How old does a rooster have to be in order to be with my hens...also will my silkie rooster fertilize my barred rocks eggs.
I don't think that it's age so much as size. You really want to wait until everyone is about the same size, though if you're referring to a silkie roo being integrated in a LF flock, you may be in for trouble. Due to general fluffiness and fluff-obstructed vision, silkies tend to present "pick on me targets" for other chickens, particularly LF with unobstructed sight. So he might be in for a rough time, and I'm not sure how he'd do fertilizing one of those big fluffy-rumped hens. If I were you, I'd probably wait until your fellow was crowing and "raring to go" and then put him in a decent-sized crate (with food/water) IN the run with the rest of the flock for a good week or so. Then start free-ranging him with them after 3-4 days. Let everyone see everyone else and soften the blow to the pecking order once you loose him on them.