The Neutering Debate: When is the Right Time to desex your Dog?
For many years, the standard veterinary advice was clear: desex your dog at six months of age. It was straightforward and aimed to prevent unwanted litters and reduce certain health risks. However, recent research has brought this timeline into question, revealing that the timing of neutering may significantly impact your dog’s health, behaviour, and overall well-being.
Let’s delve into the current science surrounding neutering, the role of hormones, and how to make an informed decision for your pet. It’s important to note that this article is not meant to discourage desexing or cause concern or regret for those who have already made that choice. Instead, the goal is to provide education on the vital role hormones play in the body.
What Happens When We Remove Sex Hormones?
Desexing involves removing the reproductive organs, and with them, hormones like oestrogen and testosterone. These hormones do much more than support reproduction—they play a critical role in growth, mental health, and even immune function.
1. Growth and Orthopedic Health
Sex hormones regulate when growth plates close during development. Desexing dogs, especially large breeds, before maturity can delay growth plate closure, which affects normal biomechanical forces on developing joints. This alteration can predispose dogs to orthopedic injuries such as cruciate ligament tears and hip dysplasia.
For example, a study on Golden Retrievers found that early-neutered dogs were at twice the risk of joint disorders compared to intact dogs (Hart et al., 2014). Allowing your dog to fully mature before neutering can help mitigate these risks, particularly for breeds prone to joint problems. For most breeds this is around 12-18 months.
2. Mental Health and Behaviour
Sex hormones play a crucial role in brain development and behaviour, influencing factors like serotonin regulation, which significantly impacts mood and anxiety levels. Removing these hormones can increase the risk of anxiety, fear-based aggression, or heightened reactivity in some dogs.
Research, including a study by McGreevy et al. (2018), indicates that neutered dogs, particularly those neutered early, may exhibit higher levels of fear and aggression compared to intact dogs. These findings highlight the importance of evaluating a dog’s personality and behavioral tendencies when determining the best timing for surgery.
3. Hormones and the Gut Microbiome
Emerging research highlights the crucial influence of sex hormones, such as oestrogen and testosterone, on maintaining gut microbial diversity, which is essential for digestion, immune function, and gut-brain communication. A recent review by Kraimi et al. (2024) emphasises that gut dysbiosis can result from hormonal changes and play a significant role in disorders of the gut-brain axis. Desexing, which reduces levels of these hormones, may predispose animals to gut dysbiosis by altering microbial composition and diversity.
Supporting gut health in desexed pets through dietary interventions, such as probiotics or nutrient-rich diets, can help mitigate these effects. By promoting microbial diversity, these strategies may play a key role in reducing the risks associated with gut-brain axis imbalances and maintaining overall health. However, further studies are needed to clarify the long-term effects of hormonal reduction on the gut microbiome.
4. Cancer Risks and Hormonal Protection
Another major concern with neutering is the increased risk of certain cancers in dogs. Studies have shown the following:
- Osteosarcoma (bone cancer): Neutered dogs, particularly large breeds, are 2–4 times more likely to develop this aggressive cancer (Torres de la Riva et al., 2013).
- Lymphoma: Golden Retrievers neutered before one year of age have a significantly increased risk of lymphoma (Hart et al., 2014).
- Hemangiosarcoma (cancer of the blood vessels): Spayed females are twice as likely to develop this cancer compared to intact females (Ware & Hopper, 1999).
- Bladder cancer: Neutered dogs have a higher incidence of transitional cell carcinoma, a rare but serious bladder cancer (Mutsaers et al., 2003).
Sex hormones play a critical role in regulating the immune system and maintaining cellular health. These hormones help the body resolve precancerous changes and support normal immune function, acting as a protective barrier against cancer development. When hormones are removed, the immune system's ability to detect and address abnormal cell growth diminishes, increasing the likelihood of cancer. This underscores the need for a personalised approach to desexing decisions, carefully weighing risks and benefits for each dog.
5. Urinary Incontinence in Female Dogs
Urinary incontinence is a common issue in spayed females, affecting 5-20% of dogs depending on factors like breed and timing of spaying. Oestrogen maintains muscle tone in the urinary sphincter, and its removal can lead to urine leakage (Kendall et. al, 2024).
While incontinence can often be managed with medications, delaying spaying may reduce the risk, particularly in larger breeds.
6. Ethical Considerations: Strays and Unwanted Pregnancies
While delaying neutering offers health benefits, it’s crucial to balance these against the risk of unwanted litters, particularly in multi-pet households or areas with stray populations.
Unplanned pregnancies contribute to overpopulation, which leads to overcrowded shelters and abandoned pets. Responsible pet ownership includes measures to prevent breeding, such as secure fencing, supervision, or temporary contraceptives.
What’s the Best Approach?
The right timing for desexing depends on your dog’s breed, size, lifestyle, and health risks. For example:
- Large breeds: Delaying desexing until after full growth (12-24 months) may reduce the risk of joint issues and certain cancers.
- Smaller breeds: These dogs may be less prone to orthopedic issues, so timing can be more flexible.
- Females: Waiting until after the first heat cycle may reduce the risk of urinary incontinence.
Neutering is not a one-size-fits-all solution. While it offers undeniable benefits, such as preventing unwanted litters and reducing the risk of reproductive cancers, it also has long-term health implications that deserve careful consideration.
By understanding your dog’s unique needs, researching the latest evidence, and consulting your veterinarian, you can make an informed decision that prioritises your pet’s health and happiness.
About the Author - Dr. Nicole Rous
Dr. Nicole Rous completed her degree with Honours from the University of Sydney in 2008. She initially worked in the UK before returning to small animal practice in Melbourne, Australia. Dr. Nicole has a keen interest in animal reproduction and has been granted Membership with the Australian and New Zealand College of Veterinary Scientists in this specialty. She is also passionate about complementary therapies such as massage and enjoys discussing ways to enhance pets' overall well-being and quality of life.
In August 2021, Dr. Nicole joined the Mont Albert Veterinary Surgery team as a director and continues to provide exceptional care to her patients. She is dedicated to utilising her knowledge and experience to assist pets in living longer, healthier, and happier lives.
Dr. Nicole's commitment to providing natural and holistic health practices for pets inspired her to establish Shy Tiger, a company that offers natural pet products made from premium ingredients sourced primarily from Australian farms and producers. Her expertise in natural health practices and dedication to providing excellent care to her patients make her a reliable partner for pet owners in Melbourne and beyond.
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