I used real high protein the first 2 weeks (28% which was turkey starter) and then switched to chick starter (24%) for the remaining 6 weeks. All lived and the 8 week live weight was 8+ lbs (I think one may be 9+)
Chick starter for the first 4-5 weeks then broiler feed. 24hrs a day for first week, 12 hours for next 3 or so weeks and then they were free ranging so we'd go out and dump a pile of food several times a day, about what they could eat in 20 to 20 minutes. At 10 weeks they were 6-8 lbs dressed.
I fed chick feed and then switched to layer mash/whole grains when they joined the layer flock on free range at two weeks. I fed once a day each evening and butchered around 11 wks with live weights on average of 10 lbs.
I ordered my CX from Welp and here's what their site has re: feeding.
Start your Cornish Rock broiler chicks just as you start any baby chick. Start them on a 20-22% Chick and/or Broiler Starter. Keep them on that ration for the first 4.5 to 5 weeks. At that age, switch them to an 18% Chick Grower. Please make sure you restrict the feed as we outline below! Provide 3 inches of feeder space and 1 inch per chick of watering space.
You will "full feed" your broiler chicks around the clock for the first 5 days of age. At 7:00 p.m. of the 5th day, make sure your broiler chicks are completely out of feed. That means there is positively no feed from 7:00 p.m. of the 5th day of age until 7:00 a.m. the following morning. You want them out of feed for 12 consecutive hours. Water, yes, but no feed for 12 hours. Continue this "minor feed restriction" program, removing the feed every night, until time of slaughter. Failure to follow this feeding program may result in heart attacks. Sudden Death Syndrome or "flip" as it is sometimes called can result because of the very rapid growth of your Welp Broiler Chicks. Following the above restriction outline, religiously, every night commencing the 5th night of their 5th day of age, will reduce the "flip" thing substantially.
It seems that there are so many different feeding programs, and for us newbies, it can get all so confusing; just the protein issue is a science in itself - reading the forum one sees 16%, 20-22%, 30%, 18%, 28%, 19% - and that is just on the first page! LOL What is comforting is that so many report great results. Maybe this CX is a bit more flexible than we give credit. I'm about to find out I suppose."Yikes" it's kinda scary.