If it is "old and got wet at some point in the past", I'd say toss it out to the garbage man. But, my girls think wet feed is the best treat on earth! Where their feeder sits right now (still a chick feeder because I just can't justify spending $30-40 on a huge container for 3 birds) it gets dripped in by my plant watering system from the deck above. It doesn't create a huge mess, but does soak about 1/4 cup of feed every other day. The girls go absolutely bonkers over the wet feed!
So, the point of my ramble....if it is "older feed that "just" got wet", let the chickens go hog wild eating it, and then go back to the "healthier" feed tomorrow when they've cleaned up all the old stuff.