At what age are chickens considered full grown?

[Willow's Meadow]

I heard that once you move 4-5 week old chickens from the brooder to the coop you shouldn't start free ranging until they are full grown and up until then keep them in a run. But how old is full grown?

 

[gritsar]

Depends on the breed. I raise brahmas and they aren't considered full grown until they are two. Now that my flock is two years old I can say for certain that they do indeed keep growing and developing until they are two.
I started taking them outside, with supervision at two and a half weeks old. At around 10 weeks old they discovered that they could fit through the openings in the fence and explore the farm. They've been free ranging ever since.

 

[Kittymomma]

Hi,

I don't move mine in with the big girls and boys until they are around 12 weeks and nearly full size because otherwise the adults pick on them too much. I've done it earlier, but only when I have more youngsters then old-timers. As far as freeranging goes I let mine run around with the rest of the flock at around 10 weeks, they're not full grown, but they're big enough that my cats don't mess with them and I think that's the big thing. I have a broody hen that just hatched out a clutch yesterday and might let them start running with the flock this weekend. If she can protect them from the other chooks and the cats it would be so much nicer then having to integrate them all later, but I'm not sure if it will work.