All my chickens are fed milk (soured as kefir) to make up a full home-mixed diet. Other ingredients are sprouted wheat, sprouted corn and sunflower, alfalfa, soy meal and minerals (kelp, salt, shell grit).
Layer hens don't really want much milk (whether soured or not) because the high phosphorus-to-calcium ratio can cause soft shelled eggs. But I find the chicks do really really well on a diet with a fair bit of soured milk and it seems to help against cocci (combined with gradual exposure).
Best wishes,
Erica
Edit: oops, also they get fresh garden greens and a treat of liver or other meat about once per week.