Raising keets with chickens causes the guineas to imprint. When they grow up, they lose the ability to understand that chickens are not guineas. Everything can seem fine right up until the first breeding season happens. At that time the guineas do their natural manners which is totally foreign to chickens. Chickens do not speak guinea nor do they understand the physical movements that equate to submission in the guinea language. One of the guinea's favorite pastimes is to attack from behind and pull or break off feathers. This can stress out the chickens very much.
I have raised guinea with chicks and without chicks. Those raised with chicks tormented the chickens unmercifully. Those raised by themselves have nothing to do with the chickens. They keep to themselves and the chickens keep to themselves. I do house my guineas separately but they can free range in the same area at the same time as the chickens and my turkeys do without any of the groups bothering anyone else.
Guineas need much more "personal space" than chickens do. Those that get away with housing chickens and guineas together normally have much more space available per individual bird than most people recommend as the amount of space required for chickens.
I think it works just because I have the space (which is why I specified they need to be able to roam to work), they are basically free range because they hop my fence daily and go do their own thing. The fence is only there to keep coyotes out. When it was just my Guinea Hen Fred and the rest of the flock there were no problems ever, but I think it's because she was a hen. The three males I have are of breeding age and don't bother any of the chickens, again, it's because they basically have free range, and I do have one hen. They were raised with chickens, but don't bother them and go do their own thing during the day. I've been watching my Guinea Hen to make sure they aren't over harassing her, but she seems to be the leader of the group. I have no qualms with eating one or two if they get to big for their britches
