I have 20' stave silos that I store corn silage in.  They are sometimes covered with plastic for almost a year before I start feeding out.  Mice get up there and chew holes in the plastic with predictable results.  Last year after covering the silage I put several packs of mouse bait on top of the plastic to no avail.  This year I sprinkled a liberal dose of proprionic under the plastic before covering, I don't know if that may deter them or not.  Anyone have any tricks for discouraging mice?  They have 300 ton of silage I don't know why they think they need to chew the plastic to shreds.