A long time ago, I safely and successfully castrated all of our bull calves, for many years on a small mixed farm.[I also castrated our boar pigs in that same era] One thing I can remember clearly, was being told by my old man to always make sure that there was the space of a thumb width between the testis and the point where the ~Burdizzo castrator jaws were to close on the cord. I was warned that accidentally nipping of the stone was considered to be very serious matter and could lead to the death of the animal. With all the regulation that is in place today I am not even sure that castration, by the farmer is now permitted. It is a skilled job, I believe and should not be attempted by anyone who has not been shown how to do it properly.