Ill throw out my thoughts on this for people to laugh it or pick apart. Ill mention this lower down, but I do think we have a pretty wide range to aim for in how much protein they eat. And it is the amount of protein they eat in a day, not what percent in some of their feed. If you feed a lot of low protein treats, you can balance that out by feeding a higher protein feed.
For growing chicks, most articles about this say they dont need high protein levels. I think this is mainly a commercial consideration, why pay more for nutrients than you need. It is hard to sort out what is most economical from real health concerns. Some just say "high" protein can make them ill, but do not give the problems high protein levels can cause.
This is an excerpt from an article that actually explains the why a bit, with the link below.
Grower pullet rations. If youre raising young pullets to become layers, you want them to grow slowly enough to develop good strong bones and to reach a normal body weight before they begin producing eggs. High-protein diets tend to hurry the birds into production before their bodies are quite ready. Therefore, the ration for growing pullets, from leaving the brooder at 6 weeks to about 14 weeks, should be about 18 percent protein.
Developer or finishing pullet rations. At 15 weeks, its ideal to lower the ration to 16 percent protein. From 15 weeks to 22 weeks old or until they begin laying eggs, whichever is first, protein levels should be about 16 percent. The object is to get them well grown without too much fat.
http://www.dummies.com/how-to/content/how-to-choose-commercial-chicken-feed.html
I have read that high protein levels can contribute to gout in chicks and chickens. Not so much that it causes gout unless given in very high amounts, but if the chick or chicken have that tendency or already have organ damage, it can contribute. One treatment for gout in chickens is to reduce protein intake. Id guess that there are potentially other problems, but I could not find a specific reference. Id suspect that with feeding chicks or chickens, like adding nutrients to a garden, too much of a good thing is usually not a good thing.
http://www.scribd.com/doc/52660048/Presentation-for-Visceral-Gout-VG-in-Commercial-POULTRY
For adult chickens I dont have any specific links. I just did not spend any time looking for them and some of this is based on reasoning.
You can control the egg size to some extent by how much protein they eat. To a point, the more protein they eat, the larger the egg. There is a direct link from overly large eggs to prolapse and a hen becoming egg bound. Not that they have these problems each and every time, but the risk is higher with a double-extra-huge sized egg.
I dont know that I really agree with this one, but I have read that hens eating too much protein can cause the fat pad in their pelvic area to get too large, again causing egg laying problems. Id think this would be more likely caused by them eating too much high energy foods, but maybe high protein levels contribute.
Again Im not sure how true this one is, but Ive read that too high a protein diet can cause a hen to release more than one yolk a day, resulting in double yolkers or laying more than one egg a day. I do not consider either of these good. Aside from the increased health risk to the hen laying, Im not going to incubate a double yolker and they dont fit the recipes. They are great for scrambled or fried eggs, but so are regular eggs. If a hen lays more than one egg a day, the shell gland often does not have enough time to produce enough shell material, so you might get a soft shelled or shell-less egg. I sure dont need these either.
It is difficult sorting out fact from fiction on what you read on the internet. Even on the extension sites, you really dont know how reliable that information is, let alone some of the others. And a lot of the research papers are not written in a way that a layman can understand what they are saying.
With all this, I think the bounds of how much protein we feed the chick or chickens are pretty wide. Whether we feed them 15% protein Grower/Developer after Starter for six weeks or 20% combined Starter/Grower for Day 1 until we switch to Layer is not likely to make a significant difference.
Partly it is not what percentage protein we feed that is important but how much actual protein they eat in a day. But more importantly I think it is that they do have a wide tolerance for that protein range without causing any problems.
For example, in that gout article, they say that high protein does not start to cause gout unless it is in the 30% range, though if other factors are present, lower levels can contribute to gout. Or if a hen is out foraging and comes across a nice juicy grub, she is not going to say, I have had my protein requirements for the day so I think Ill pass.
I do think that feeding any nutrients in great excess above requirements is likely to cause problems. I think the target we are aiming for is pretty wide and a shotgun approach works as well as a highly accurate sniper rifle, but you do at least need to aim in the general direction.
Anyway, this is my opinion on the subject. Feel free to ignore or laugh at any of it you wish. It really wont hurt my feelings.
