It is probably in a pup's best interest to have them fixed when their growth plates closed. That is something that one can ask their vet to confirm. I think allowing the growth plates to close also allows a pup the chance to lose all the baby teeth that will fall out naturally. That way, when the pup is put under, he/she can have the neuter/spay surgery done, and at the same time have any retained teeth pulled. No need to put the pup under a second time.
