tail docking

We just had a litter of 7 puppies, 4 male and 3 female. The males were born with NBT trait, natural bob-tails where as the females were born with the traditional long tail. The parents are a European female and an American male. Anyone have more information on the NBT trait? Thanks!

Hi, I know a breeder (former breeder) who was convinced of docking tails via rubber band, the guy brought his tools over and did it on his own puppy and then the "former breeder" allowed him to do it on 5 other dogs. 2 of the tails hadn't fallen off yet, well the people who took two the puppies...