
Hip scoring should be done before breeding, but the British Veterinary Association/ Kennel Club scheme is a voluntary scheme, so it is up to the breeders to support it if they think it is necessary. Most responsible breeders do support this scheme, and do test their stock before breeding.
This does not mean that the puppies born will be free of hip displaysia. The reason for this is that it is polygenic in nature, which means many factors go towards affecting the hip results. Hip displaysia does not have a known hereditary pattern, although it is hereditary. An example of this, is my own bitch who was scored, her result was 0-0= total score 0, mated to a stud dog whose hip score was 2-2= total score 4, we had 10 pups one of whom scored 11-18= total score 29! (The others that were hip x-rayed, and scored under the BVA/KC scheme, all scored a total of 7 or lower). The parents and grand parents of both the stud dog and the bitch had been scored none scored higher than 4-4= total score of 8. The pups score was a throw back. My breed averages a total score of 9. The current thinking is that 35% to 45% is due to inheritance, other factors are diet, exercise, injury and general health all affect the outcome of the hip score.
I would even so recommend you to buy a pup, from a good breeder who has bred the pups from hip scored parents. The breeder should be aware that if the puppy you buy is from unscored breeding stock, they must point this out to you, before they sell the pup and include it in a sale agreement, otherwise they would be liable under the "sale of goods" act to compensate you if the puppy is affected by hip displaysia.
Some "pet breeders" will not bother to score stock as they think it is unnecessary as their bitch/dog is ok, but technically they are a breeder, if they breed a litter of puppies. They should be concerned about the welfare of any puppy they produce, which includes being responsible and having their stock hip x-rayed prior to breeding.