What Age Should You Spay Your Dog?

7 min read

By Jessica Vogelsang, DVM

New puppy visits have to be one of my favorite appointments in veterinary medicine. Adorable puppies, excited owners, so many opportunities to lay the groundwork for a long and happy life together. We cover lots of topics: vaccinations, deworming schedules, training, nutrition. During the first visit, one of the most common questions I get with puppies is, “When should my pet be spayed or neutered?”

For a very long time, veterinary medicine offered a fairly standard response: Six months. But why is that? Is it truly in every pet’s best interests to be desexed, and if so, why this particular age? Let’s unpack this very important topic so that you understand the factors we consider when we give you our recommendation for spays and neuters.

Understand Exactly What a Spay or Neuter Entails

A spay, known in veterinary parlance as ovariohysterectomy, is the surgical removal of both the ovaries and the uterus in female dogs. While ovariectomies (removal of the ovaries, leaving the uterus) are becoming more common in other parts of the world, the complete ovariohysterectomy is still the main procedure taught and performed in the United States. In the dog, the ovaries are up near the kidneys, and the y-shaped uterus extends from both ovaries down to the cervix. An ovariohysterectomy is a major abdominal surgery that carries with it, like all surgeries, risk and benefit.

A neuter procedure, or castration, removes the testicles from a male dog. Unless the dog has a retained testicle (a condition known as cryptorchidism), a neuter procedure does not enter the abdominal cavity. While still a major surgery, it is not as complex as a spay in a healthy, normal male dog.

The Size of the Pet Matters

A main reason veterinarians recommend a spay at six months as opposed to six weeks is concern for anesthesia. Very small pets can be more of a challenge in terms of temperature regulation and anesthetic safety, though with today’s advanced protocols, we can very safely and successfully anesthetize even tiny pediatric patients. In a shelter environment, where highly trained and experienced staff perform thousands of pediatric spays and neuters a year, it is not uncommon to perform these procedures in pets closer to two-three months of age.

On the other hand, very large dogs are also more complicated to spay. Not only is the abdominal cavity larger and deeper, the blood supply is more robust and the fat in the abdominal cavity more difficult to maneuver around. Make no mistake, I would much rather spay a six-month-old dog of any breed than a five-year-old, 100-pound Rottie. As the difficulty increases, so does the risk of complication. With male dogs, the procedure does carry increased risk of complication as the pet grows but not to the same extent as a spay. Regardless, veterinarians perform so many of these procedures that we consider them fairly routine, even in large dogs, and the overall complication rate is still very low. Unless a pet has another underlying health issue, size should not be a reason to avoid the procedure.

Removing Hormones can be of Benefit

Another reason veterinarians settle on the six-month recommendation is that if a pet is not going to be bred, spaying a female dog before her first heat cycle has a significant benefit in terms of reducing the risk of mammary cancer. While pets spayed before their first heat cycle have a 0.5 percent incidence of mammary cancer, that number torpedoes to 26 percent for pets spayed after their second heat cycle, with an overall incidence seven times higher for intact females than for spayed ones. Pyometra, a life-threatening infection of the uterus, is also very common in intact female dogs, and up to a quarter of intact dogs will develop it by ten years of age, according to one study. And obviously, a pet with no ovaries, testicles, or uterus cannot develop cancers or infections of those organs.

Testosterone has a great many effects on the dog that are decreased or eliminated when he is neutered. Behaviorally, neutered dogs are less aggressive, less likely to roam and be injured or hit by cars in their never-ending search for a mate and exhibit less of that frustrating humping behavior. Some boarding and daycare facilities do not accept intact pets, which can be a significant obstacle if you usually partake of these services.

Removing Hormones can be of Risk

Recent studies have linked early spay and neuter to a bevy of health risks: increased incidence of cranial cruciate ligament disease, osteosarcoma, hemangiosarcoma, or lymphomas in dogs that were spayed or neutered before sexual maturity. While these studies have received a great deal of attention, it’s also important to note that they are retrospectivethey are looking back on medical records after the factwhich means the data is much more subjective and not necessarily definitive. While it isn’t unreasonable to make note of these associations and continue to study them, the scientific community is far from consensus on whether or not early spay and neuter causes these health problems, or is simply associated with them without being the cause.

There are two medical conditions that are generally accepted as being associated with spay: urinary incontinence and obesity. No one is sure why obesity is seen more in spayed females, as no studies have shown a change in metabolism after the procedure. Both conditions are treatable: incontinence with medications and obesity with diet and exercise.


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