It's true too much protein can damage you kidneys, not sure about liver.
But it can cause gout as well as kidney failure.
Too much... being a figurative term. Because what's too much for one may be just right for another and vice versa.
I used game bird feed at 28% protein with my first set of chicks because the feed store swore by it. Come to find out feed store employees are often limited in their knowledge and only repeating what they've heard. I always suggest a second opinion if that is where the information came from. And to be honest even people who I trust and respect, I think you should get a second opinion. Sometimes people just don't have all the information.
So also, if someones birds die and they don't have a necropsy done... they might not know there was organ failure or what was the cause of death and they can only assume. The organ failure and kidney issue can also be cause by too much calcium (another type of gout) as in layer feed fed to non layers like roosters, chicks, or molting ladies. Some people will feed this way and never see an issue. It may be an issue only if the individual bird is somehow predisposed to a problem.
My guess as to why he claims show birds need more protein is because feathers are 90% protein... so you will likely get glossier and better quality feathers from the higher protein. Also, heavier breeds can benefit more from higher protein than the light breeds like leghorn or RIR. They have smaller body masses to maintain as well as usually less feathers. I decided that although I like more protein than layer... that game bird might be too high. So I go with flock raiser which is 20% protein and OS on the side.
Also, I read studies showing that the problems in broiler type birds were decreased by decreasing the amount of protein if their starter feed to slow their growth rate. And when I had a large breed dog the vet told me to get a feed to slow the growth to prevent later problems in the joints and bones. I though the vet was crazy. But the more I learn, the pieces seem to fit.
One reason I go with the flock raiser is I have chicks, pullets, cockerels, molting hens, breeding (hatching) hens all the time. It is a happy medium for me. Not that I think it's perfect for all in my flock (20% is less than 22% starter), but the best choice I have available with my current information.
Though I wish I could agree with that Purina post, and I mostly do... they don't account for your individual practices. Like whether you free range or give treats. And as far as I am concerned the 16% in layer is the bare minimum needed to maintain a birds body and laying... not hatching the healthiest and most viable chicks. And boys need more protein to develop and maintain their muscle than girls do. Plus another poster had to correct them about their own products just above...
I am no expert... but I don't have a product to sell either. I have 50+ birds and 6 years raising them. Only sharing my personal experience with you. I will agree that balance is key, even if I don't agree with what that balance may or may not be. We all have to do what seems right to us. And we all have different purposes for our flocks. And those may change over time. My understanding and preference has changed many times. I used to feed exclusively layer... but will never feed layer again. Not because it's bad but because it isn't right for my flocks needs, IMO.
I do use Purina products because that is what's readily available (even though they are sold under different brand names). To me name has no bearing and what's important are the nutrients but also I prefer to go with which ingredients sound the best... and quit using Purina flock raiser because they started adding DE to it and I don't want to breath it. Ever see the big cloud when you pour a bag of feed? Breathing dust is one thing DE is a whole other, The other product by them under a different name has the same first half of ingredients with almost identical nutrient values but no DE and $1 cheaper for a slightly less pretty bag. My point being, even if you find a product you like beware they change the formulation sometimes without saying anything. And I don't like vagueness. I rather see it say wheat or corn but if it says grain byproducts... sorry not my cup of tea.
And yes, the higher protein products always cost more. Because corn, and oyster shell are cheaper to produce than protein.
You are correct, most chickens get between 16% and 22% depending on life stages. That guy you saw had special needs and goes with what seems to work for them. Would be curious to know their age of mortality as well as other things like chick vitality and hatch-ability as well as if they ever do necropsy and see how the organs were holding up type thing.
Anyways, even if his needs were different ... god looking out for your fellow poultry keepers!
There maybe people who are just doing what the feed store told them. So don't hold back your info next time either... you just might save a life!