the number of bunker silos and silage piles that are on area farms.  Feeding out that stored silage requires management.  Silage management can be discussed from two perspectives, one being how to manage the removal of silage from the silo to maintain silage quality and promote animal intake and the other on how to keep farm workers, family, and visitors safe around the bunker.

The key point to remember is that air is the enemy of silage quality.  Once silage is exposed to air quality begins to decline.  The reason is that yeast begin to grow in the presence of oxygen and those yeast metabolize the lactic acid that was formed during silage fermentation.  That lactic acid keeps silage pH low, preserving silage quality.  As yeast metabolize the lactic acid, silage pH begins to increase and this allows fungi and bacteria to grow, which results in silage quality degradation.   After the bunker silo or silage pile is opened up and silage starts to be used, the goal is to remove an adequate amount of silage each day from the bunker so that the face of the silage remains fresh and silage quality is maintained.  In general, a minimum of 8-12 inches of width should be removed from the silage face each day.

Silage face management is important.  Bunker silos or silage piles that have poor face management, generally characterized by uneven and/or rough silage faces, will have a higher silage pH and higher temperature at that face surface compared to the silage maybe 2-3 feet behind the face.  Higher pH and temperature indicate yeast activity which results in silage heating.  The bunk life of this silage is decreased and dairy cattle usually eat a lesser amount of this type of silage compared to silage that is managed better.  The goal is minimize the penetration of air into the new silo face as silage is removed so equipment that allows a smooth face to be maintained is preferred.  Silage face shavers (or defacers) and silage rakes are designed for this purpose.  Digging into the face of the silage should be minimized because that usually creates a rough, uneven face with more potential for silage avalanches.  If a front end loader is used, do not dig into the pile from the bottom but rather remove silage from the top down, keeping the face smooth across the entire width of the bunker silo.  A smooth silage face reduces the surface area exposed to air, reduces the amount of water that may be caught and reduces the chance of a silage avalanche.

The top priority when working around a bunker silo or silage pile should be safety.  There are too many stories of silage avalanches occurring just after a worker has left the silage face or equipment betting hit by a silage avalanche, or worse, the tragedy of a person losing their life after being buried under a silage avalanche.  The first point in silage safety is to recognize that silage avalanches are real and there is no way to predict when and where they will occur.  Although  a rough or uneven silage face, or one that has been undercut, is more likely to have an avalanche, even  a well maintained smooth silage face could have part of that face fall away.  With the size of many of the bunker silos that we commonly see today on farms, those avalanches involve multiple tons of silage falling.  If a person is located below when that occurs, this can easily result in a fatality.

A few silage safety guidelines that should be followed include:

  • Never stand closer to the silage face than 3 times its height.  When a silage avalanche occurs, the silage falls down and runs out away from the silage face.
  • Do not fill bunker silos higher, or create silage piles higher, than your unloading equipment can reach.  These are the situations that most typically create overhangs when removing silage.  Generally most unloading equipment can reach 12 to 14 feet above the silage floor.
  • Follow the “buddy” rule and never work in or near a bunker or pile alone.  Suffocation is a major concern in the event of a silage avalanche and the minutes saved in a rescue attempt because of the buddy rule could mean the difference between life and death.
  • Use proper removal or unloading techniques.  Never dig the bucket of a loader into the bottom of the silage.  Do not undercut the silage face.  Shave the silage from the top down on the silage face and maintain a smooth silage face.
  •  When collecting a silage sample for quality analysis, do not sample from the silage face.  Collect silage in a loader bucket and sample from that loader bucket after it has been moved a safe distance from the silage face.
  • Consider posting a warning sign: “Danger! Silage Face Might Collapse” around the perimeter of bunkers and piles.

Reference materials used in this article include an eXtension article by Donna Amaral-Phillips at the University of Kentucky available on-line at: and the Silage Safety Handbook by Lallemand Animal Nutrition.   Other good silage management and silage safety references include: (Click on link)

Horizontal Silo Safety: Penn State Extension publication

Silage Face Management: California Extension publication