Avoid these dangers of overfeeding your flock 

I have kept chickens for over 40 years (on & off, mostly on). So buckle up (:P), you need to keep the chickens occupied with other things and make them forage. Give them a big area to roam/forage over. The biggest killer is putting chickens in a small wired pen! They have nothing to keep them busy, so they just eat and feather peck, etc. I have a feeder (the type where they stand on a platform that opens the feeder - keeps rats away) so my hens can get feed ad lib but they do not over eat, they have a large area with grass and earth. They spend MOST of their time foraging. Another tip: use Diatomaceous Earth as an emulsion with water to paint the inside of the hut, it controls mites, also dust the nest boxes.