Neutering 101: What the Discerning Pet Owner Needs to Know

Dr Patty Khuly

Neuter Surgery

According to a variety of definitions, the verb “to neuter” means to change something from a masculine or feminine to a form that can’t be classified as either. But in the land of all things pets, the word “neuter” means something far more specific.

“Neutering” refers to the sterilization of a male domesticated household pet, typically (but not exclusively) via surgical castration. It’s also the term for the procedure itself, referred to casually in the veterinary world as “a neuter.” Male dogs and cats are considered “neutered” when they’ve been sterilized. By contrast, females of these species are said to have been “spayed.”

This may not be news to you, but I go through the motions of explaining the common verbiage because I’ve noticed that plenty of pet owners get tripped up on the terms. In reality, however, neutering is fairly straightforward procedure with only a couple different variations. So simple, in fact, that the way I see it the only tricky part is trying to figure out who gets neutered… and when.

The fundamental goal of neutering a dog or cat is the same: sterilization. The idea is that they are rendered incapable of reproducing. This can be achieved in a variety of ways:

#1 Surgical Castration

In most cases canine and feline sterilization happens in males via surgical removal of the testicles (also referred to commonly as castration or medically as gonadectomy). With the testicles removed, these dogs and cats become incapable of producing a) the sperm needed to carry the male’s genetic material and b) the male sex hormones required to undertake the mating process. It’s a double whammy that leaves zero possibility of any “oops” mating.

While it sounds barbaric, the modern-day version of this procedure is actually quite gentle. The pet is completely anesthetized, his scrotum and nearby skin are cleaned and prepared, an incision is made either in front of the scrotum or at the apex of the scrotum, the testicles are individually exteriorized and their blood vessels and reproductive tubes surgically sliced. Depending on where the incision was made, stitches may or may not be required. A pain reliever is almost always in order.

Pet owners often ask whether a pet’s personality will change afterwards, to which I always emphatically reply, “Absolutely not!” Though pets may tend to behave differently when it comes to male-specific behaviors (humping, roaming, urine marking, and a more sensitive aggression trigger, especially around other dogs) these behaviors in no way constitute personality traits. (It bears noting that some dogs’ behavior does not change in the slightest.)

Though it can be elected at any time in a pet’s life, the procedure is most often undertaken either in preadolescence or right around puberty (at about six months of age).

#2 Chemical Castration for Dogs

While undertaken in other countries, especially throughout the developing world, so-called chemical castration never made it big in the US and is only rarely employed here. The procedure involves injecting a zinc-containing chemical solution into the heart of each testicle, thereby killing a significant percentage of its sex hormone- and sperm-producing cellular infrastructure (about 40%).

Though not considered painful, in the US the patients are heavily sedated for stillness’s sake (it helps ensure accurate administration of the drug). It is a quick procedure with rapid onset of results.

Since it never caught on here, the FDA-approved chemical is no longer readily available for veterinary use. It is, however, a viable alternative that simply never became fashionable, probably for reasons related to the patient’s hormonal behavior afterwards: Do they exhibit any male behaviors? Because results on this varied, and because surgical castration is so overwhelmingly popular, Zeuterin® never made it big.

#3 Vasectomy for Dogs

This procedure is minimally invasive compared to castration. It involves the interruption of only the vas deferens, the tube that carries the sperm itself. The rest of the testicle and its adjacent structures remain intact. Although it’s arguably the simplest of the three procedures (if a little fiddly), vasectomy is wildly unpopular among veterinarians in the US, so much so that many veterinarians actually bristle whenever it’s discussed.

The unpalatability to veterinarians is in part due to a lack of familiarity with the procedure but also because, unlike castration, pets’ natural sex hormone levels are undiminished afterwards. And, though this is beginning to change (a little) for dogs in light of emerging science, US veterinarians still prize sex hormone elimination as much as they do sterilization when it comes to neutering all pets (but especially for cats!).

Cool info, right? I think so. Any pet owner with a male pet should take this basic primer for what it is: a starting point for any questions you may have for your veterinarian. Ask away!

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