I have kept horse feed, which contains full grains, in metal trash cans. UNLESS you have a rat problem, the mice can't get to it. Just unloaded 500 pounds (10 fifty pound bags) of sweet feed yesterday, and I have the capacity to store 17 of them in my grain room.
ALSO, right after we moved here I cut a 5" x 12" "cat door" in my grain room, so as to:
1) allow cat access
2) give my kitties a safe place to go if chased by a predator
I always keep it latched bc a horse will founder if he/she has access to the grain.
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