I feed them medicated chick feed for their first 4 weeks, since they don't have non-medicated in our area.  After the first 4 weeks I change to 
Manna Pro Gamebird/Showbird feed, at 24% protein.  I have a large fowl, heritage breed, so they are big, and slow to grow.  In the first year, the roosters are to reach a weight of about 9.5 lbs., and the hens about 6.5 lbs.  I find the higher protein helps them grow better, and develop out better.  Somewhere around 6 - 7 months old, the pullets begin laying.  That's when I change them to a grower/raiser type feed usually around 18% protein, or I give them layer feed, but occasionally boost the protein a bit with mealworms I raise for them, or with animal protein, or with eggs.  Again, I find a little higher protein while they're still developing that first year, is very beneficial, however, if the protein is too high after the pullets begin to lay, they don't lay as well.
I started with sex links, and I could start them on chick feed, then after 10 weeks put them on  grower, and layer feed when they began to lay.  Of course, they did not have to attain the growth, and development that my BA's do.  
During molt, I faithfully increase their protein.  I make sure that at least twice a week, they get an animal source of protein, not just vegetable from the feed.  Cat food, leftover meat, eggs, etc. work well.