I think the reason the phrase "must be slow growing" is included in the definition is due to the fact that in recent decades, all breeds of chickens in hatcheries were manipulated to reproduce, grow , and /or lay faster, at a younger age, and have bigger and more eggs year round.
This is to forever satisfy the tummies of the ever-growing population, and at the ideal of less or even inferior feeds.
The old breeds, were never manipulated in this manner.
The birds were expected to preform and deal with their own survival in often threatening situations, not at all like we baby our birds today.
Rarely were they fed anything, and if they were it was tablescraps and maybe a few whole grains thrown from an apron.
They had to scracth up their food, bugs and worms would be a much bigger part of their diet than grains of any kind.
Do you think they had less protein than our fed birds of today ?
Maybe not considering that bugs have more protein and the birds of yester years, did not have fish meal or soy additives, so yes, I would say they grew alot slower.
We as humans grew slower and were smaller as well.
Every generation is taller, and bigger as we eliminate disease, and increase the "health" of our feeds.
Illia made the comment a few days ago that got me thinking, who actually has their birds just "living" on the prairie ?
