I'm a relative newbie to chicken nutrition and care, but have been feeding rabbits for some 25 years and am pretty good at rabbit nutrition.
What I've been doing with my chickens is to try and get away from that gawdawful protruding keel; while I'm not looking for commercial broiler feel, I'm looking for a reasonable amount of muscle and overall condition rather than feeling like a feathered skeleton, which is what a lot of free range chooks feel like around here.
I recently cooped my chickens to save my landscaping; I'd like to have a yard again!
So they are now getting a much more controlled diet, and I can see some improvement. I give a varied supply or mix, depending on what I can afford, of:
Nutrena's newish minipellet with oyster shell and cracked corn;
Dove & Quail mix of whole seed/grain;
Dog food (Costco--the pellets are small enough to eat easily and there's plenty of oils and highly palatable);
Bread from the day-old bread store--if I can get the feed type, it's a lot cheaper and quite varied in types--if not, I just get what's cheap and whole-grain
Whatever scraps I have that I think they'll eat;
The neighbors' veggie scraps, which they put over the fence for the chooks (they get eggs in return, so it seems fair LOL)
As a very occasional treat, I'll buy mealworms, but would rather just dig in my compost pile for redworms.
I try to keep it as varied as I can, which they seem to appreciate, and within about 16-25% protein range with plenty of calcium available..
Suggestions are always welcome.