Being, a dog breeder, we always tell our new adoptive families to "NOT", fix the boys, until "The Goods" drop and are visible, on the puppy. This varies with breed and age of course.
We mention this "drop factor', because one of our families took their new pup into their vet, for a check up. The vet talked them into having the puppy neutered, while there, and he was only 11 weeks old, no goods showing yet.
Since the good weren't, showing, the vet went into the body cavity, after them. She nicked the inside of the left thigh tendon in her ignorant quest to get an extra few bucks and now, these folks have a $800.00 dog that will limp all its life and cannot run more than a feeble "trot'.
Also, don't expect a real sudden change in behavior, when your male's been fixed. When the testicles are removed, all of that "reserve testosterone" HAS to go "somewhere" and it stays in the male's system for up to 2-3 weeks, after neutering.
One, other, thing then I promise to shut up............... make SURE, that your vet KNOWS what they're dealing with!! Just because someone has a Vet school plaque on their waiting room wall, does NOT mean that they're well versed in ALL breeds and types of dogs!
Or, for that matter, even that good with ANY breed of canine.
The one that ruined the puppy's leg, was an admitted "Cat Vet" primarily. Others, are, "large breed vets", "smaller breeds specialists", etc. Of course, like the 3 vets we use, for our kennels, there are vets that; "can do it all and do it all, very well". Just check them out, a little bit, before going! And, YES...... that IS "a load", about "waiting and breeding them, once, before having then fixed"!
In fact, with FEMALE dogs, if they are bred only one time, then NOT fixed and yet, are not ever bred again, they run an 85% risk of contracting cancer, within the next 3 years, following that once only, breeding.
Sorry, for the long rant/post!! "Dogs Rule" as the ad campaign touts and they really do, relay solely on we humans, for their health and well being.