There was a study done not too long ago on age of neutering. It found that the breed and gender of the dog had a lot to do with the best time to neuter. https://www.frontiersin.org/articles/10.3389/fvets.2020.00388/full They didn't study heelers, but it might help you and your vet make a more informed decision. The main thing you can take from the study is that there isn't a single answer for all dogs. If you are being told "neutering at X months is bad" or "you must neuter at X months or your dog will have issues", then you are getting bad information. It is more complex than that.
Testosterone only factors into things with a male dog. And depending on the breed, the testosterone levels vary at different ages, so while one breed male may do best being neutered at 6-12 months because waiting longer increases the risk testosterone related cancers, another breed male may do better being neutered after 12 months for bone development and the risk of testonerone related cancers isn't increased significantly by waiting. For females, the same is true with estrogen. And in some breeds, the age of neutering doesn't have much impact on health at all.
I had Kyrie fixed when she was 5-6 months old. She’s going on six years old now, and I can’t say I’ve noticed any negative impacts to her health at all from that. She’s a super healthy, very nice dog. ♂️
I've read and heard a lot of folks stating that early neutering increases aggression. I had never seen this in person and asked one person for the studies that showed this. They came back with four studies. Three were based on the same questionnaire. None of those three indicated how the questionnaire was handed out (eg, at the vet's to owners who complained of temperament issues, to trainers, to breed clubs, etc). I felt all three of those studies were based more on an owner's perception of their dog's aggression than with any actual data. For example, an owner adopts a puppy from the shelter at 8 weeks and the puppy is neutered before being released. The owners report that the puppy is aggressive. Is that because it's a puppy, because it's a high energy breed, because the owners unwittingly encouraged biting and jumping, etc? The studies didn't really address that. They just determined that because the puppy was neutered young and the owners reported increased aggression that the neutering was the cause of the suspected aggression. The fourth study was a controlled study using several litters of puppies. The study noticed an increase in aggression in the puppies who were neutered early HOWEVER they pointed out that they could not determine the causation. They also pointed out that they only studied the dogs for no more than 6 months after the neuter (the actual time varied depending on what age the dog was neutered) and that the aggression increased right after the surgery but they noticed it seemed to drop off a bit with the dogs neutered at the earliest point, so it may have simply been a reaction to the pain/discomfort after surgery and not a permanent change in behavior. Unfortunately, some experts took that study (and others) and made their own conclusions that "obviously early neutering increases aggression" completely disregarding that study's admonishment to NOT make such conclusions based on the limited data the study provided. This is why it's important to discuss the pros and cons with a trusted vet and not take universal statements from articles as gospel. Factors to consider are: Increased/decreased risks of cancers (see study linked to in my first post) Increased/decreased risks of structural issues (see link) Ability of owner to prevent unwanted breedings Whether the dog will be shown in conformations, etc Contract/adoption agreements including neutering requirements Personal opinion of the owner
