The squirrels chewed right through the lids. I caught it before they got holes large enough to get in there. And luckily my feed didn't get wet. They only bothered the feed not my DE, PDZ, or Sand barrel. I caught them in the act. Yes the lid twisted around so it couldn't be taken off by a large ( raccoon) animal. I don't worry about squirrels attacking my chicken I worry about them starving them.

I suppose I should have mentioned that the animal feed here gets kept in something like a larder attached to the house.

I don't keep feed in the coops or anywhere outside for the reasons you've mentioned.
I do catch the occasional mouse though.