Ask a UW Veterinarian: When to Spay or Neuter?


Sooner or Later to Spay or Neuter?

The question below was featured in the Spring 2020 issue of On Call, the magazine for friends of the UW School of Veterinary Medicine. This expert response comes from Susannah Sample, assistant professor of surgical sciences.

Question: Recently I adopted a young stray pup who wasn’t yet spayed. When I took her to my current veterinarian, I learned that they prefer not to spay/neuter until 6-12 months, so the dog’s body has healthier growth from hormone changes. I’m wondering how much evidence and acceptance there is in the canine community of this theory? –Carol, Madison, Wisconsin

Answer: The scientific support behind the recommendation you received is complicated. The risks of waiting until 6-12 months to undertake gonadectomy (surgical removal of the testes or ovaries) are thought to be low, although increases in surgical difficulty and complications, or other effects such as development of undesirable behaviors, have not been investigated. The evidence for potential benefits requires more discussion.

Over recent decades, routine gonadectomy of dogs and cats pre-adoption has become standard practice, resulting in the prevention of tens of millions of euthanasias each year. Recently, investigation has begun into how or whether undertaking gonadectomy in very young animals increases disease risk; ultimately, the current evidence is relatively weak.

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Relevant studies are almost all retrospective, based off historical records. Retrospective studies are not designed to establish universal alterations in treatment approach, but should instead be used to formulate questions for future work.

Furthermore, studies to date have focused on a limited number of conditions in only a few breeds, and results between studies are at times conflicting. Based on published research, it appears the risk for development of some conditions in some breeds may be increased when gonadectomy occurs at a younger age, but this relationship appears to be disease-, breed-, and gender-specific. For most conditions under investigation, risk due to breed (e.g. genetics) is believed to be most important for disease initiation.

Prospective, forward-looking studies are needed, and results must be interpreted appropriately. For instance, findings from a golden retriever study should not be accepted as applicable to other breeds. Defining the breed-specific genetic basis of these conditions will also be important in understanding the relationship between disease risk, breed, gender, spay or neuter status, and age of spaying or neutering.

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