I think there are some little things that can be done to reduce breast sores, bad legs, and maybe even heart troubles.
I'm just working on these so don't know if it works or not, but so far so good.
1 keep the food high so they need to stand up to eat, no laying in the feed or on the floor stuffing their faces
2 put feed and water a good distance apart so they are forced to move some
3 start with higher 22 plus % feed and then back it down over the first 4 weeks, giving them a good kick start with more expensive feed in the first couple weeks does not cost much as they are eating less to start.
4 like others said keep a limit on the food. So far, this batch I am feeding twice a day about 12 hours apart and try to figure the feed so they run out a couple hours before next feeding. Left without feed for 12 hours they get pretty rangy and trample each other to get the first crumbles that hit the feeder.