The two breeds of dogs we are considering, the Jack Russell and the Australian Cattle Dog (Heeler) often have their tails docked. Especially the Jack Russell. If done, you’re suppose to have it done by a Vet (if they are willing) within 5 days after birth to minimize the trauma to the dog. Australia has completely outlawed the practice.
The arguements FOR docking include esthetics and tradition, preventing damage to the tail, especially for working dogs, and removing an easy target during scuffles. Ranchers and professional breeders are the most likely to support docking.
Here are the minutes of a hearing on PREVENTION OF CRUELTY TO ANIMALS AMENDMENT (TAIL DOCKING) BILL with arguements against docking. In it, the following argument is made:
the logical extension of advocating tail docking as a means of
preventing potential injury or harm is like suggesting that we should
remove the tonsils or appendix of all infants in order to avoid
possible tonsillitis or appendicitis in a few adults later in life
It seems the same "extension" could be made for circumcision. I can promise you, it hurts the baby so the fact that tail-docking hurts a puppy isn’t particularly compelling.