Two quick comments after reading the treats chart:
Banana peels have a nice layer on the inside that the chickens will peck off, high in potassium. They do not eat the outer skin, and these can be picked up and disposed of at a later time if the deer don't eat them first. Next time you eat a banana really look at the peel and you can see the edible layer, the riper the banana the softer this layer is.
My #1 chicken treat is not on the chart! It is Okara, this is the highly nutritious soft meal that remains from soybeans after making soymilk. It is high in protein and calcium and has a taste that chickens go bonkers over. I know it isn't common here in the USA, but it is a serious contender for best chicken treat.