Oxygen is the enemy of good quality silage.  Aerobic (oxygen loving) microorganisms cause the deterioration of carbohydrates in silage, leading to spoilage and mold.  Whenever silage is exposed to air, quality begins to decline.  When feeding from a silage face, how much silage should be removed each day to maintain silage quality?  I recently read an on-line article from Dairy Herd Management that said oxygen has been measured up to 3 feet behind the silage feed-out face in well packed bunkers.  That data suggests that feeding two to three feet/day off the silage face may be ideal.  The entire article is available at: http://tiny.cc/dairyherdmgmtsilagekeys.