Module 8: The Case of the Spay-Neuter Skeptic

Spay-Neuter Controversies

While the benefits of spay-neuter are well-documented, it is not without controversy. Disagreement persists on a number of issues: the age of the animal when sterilized, long-term health impacts, the quality of the procedure performed by HQHVSN clinics, and competition between HQHVSN clinics and private practitioners. As a shelter veterinarian, it is important to understand these issues, to be open to newly emerging information, and to communicate professionally with colleagues and policy makers.

Concern About Age: Pediatric Spay-Neuter

Decades ago, veterinary students were taught that the optimal age for spay-neuter was at least 6 months of age. Some even advocated that females should be allowed to experience at least estrous cycle or even a pregnancy before sterilization. Certainly, delaying surgery to this extent virtually assured that unplanned and unwanted pregnancies would occur, ultimately perpetuating shelter euthanasia.

Prior to widespread acceptance of pediatric spay-neuter, shelters commonly adopted out unaltered puppies and kittens with a contract for the adopter to have the pet sterilized by a certain age. With inconsistent compliance, this proved to be an ineffective means of population control.

The development of anesthesia and surgical techniques tailored to pediatric patients in the 1980s led to the recognition that pediatric surgeries are easier to perform than surgeries on adult animals and cause less discomfort for the patients. Anesthesia and surgery times are shorter, perioperative complications are lower, and rates of recovery and healing are faster.

Long-term Health Impacts of Spay-Neuter: The Cat

In 2016 the Veterinary Task Force on Feline Sterilization met to review existing research and to develop recommendations for the optimal age to spay-neuter cats. After reviewing the scientific literature, they released the following position statement:


Risks and Benefits of Spay-Neuter in the Cat: What the Data Tells Us

Veterinary Task Force on Feline Sterilization Recommendations for Age of Spay and Neuter Surgery

Current recommendations for the age to sterilize (spay/neuter) cats are arbitrary and inconsistent. Adoption of evidence-based guidelines is expected to limit confusion among cat owners, reduce the risk of unwanted litters, and maximize health and welfare benefits. A task force of veterinarians and experts selected from private and corporate veterinary practice, feline specialty practice, shelter practice, organized veterinary medicine, feline health research, behavior, and academia was convened to review the currently available evidence for the ‘optimum age for spaying or neutering cats.’ The Veterinary Task Force on Feline Sterilization task met on January 15, 2016 in Orlando, Florida. The following key findings and proposals emerged from a review of the currently available scientific literature and group discussion:

  • Recommendations for the optimal age to sterilize cats may differ from the age to sterilize dogs. Current scientific evidence documents benefits of spaying kittens before the first estrous cycle, including the following:
    • Decreased risk for mammary carcinoma
    • Elimination of reproductive emergencies such as pyometra and dystocia
    • Avoidance of unintended pregnancies that may occur as early as 4 months of age
    • Potential decrease in behavioral problems linked with cat relinquishment.
  • Current evidence does not support an increased risk for cats of complications or long-term adverse health effects with pediatric (6-14 weeks) or juvenile (>16 weeks) sterilization.
  • More controlled prospective research specifically examining different ages of sterilization in cats is needed. As new information becomes available, the recommended age for sterilization of cats should be revisited.
  • There is potential to increase the number of sterilized cats and reduce the unplanned/unwanted litters of kittens if veterinarians routinely schedule this surgery for client-owned cats at the end of the kitten vaccination series.

Given the known benefits of sterilization and the lack of evidence for harm related to age at which the procedure is performed, the Veterinary Task Force on Feline Sterilization calls for veterinary practitioners and professional associations to recommend sterilization of cats by five months of age. This provides veterinary practitioners with a consistent message that may increase veterinary visits and spay/neuter compliance while reducing the risk of pet relinquishment and unwanted offspring.

Snapshot of news article about Fix by Five


The Journal of the American Veterinary Medical Association reported that the call to sterilize cats before five months of age gained broad acceptance by the veterinary profession. These recommendations resulted in the Feline Fix by Five campaign and are supported by the American Veterinary Medical Association, the American Association of Feline Practitioners, the American Animal Hospital Association, and the Association of Shelter Veterinarians, among others.

Long-term Health Impacts of Spay-Neuter: The Dog

Unfortunately, the optimal age to spay-neuter dogs is not as clear-cut. A growing number of studies have been published on possible adverse health and behavior impacts of canine sterilization on such conditions as neoplasia, orthopedic and joint diseases, urinary incontinence, obesity, and other conditions, often with conflicting results. This places veterinarians in the difficult position of sifting through the data to make the right recommendation for each pet. One size does not fit all.

Fortunately, in June of 2017, this article was published, to help guide our decision-making as veterinarians: Determining optimal age for gonadectomy in the dog: a critical review of the literature to guide decision making.  There is also a webinar by Dr. Philip Bushby, The Optimal Time for Spay/Neuter: An Analysis of Critical Spay/Neuter Literature.


Risks and Benefits of Spay-Neuter in the Dog: What the Data Tells Us

Some key points from these resources are as follows:

  • Many current studies are weakened by the reliance on retrospective records involving a few select cancer-prone dog breeds from academic referral centers that may not represent the general dog population.
  • Prospective controlled studies are preferred over retrospective, as one is less likely to be missing data points or having to rely upon memory. Retrospective studies cannot control for confounding variables such as the effect of genetics, environment, diet, frequency and quality of medical care, and lifestyle.
  • Multiple studies have shown that sterilized animals have increased life-spans. It has also been demonstrated that certain health concerns, such as cancer, increase with age. Therefore, one might expect an increased prevalence of the condition being studied simply because the sterilized animal lived longer than its intact control.
  • Even if a condition is seen twice as often in a sterilized animal, if the incidence is rare, it will still be rare when doubled. Look at the impact in terms of the frequency of occurrence and the seriousness of the condition.
  • The high risk of mammary tumors and life-threatening pyometra in intact female dogs provides a strong argument for spaying female dogs prior to their first heat.
  • Small dogs should be sterilized prior to five months of age as there is no evidence of orthopedic issues in small dogs.
  • There is more concern about orthopedic conditions developing in large-breed dogs, especially if sterilized prior to maturity. Objective risk-benefit data is scarce, and this is an open topic of active research. While shelters often have blanket policies to sterilize all animals prior to adoption, private practitioners have an opportunity to tailor spay-neuter timing to the needs of individual animal


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