I have a rooster that has never crowed. He is an Asian hybrid. Mostly shamo. I have had him for almost a year. I bought him at an auction when he was a juvenile bird. I have mainly Asian chickens including Malays and Ayam Cemanis. I like black chickens, so I thought he was pretty cool. I keep most of the chickens in a coop near the house and let them out everyday to forage. I keep only the hens and young in this coop because the roosters are simply too loud. When the roosters start to crow. They get moved away from the house and locked in breeding pens in the bard where the door can be closed and the neighbors are not complaining about them. The black Asian rooster has remained with the hens for the past year. He is full grown and quite tame. sometimes I think he is going to attack me, but he just stands there and looks at me. I have seen him mate with the hens, so I have put some eggs in the incubator to see what his young are like and if the noncrowing part is genetic. The oldest ones have been in there for about a week and a half. The Malay eggs are fertile, but I put a couple of Ayan Cemanis eggs in there as well because I have two of those hens running with him, but sadly they are not fertile. I might put some of the SLW eggs in there as well, but what an ugly cross. But if it is genetic, it would be the first step to producing crowless SLW roosters. I will keep you posted as I learn more.