It depends on whether the roos are related to your hens. If they hatched from home-grown and fertilized eggs, then you should be OK for several generations before swopping for new blood. If they hatched from purchased hatching eggs and your hens were not from the same source, then they should be OK for up to 6 generations.I have 2 roosters that aren't an issue yet as far as the chicks' safety goes, but for breeding purposes.... How long before I need to worry about separating or culling them?