Chickens won't eat their feed anymore

I've been giving my chickens Barale poultry feed for a few months now, and now they won't eat it anymore. They just dig through it and then leave a mess of food everywhere. I also noticed they try to eat the cats dry food I leave out for them. I usually have it separated but occasionally the chickens sneak through the gate I have separating the hill and they dig in. Are my chickens tired of their food, should I finish the bag I already bought (which is 3/4 full still) or change their food? Thanks