What is the best age to desex my dog?

There is a growing body of evidence suggesting that early age desexing has more risk than benefits for our beloved dogs. Traditionally desexing dogs and cats at around the age of 6 months has been considered responsible pet ownership. However recent research suggests that its impact on reducing shelter populations may be less significant than previously thought. Owner surveys reveal that a significant percentage would reconsider desexing their dogs if given the choice again, underscoring the importance of informed decision-making and client education.¹

When weighing the pros and cons of desexing, it’s crucial to consider disease prevalence, which varies by breed and region. Desexing can reduce the risk of reproductive diseases such as mammary tumours, testicular tumors, uterine infections and prostate issues. However, it may also be associated with an increased risk of other health issues, such as orthopedic diseases and other cancers.² It’s important to talk to your veterinarians and assess each dog individually and consider factors like breed predispositions.

Several diseases and health risks have been linked to desexing;

• Orthopedic Diseases: Some studies suggest that desexing, particularly at a young age or before skeletal maturity, may increase the risk of orthopedic diseases such as cruciate ligament disease, hip dysplasia, and elbow dysplasia, especially in certain breeds.³
• Cancers: While desexing can reduce the risk of reproductive-related cancers such as mammary tumors and testicular tumors, it has been associated with an increased risk of other cancers, including osteosarcoma, hemangiosarcoma, lymphosarcoma, mast cell tumours and transitional cell carcinoma. The relationship between desexing and cancer risk can vary by breed, sex, and age at desexing.
• Urinary Incontinence: Desexing, particularly in females, has been linked to an increased risk of urinary incontinence, a condition characterized by the involuntary leakage of urine. Larger breeds and those desexed at a younger age may be at higher risk.
• Obesity: Desexing can alter metabolism and hormone levels, leading to changes in appetite and energy expenditure. As a result, desexed animals may be more prone to weight gain and obesity, which can increase the risk of various health problems such as diabetes, joint issues, and cardiovascular disease.
• Behavioral Changes: While desexing can reduce certain undesirable behaviors, such as aggression and roaming, it may also lead to other behavioral changes, including increased fearfulness, anxiety, or reactivity in some individuals.
• Autoimmune Diseases: Some research suggests that desexing may be associated with an increased risk of autoimmune diseases, such as hypothyroidism, immune-mediated hemolytic anemia, and immune-mediated thrombocytopenia.
• Endocrine disorders; research shows that desexing may be increasing the risk of endocrine diseases such including hypothyroidism and Cushing’s disease, atypical Cushing’s disease (hyperadrenocorticism).
• Evidence suggests there is a higher incidence of adverse vaccine reactions in desexed dogs.
• Studies show desexed dogs have an Increase risk of infections diseases
• Over all – the evidence is pointing to a shortened lifespan for early desexed dogs.

Recent literature suggests that desexing dogs at older ages, typically beyond 12-18 months, may have fewer adverse effects on developmental and degenerative diseases. However, the decision should be tailored to each dog’s specific circumstances and health risks including the ability for owners to appropriately restrain their animals and prevent unwanted matings and puppies.

The procedure options for desexing have traditionally only including traditional methods like ovariohysterectomy and castration. However newer techniques are becoming more available such as ovary-sparing hysterectomy and vasectomies. These offer the ability to retain the natural hormones while still preventing reproduction. Suprelorin implants are available as a chemical castration in male dogs for 6 or 12 months.⁴ Off label use of suprelorin implants in female desexed dogs is also proving to be helpful in replacing some of the hormonal loss.

Behavioral considerations also play a role in the desexing decision. While desexing may reduce certain undesirable behaviors like urine marking and aggression, its impact on behavior is nuanced and varies among individuals. Research suggests conflicting results regarding the effects of desexing on behavior, highlighting the need for personalized recommendations and ongoing monitoring.

Ultimately, the decision to desex a dog should be based on a thorough evaluation of individual health risks, breed predispositions, owner circumstances, and the latest scientific evidence. Assessing the risk vs benefits with your veterinarians along with what other options you might have such as ovary-sparing spays and vasectomies will help you through this decision-making process and ensure the best possible outcomes for canine health and welfare.

Ultimately if you are going to desex your dog I would recommend (as long as you can adequately restain your pet ) to let females have 1 – 2 heats and wait until male dogs are fully mature (between 12 months and 2 years old depending on the breed).

Cats are a little different. There is no current evidence supporting delaying desexing in female cats and a lot of reasons to desex before their first heat including reducing their risk of mammary cancer by 91%. Thus I recommend that female cats are desexed from 5 – 6 months old.

Studies show that male cats benefit from their hormones allowing their genitals to mature until 7 months old (as opposed to 7 weeks old). Thus I recommend desexing male cats at around 7 – 9 months old ( as long as they are not allowed to roam before this time).

Sources:

1. Dr Abbie Tipler, Mar 7, 2023 ↩︎
2. Vet Education, 2024 ↩︎
3. Virbac, The Suprelorin Webinar series, Dr Xavier Schneider ↩︎
4. Virbac, The Suprelorin webinar series, Dr Michelle Kutzler ↩︎