It really depends on the rooster. Most people will tell you 10 or more pullets/hens per cockerel/rooster. The Cochins would be less rough on the girls than the RIR because they are slower than the RIR, so one Cochin would probably be fine with your 7 girls.The RIR has been mating for a few weeks now. In the beginning we didnt know what was going on and one time we thought he was killing one of the buff orpingtons. So we intervened and she had blood on her face and comb and she looked like she had a black eye. And whenever he went near them they would scream and try to get away. But over the past few weeks it's been getting better. Now I see them lowering down when he comes over. And it's over just as fast as it started with no issues. But that's not every time yet! Just this past Saturday we got our first egg from one of the leghorns. She is the only one laying as of today. And yesterday was the first time i saw one of the white Cochins crow and then mate and one more time this morning. Should the RIR only be mating with hens that lay? And could one rooster over mate 7 hens?