If one has a potential stud dog, the sooner one knows whether it is fertile or not the better. It should then be left to mature.

Not so long ago I was looking for a stud dog for one of my bitches. I had seen just the dog starting his career in the show ring, and whose pedigree fitted in with my bitches. At the time he had no important show wins, and had not been used at stud. Luckily the mating worked, and also within a year he was the leading dog in the breed.