
In my own breed it would be considered rather rude and wasting of the breeders time to book with several breeders, but we are a numerically small breed. with us you would book with the breeder that you liked, or was the one about to have a litter, and if they happened not to end up with a pup available you would be passed on to the next breeder with pups available, as sometimes one breeder may have all girls and another all boys etc.
I would advise with such a numerically strong breed which will be much more prone to exploitaion by puppy farmers and those breeding only for profit, that you should contact the National and Regional breed clubs for advise. They will normally have a puppy list or list of breeders planning litters, and their members will be required to breed in accordance with the clubs code of ethics, regarding health checks, age and frequency of breeding, and responsibilities to the pups and their new owners.
The secretaries will also more than likely know who the rogue breeders are producing sub standard pups.