How Young Is Too Young? New Research Shifts Thinking on When to Spay or Neuter

Mar 3

*Kyiv in repose. photo: Ken Gorczyca, DVM*

Recently, a friend asked me when would be the best time to neuter his male German Shepherd puppy, Kyiv. Approaching one year of age, Kyiv is an adolescent, and his bones, muscles, and brain are still growing. German Shepherd dogs can continue growth spurts through their second birthday, and my friend was concerned that neutering his dog too early could lead to medical and behavior issues.

His last dog, Augie, was a Rottweiler/Australian Shepherd mix who had expensive knee issues that required surgeries, and he did not want his new dog to suffer unnecessarily from any health problems that might possibly be related to early neutering. His internet searches on this topic had turned up a growing paradigm shift among veterinarians and researchers about the best time to neuter and spay certain dogs.

Back when I was in veterinary school, the standard recommendation was to neuter or spay all dogs and cats at six months of age. This was our mantra. Later on, shelter medicine shortened the age for these surgeries to 2-4 months so that puppies could be adopted already neutered or spayed (studies had found that when spay/neuter vouchers were offered, only 40% returned to have the procedure, hence the preference making sure the procedures were done pre-adoption). In California today, it is the law that all dogs and cats must be neutered or spayed before adoption from shelters.

Now, however, there is growing research indicating that for some dogs - a minority of breeds, to be clear - it’s best to wait to neuter or spay them until they are fully grown. For large breed dogs, such as Kyiv, this can be as late as two years of age. Most small breed dogs do not seem to present the same issues or concerns related to the timing of spaying or neutering.

It’s important to note that the same priorities may not apply to population health versus individual health, and that there is no hard and fast rule for all dogs. Some studies have shown that depriving dogs of testosterone and estrogens while they are still growing appears to lead to medical issues later in life in some dogs. Healthy bones, for example, need adequate hormones to complete their normal growth. Newer research shows that, for many large breed dogs, early spaying or neutering may lead to knee and hip problems and perhaps affect brain growth itself. Additionally, it appears there may be an increase in some cancers later in life, including hemangiosarcoma, lymphomas, and mast cell tumors.

These findings notwithstanding, veterinary science will need many more studies to determine the whole story, and the balance remains far from clear. In vet school, we were taught that spaying females before their second estrus decreased breast cancer and prevented pyometra, a dangerous infection of the uterus. Male dogs were supposed to be less aggressive and have decreased testicular cancers when neutered early. This is still largely true, but are these declines enough to offset the increase in joint problems and old age cancers? There is limited evidence that neutering males actually decreases aggression and some that it may increase anxieties and fear. But neutering and spaying our dogs also seems to increase their longevity. Aren’t dogs less likely to roam if neutered and spayed? In short, we are at a paradigm shift that remains confusing for all of us who love our canine companions.

Let’s take a closer look at the recent data from friends and colleagues Dr. Ben Hart and Dr. Lynette Hart at UC Davis. Dr. Ben Hart led and published the first study on Golden Retriever dogs in 2013, in which his team found that there were significant increases in cancers, behavior issues, and knee, hip, and elbow problems for Goldens who had undergone early neutering. Both doctors laughingly reported they’d had metaphorical tomatoes thrown at them when they first presented these findings at veterinary conferences, yet today there are multiple studies that confirm them. However, the Harts’ study was also careful to note that, in most cases, caregivers can choose the age for spaying or neutering without increased risk of joint disorders or cancers. (Read the Harts’ paper that highlights the best time to neuter and spay dog breeds affected by early neutering here.

Of course, when considering the broader population of canines, early neutering and spaying can be a key tool to decreasing overpopulation, saving countless dogs from lives of pain and abandonment. Yet, even here there is some controversy. Historical data seems to indicate that the stray population was already decreasing before the 1970s when the spay/neuter mantra came into vogue.

In any case, many in the veterinary profession are now urging that the decision about when to neuter or spay be made on a case-by-case basis. In general, it appears that certain large breed dogs should be allowed to grow fully to minimize potential health issues, but with few exceptions, these issues do not affect smaller breed dogs. If possible, pet owners should always have this discussion with their own veterinarians. Perhaps vasectomies will replace traditional neutering in large dogs…who knows?

Given this newer research and the breed and gender of the individual dog in question, I recommended that my friend wait to neuter Kyiv until he is fully grown at two years of age, when he can also have his umbilical hernia and dew claws removed at the same time. Of course, my friend will have to exercise total responsibility for Kyiv in the meantime - no running free around female dogs, no escaping from the yard, etc.

While my recommendation calmed my friend’s anxieties in the face of confusing information, researchers and veterinarians still have much to learn about this issue. As the paradigm continues to shift, I suggest we all keep open minds about the timing of spaying and neutering and what responsible dog ownership means.

How Young Is Too Young? New Research Shifts Thinking on When to Spay or Neuter

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