i had zack neutered at just over 7 months, and i'm glad i did. He was changing rapidly at that time and was developing some new behaviors, not a problem really, like Sandy said, he's a cavalier, he was sweet and cooperative, obedient and nonaggressive, but he was getting a bit sexualized
just before i got him neutered i had discovered dog parks (two weeks before), he was ecstatic at dog parks and i was overjoyed to see him having so much fun, most imporantly, the freedom, to know he was safe running around freely, the other owners paid attention to their dogs, and in about 5 or 6 visits between when i discovered the dog park and when i got him neutered, i never saw any dog fights or violence, but i was getting uptight, especially after reading a thread on here about neutering, afraid a female in heat would come to the park, i didn't want zack to get somebody pregnant, and i worried that other male dogs who were much larger might be more of a threat to zack if he was unneutered. I wanted to be relaxed and not worried about Zack running loose with other dogs, that's one reason i decided to do it at that time.
He started lifting his leg for the first time while at the dog park and i was worried about the onset of marking behavior.
I tried to research and find out information about potential health risks of neutering and was not able to find much, so i went ahead and had it done, and i like the noticeable changes in zack as a result, not so much changes but the arresting of tendencies he was beginning to get.
He's very docile and happy. I did not want to see him become increasingly frantic about other dogs, which was starting to happen, lots of shrill arf-ing when he'd see other dogs at a distance, very emotional and, well, frantic. That was the biggest behavioral or emotional reason for my choice to get him neutered, and that frantic intensity gradually died down following the neutering. He still gets excited about other dogs, but now, he listens to me when i 'shhh' him if he arfs, and he calms himself down when i tell him it's ok, 'easy boy, calm down, quiet, it's OK,' and then i don't have to struggle with him or keep my attention on him, he becomes more calm and quiet in public where he used to be much more excitable and not in a happy way, about other dogs and people too.
It's been over a month and a half and so far there's no sign of him slowing down, he's actually been more active, like, up all night doing stuff, not sleeping, not sleepy, interested in stuff, entertaining himself, playing, bringing me a ball to throw, chewing toys. so i haven't yet seen him grow more slothful which is one of the downsides of neutering.
But i am still interested in hearing all sides of the subject and am interested in the reasons any respectable breeder who cares about their puppies would ask puppy buyers to postpone neutering until one year. I ask because i don't know the reasons and am curious about it. i know there are good reasons not to neuter/spay, but i don't know what they are.
The breeder my daughter Lisa got her cavalier Belle from told her to do it right after the first heat, otherwise the risk of breast cancer would be higher.