World Spay Day is commemorated annually on the last Tuesday in February (25 February in 2025).

The commemoration of World Spay Day on the last Tuesday of February, to raise awareness about the importance of spaying and neutering pets, preventing overpopulation and improving animal welfare, presents an opportune moment to challenge and update our thinking regarding when we sterilise our canine companions. 

For years, the standard recommendation has been to spay your dog at six months of age, before their first heat cycle. But is this approach right for all dogs? Recent research suggests that an approach tailored more specifically to your individual dog may better balance the benefits and risks of spaying, especially since reproductive hormones play a key role in canine health beyond reproduction.

Of course, spaying remains beneficial to the overall canine population, decreasing unwanted pregnancies and ultimately helping to lower South Africa’s dog and cat homelessness rate, which the 2024 State of Pet Homelessness Project report lists as a combined 22% for both most popular household pets. Although this percentage is below the global average of 35% homeless cats and dogs in the 20 countries surveyed, sterilisation remains one of the most critical tools for reducing uncontrolled breeding and decreasing pet homelessness. 

Spaying your female dog can also completely prevent pyometra, a potentially fatal infection of the uterus. 

New thinking on timing of dog sterilisation

In relation to your dog, it is not the spaying itself that is of concern, but rather the timing of the procedure and the effects that premature removal of hormones can have on the future health of your individual dog. Decisions regarding when to sterilise should therefore be tailored to the dog’s breed, age, health status and lifestyle, in order to minimise these effects.

Early spaying has been linked to a higher risk of joint disorders such as cranial cruciate ligament ruptures, which can cause painful knee instability, and hip dysplasia, a condition in which the hip joint develops abnormally, leading to arthritis and mobility issues. These risks are particularly pronounced in large breeds, for whom delaying the spay procedure and allowing growth plates to close can reduce risks. However, smaller breeds do not seem to face the same orthopaedic issues resulting from early spaying, making earlier sterilisation less of a concern.

Mammary tumours are the most common cancer affecting intact female dogs, and early spaying was historically believed to significantly reduce this risk. However, recent research questions the strength of this association, calling for more unbiased research to be undertaken. Importantly, delayed spaying may increase hormonal protection against other conditions, such as urinary incontinence, and it decreases the risk of urethral sphincter mechanism incompetence and subsequent urine leakage in larger dogs. Spayed females have also been found to be at an increased risk of mast cell tumours, haemangiosarcoma and lymphoma in breeds predisposed to these cancers.

Hormones also influence behaviour, with dogs spayed early showing a higher incidence of issues such as separation anxiety, noise phobia, excitability, and even fear-based aggression. Therefore, owners of already anxious or reactive dogs should take this into special consideration. 

Consult your vet

Alternatives to early sterilisation include hormonal implants or ovary-sparing spay procedures, which offer ways to manage reproduction while preserving some hormone production. However, these alternatives also have their downside. 

Ovary-sparing spays, despite preventing pregnancy, do not stop a female cycling and attracting males, which can still lead to problematic behaviour. And hormonal implants designed to delay puberty have a reported main side effect of triggering heat cycles, during which the dog can still become pregnant. 

Ultimately, sterilisation remains a vital step in controlling the size of our animal populations. The key new consideration for dog owners is the timing of that procedure. Consulting your veterinarian – or local animal welfare organisations offering free or low-cost services – and weighing the pros and cons for your individual dog will help ensure your pet’s overall health and happiness.

   Dr Liana Coetzee and Roxy, one of Dr Coetzee's childhood dogs.

Disclaimer: The opinions expressed in the article are solely those of the author and do not necessarily reflect the views of the University of Pretoria.