I think it depends partly on flock size and purpose; a flock of only a few birds probably shouldn't be given all the castoffs from a whole restaurant, lol. Personally, I feed my flock of 50 birds as many scraps as are available for them to eat. I'm not going to throw food away when I'm paying 12 bucks a bag for layer pellets! Yes, that means that some days they end up getting as much 'unhealthy' food (stale bread) as they want. Other days it's only some veggie ends, or even nothing at all but layer feed. I love pizza too much to let any be left over, but if it came in as an extra, I most certainly would give it to them. I suspect the nutritionists among us would clutch their pearls if they saw my birds' diet, but they're healthy and hardy and look normal when I butcher them—so I'm not going to quit doing it. Sure, maybe it's not perfect, but they're chickens, for goodness' sake. If they're so delicate and dumb that they can't at least partially manage their nutritional intake by themselves, I sure don't want them in my breeding population. <<shrugs>> And yes, I absolutely have noted that many birds do have the good sense to not simply eat themselves sick on the goodies.
I haven't had chickens for long, only five years, and I sell or butcher most of the layers after 2 yrs so I'm not certain what their lifespan would be if left alone. Out of the birds I started with, one hit nine years of age and was still trucking when I gave her back to her original owner. Out of the birds I started from chicks, the oldest one that I didn't sell is a four year old Silkie. Still in perfect health.
I need to build another coop.
Lol!
