The broad-breasted birds are a special situation. Most people recommend feeding the heritage birds 22-30% protein during the first 8 weeks, then decreasing it down to 20-24% until 14-18 weeks, then the recommendations are all over the board. But the BB birds grow SOOOO fast and SOOOO big that you are more likely to have problems with the high protein. Keeping their protein levels at a more moderate level will keep their growth rate at a more reasonable level, so you're less likely to get leg problems and heart problems prior to slaughter age. If I personally were to grow out a BBB, I would feed it somewhere between 18-22% protein the first 6 weeks, then 16-20% thereafter, depending on my desired slaughter date, and how the bird was growing. But everyone feeds a little different, as there are hundreds of ways to manage these birds.
