Chickens will eat just about anything. In a pinch give them variety and let them choose: fruits, vegies, grain. I have supplemented wild birdseed when I'm low on feed since a run to town is about 30 miles!
Be sure to toss in some protein: a can of tuna, leftover meat of any kind. I ran out of food on Christmas eve, and my feed store is normally closed on Mondays. I defrosted a pound of ground meat, and cooked that. Added some uncooked oatmeal, cooked rice, and a couple handfulls of birdseed & scratch. Didn't seems like enough for 2 days, so I added a can of mackerel that had been in the pantry for who knows how long.