Inside the Vet's World - Spaying and Neutering – Is there a right time?

Dr. Alexandria Horner DVM, MS, DACT

When to spay and neuter? It's one of the most hotly debated questions in veterinary medicine and one where we are starting to see a massive shift in what was once recommended by most veterinarians. The problem is that this question does not have an overarching answer but needs an individualized approach. In their position statements, the American College of Theriogenology (ACT) and the Society for Theriogenology (SFT) directly support this individualized approach. The position statement states, "The decision to spay or neuter a pet must be made on a case-by-case basis, and this decision should be made between the pet's owner and its veterinarian, taking into consideration the pet's age, breed, sex, health status, intended use, household environment and temperament." This article will highlight the benefits and disadvantages of keeping dogs intact and provide general suggestions to consider when determining when to spay and neuter. 

Most people who own pets, working dogs or breeding dogs, are well aware of the advantages of spaying and neutering, as they are often described by veterinarians, rescue groups, and the media. These advantages include effective population control, decreased aggression, decreased wandering, a decreased risk of being hit by a car and a reduced risk of mammary, testicular and ovarian cancers. A significant benefit to many owners, particularly pet owners, is avoiding "sexual" behaviours or a heat cycle. However, recent research shows that our traditional timing of spaying and neutering before 6 months of age may carry an increased risk of some debilitating joint disorders and certain cancers. Cancers with some link to the timing of spaying and neutering include lymphoma, mast cell tumours, hemangiosarcoma and osteosarcomas -- common cancers which many owners have unfortunately experienced at some point during pet ownership. Further, the joint conditions researched in association with early spaying/neutering include hip dysplasia, cranial cruciate (knee) ligament tear or rupture, and elbow dysplasia. The original research examined the effects of spaying and neutering in three of North America's most popular dog breeds: the Golden Retriever, the Labrador Retriever and the German Shepherd. It found that neutering before a year of age was associated with increased risks of one or multiple joint disorders, 2-4 times more than in their intact counterparts. A paper published by the University of California Davis in 2020 examined multiple research papers to assist veterinarians and pet owners in making informed decisions across 29 different breeds and is publicly available. This paper highlights the implications of when to spay/neuter and suggests how best to proceed. However, it is crucial to consider that these are suggestions and the individual lifestyle of the dog, its owners and potential environmental/social factors that may alter when spaying and neutering is ideal for that particular dog. 

So why does early spaying and neutering cause these increased risks in our canine companions? This question is still being researched, but it comes down to the gonadal (from ovaries or testes) hormone secretions and how they interact with growth and other biological mechanisms. When examining growth, it is believed that spaying/neutering before maturity, before growth plate closure of the long bones has occurred, can result in growth longer than what would be considered normal. This potential abnormal growth can result in abnormal loading and wear on the joint, which, in some dogs, could lead to clinically apparent joint disorders. Another concern is high luteinizing hormone (LH), a reproductive-specific hormone produced by the brain in response to no longer having a negative feedback mechanism from the gonads (ovaries or testes). Essentially, this means that the brain can no longer turn off production and, in turn, produces concentrations up to thirty times higher than what is observed in intact dogs. Preliminary research has shown LH receptors on other tissues within the body other than the gonads. However, their effects on these tissues and their roles in certain cancers and other body tissues are still being examined. This possible relationship may give clues as to why we observe adverse health effects in specific populations of dogs. 

How does one take the above information and the evolving research to make the right decision for the dog in front of us? To answer this question, an individualized approach should be taken by discussing with your veterinarian, researching, and determining if caring for factors that come with an intact animal responsibly is feasible with one's lifestyle. When I approach this question with clients, we look at whether they can manage an intact dog, especially a female, when they cycle to avoid unwanted pregnancy. Some simply cannot and are happy to continue spaying and neutering at 6 months of age. Underlying reproductive abnormality must be considered when deciding on appropriate timing, as some have an increased risk to the dog's overall health and welfare if spayed/neutered too early or too late. For example, female dogs with a hooded vulva, a conformational abnormality, are at an increased risk for urinary tract infections, vulvitis, and vaginitis. Allowing these females to stay intact and experience at least one heat cycle can reduce the risk or limit these conditions from occurring before being spayed. On the contrary, in males, disorders of testicular descent, most commonly seen as cryptorchidism, where one or both testicles do not descend into the scrotum, can carry increased risks of testicular cancers and testicular torsion if not removed by the age of two. These conditions must be discussed with your veterinarian, and if they cannot provide sufficient guidance, referral to a reproductive specialist may provide better insight to help the decision-making process. The next factor to consider is the age of the dog. Female dogs who undergo continued cycling over time without pregnancy are at risk for a potentially life-threatening condition called pyometra, and ninety percent of males over the age of 5 years will develop benign prostatic hyperplasia. Both conditions can be cured and 100% prevented by spaying or neutering. These conditions are not created equal, as medications can manage benign prostatic hyperplasia very effectively in the intact male population. Pyometra, on the other hand, is most commonly managed surgically, and medical treatment is reserved for a certain subset of the female population. 

In summary, when to spay and neuter is not as simple as we once thought it was in the past. Understanding the available information and conversing with your veterinarian or a reproductive specialist can help determine the best option for your dog and your lifestyle.

Footnote:

Parts of this article are based on research from the Society for Theriogenology, as well as studies from Hart et al. (2020) and Kutzler (2020).

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K9Force (2025, February). Inside the Vet's World - Spaying and Neutering – Is there a right time? K9Force April 2025

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