My brother has 5 hens and a rooster. Apparently the rooster was 1 of three and the other two were more vicious, as a result are now resting in the freezer. My sister-in-law's father said you have to have a rooster or the hens will all try and take his place, causing you to have attacking hens. Is it true? Do you need a rooster? If so, what would be the best breed to purchase?