Without going into a deep genetics debate. From my experience,"others may have their own opinion". i would not breed this roo if the leakage is serious as you say. depending on the hen(s) bred with him, they might produce offspring with or without the leakage. Breed him to one hen at a time and see what they produce, cull any offspring that have any sign of the leakage. I would not include that roo in my breeding program again. Breed the original hen to one of her best sons " no leakage at all" and see what happens. Keep on breeding the birds that show no sign of leakage, try to avoid brother/sister matings.