I'm gonna go ahead and beg to differ,

Please let me tell you what my brain says... If peas are 77 calories and the protein from them is 18 calories... Don't birds eat to meet their caloric (energy need) and not a certain volume or weight per say? So 18/77 calories being protein would make that about 23% of the total calories coming from protein. PLEASE correct me if I'm wrong?
That being said if feathers are made from 90% protein, slowing down their growth by reducing overall growth *could* prevent angel wing. Reducing protein and increasing carbs might slow the growth of muscle and add fat instead (I don't know for real). I would suggest using a lights out routine... IF that works for ducks, I put my feed up at night and did so when I raised them. Yes, I realize chickens and ducks have different nutritional requirements... all information I gave was relevant to ducks, I think.