@Ridgerunner - well stated. Why 16%? Is this for nonlayers? Or supplement for free range?
You can get all kind of opinions on what percent protein to feed chickens. There are a lot of different reasons people keep chickens. I think their goals should factor in to how the chickens are fed. If you are raising them for show, you not only need to feed them a diet that gets them big (each breed has a target size and that size is generally fairly big compared to mostly other chickens of that breed) but also a diet that helps keep their feathers soft and shiny. If you are raising them for meat they tend to gain weight more quickly on a high protein diet. If your chickens are for eye candy supplementing their diet with a few Black Oil Sunflower Seeds is probably a good idea, the oil in the sunflower seeds helps keep the feathers looking really nice.
Where I am, the standard Layer is 16%. That is for laying hens if that is all they eat, not meant as a supplement. That's what the commercial layers eat. Most hens will lay quite well on a 16% protein diet. If you provide them with treats, either low protein or high protein, then you can change that. It's not how much protein is in one bite, it is how many grams of protein do they eat all day from all their foods. Even that is not correct, it's more of an average over a few days.
I do think chickens' bodies adjust to their normal diet. If they are used to eating a high protein diet it might be a good idea to feed them a bit more protein than otherwise. If yours free range or forage for a lot of their food you've surrendered control of how much protein they will eat anyway. Lots of moving parts to this.
Why I suggest a 16% protein regimen for those Rangers intended to be kept as a breeding flock is to not grow them tremendously large. Don't get them so big they will injure a leg hopping down from a roost or even just a low perch during the day. Try to reduce the chances they will have breeding problems or health problems because of size.
The more protein they eat the larger the eggs will be. The hens should lay hatchable eggs on a 16% protein diet. They do not have to be huge to hatch.
For the vast majority of our laying flocks I don't think it matters if they eat a 16% or 20% protein feed, either as a standalone diet or with treats as long as the treats don't constitute a large part of the diet. If the chickens can forage for a lot they'll manage that without me trying to micromanage them. But this is a specialty case, trying to get breeders out of chickens meant to convert feed into meat quickly. I think a lower percent protein will be beneficial.
