Cockadoodledon't :
The breed and genetics of the birds have changed since your grandfathers day.
What worked then has changed a bit now.
I have a post that I put up yesterday where a Doctor with my local agriculture dept told me that over the years
the traits of genetics have changed and that now the birds get the needed supplement from the laying mash and the scratch mix dilutes their nutritional consumption. She admitted...."""We all used to do it.""""
I have studied on her comments with interest.
Not to be disagreeable, but I don't agree.
Maybe a caged chicken, but it's kind of a generalized statement from a doctor and sounds more like an ad for a feed company and I think many chicken breeders will disagree. Personally, I think it's hard to breed the chicken out of the chicken. They want to eat what they see, even the Cornish Cross seem to know that they are supposed to eat bugs and grass.
I believe this statement might be more true for for hybrid birds like the Cornish Cross, Bronze Breasted Turkeys, fast growing hybrids. Birds of these types need certain nutritional requirements that can be copied in custom blends, but probably are more suited to commercial rations since this is easier for most small flock owners to handle. A bird that grows to 8 pounds in 8 weeks does indeed need a balanced diet to get them there. Even though, a CX will forage, it would rather sit in front of the feeder.
For other types such as the Plymouth Rock, Buckeye, etc..., given enough area, a bird left to free range will find not only what it needs to survive, but they can thrive because you can't put fresh air, green grass, and sunshine in a bag. We supplement with feed, but during the summer months not a lot gets eaten from the feeder.
There are plenty of older sustainable breeding flocks, and even hatchery stock, that hasn't been tampered with much at all other then individual farmers and breeders picking the best traits that they are looking for in their flocks. Trait selection has been going on for thousands of years.
Heres a good article.
http://archaeology.about.com/od/domestications/qt/chicken.htm
The traits I look for in our chickens for breeding are: conformity to the standards, good temperament, ability to forage, best growth, good laying, and healthy.