Who were these specifications developed for. My guess, the commercial factories where the primary concern is cost. I would only view them as absolute minimums and not representing healthy minimums.
Starter = 20% protein
Gamebird Starter = 24% protein
Grower = 16% protein
Finisher/Developer = 15% protein.
Strange, it won’t let me quote your entire post. Anyway cut and paste works.
Who were these specs developed for? The commercial operations whose primary concern is profit, not just the cost side. As anyone who deals with animals for a profit knows sick underfed animals do not produce very well. I do not treat my chickens the same as the commercial operations in many ways, but I do not assume they are keeping their animals poorly fed. That would not be profitable. They have developed a feeding regimen that keeps their flocks healthy and productive while watching the cost side. They’ve also developed specific feeding techniques we don’t use.
The big commercial laying operations use hybrid pullets as specialized in converting feed into eggs as the hybrid broilers are specialized in converting feed to meat. You can cause problems in broilers by overfeeding them. You can cause problems in the highly specialized hybrid layers by overfeeding them. That’s why I specifically mentioned the commercial operations and their chickens in my other post. Just because our chickens can generally handle more protein does not mean theirs can.
But too much of a good thing is often not a good thing. You might want to read up on avian gout, caused by too much protein in chickens. Excess protein has been shown to cause a hen to release more than one yolk a day to form an egg. If those yolks are released at the same time you might get a huge double yolked egg. If they are released separately you might get a deformed egg since two eggs have to share the shell gland at the same time. Often there is not enough shell material in the shell gland for two eggs in one day so the second egg is soft-shelled or very thin-shelled. Those eggs can easily be broken in the nest.
Higher protein levels mean the eggs will be bigger. Nice, right? My wife gave natural birth to a 10-1/2 pound baby. She also had two at other times that were in the 8 pound range. She admitted the process was a little easier with the smaller babies. Increase in egg size due to higher protein foods may not be that dramatic but I avoid feeding in the really high protein levels and mine forage for a fair amount of their food. I’ve never had one of my hatchery hens or hens bred from them prolapse, internal lay, or become egg bound. Coincidence? If you want to think so.
We all do things differently. We have different goals and different management techniques. I personally choose to not feed high levels of protein to my flock for my own reasons, except for young chicks. A lot of people do it and are very happy with the results.