I'm in the same situation, and without thinking I already froze some of mine when I bought it. the rest I keep in a 5 gallon bucket with the lid closed, if I need more I fill a gallon ziplock, and take it out in that much at a time.
I've frozen my parrot food for years, so I figured why not freeze it? I only have two chickens, and there is NO way my bantam hens are going to go through 50lbs in a timely manner.