For a few years now, experts have agreed that it is no longer possible to recommend blanket routine neutering of dogs. The days when all it took was a quick call to book a spay or castration because Molly or Spot were now 5-6 months old are definitely over. Owners considering the procedure must be informed of the risks and understand that the dog’s health will in some cases be harmed as a direct result of neutering. To quote a recent study: ‘It has become clear that canine gonads (sexual organs i.e., ovaries and testicles) are not merely reproductive organs, but are critical to endocrine, musculoskeletal, behavioural and anti-neoplastic health.’
Cultural differences play a big role when new dog owners decide whether to have their dog neutered or to leave him or her intact. In some parts of the world neutering of healthy dogs is considered unethical. In Norway routine neutering is actually illegal meaning that around 99% of all dogs in Norway are left intact. At the same time, there are countries where neutering has historically been strongly encouraged and perhaps even regarded as a prerequisite for responsible dog ownership.
Until quite recently many vets certainly considered routine neutering a fairly benign procedure. The most serious side effect was believed to be the risk of urinary incontinence (‘spay incontinence’) in bitches. Then, in 2013, a bombshell was dropped in the form of a major study from the UC Davis School of Veterinary Medicine. The study revealed what no one had previously suspected, that neutered dogs of both sexes have a much greater risk of developing joint disease as well as several different types of cancer compared to intact dogs. In the frenzy of studies that have followed, increased risks of allergies, autoimmune disorders and thyroid disease have been added to the list of side effects and though research is ongoing, it is certainly safe to say that this startling new evidence should make anyone think twice before neutering.
For now, here’s what we know.
Male dogs
Health benefits of castration
- A castrated dog will have a reduced risk of benign prostate hyperplasia in old age and, of course, no risk of testicular cancer. There are, however, no overriding health-based arguments for routine castration.
Health ill effects of castration
- Increased risk of joint disease (cruciate ligament disease, hip dysplasia and elbow dysplasia).
- Increased risk of several types of cancer (lymphoma, hemangiosarcoma, osteosarcoma, mast cell tumours).
- Increased risk of a range of immune-mediated diseases, such as allergies and auto-immune disease
In conclusion, it is already quite clear that routine neutering is not in the interest of a male dog’s health.
Female dogs
Health benefits of spaying
- No risk of pyometra (womb infections).
- Reduced risk of mammary tumours (breast cancer).
Health ill effects of spaying
- Risk of urinary incontinence and increased risk of cystitis.
- Increased risk of joint disease (cruciate ligament disease, hip dysplasia and elbow dysplasia).
- Increased risk of several types of cancer (lymphoma, hemangiosarcoma, osteosarcoma, mast cell tumours).
- Increased risk of a range of immune-mediated diseases, such as allergies and auto-immune disease.
In conclusion
In conclusion, there are some health benefits to neutering female dogs as well as some serious increased risks. This makes the decision less clear-cut than is the case for male dogs. For this reason it is important that vet and carer together weigh up the pros and cons in each case before making a decision, taking account of her family history, breed, lifestyle etc. If she is not roaming free but rather living in close proximity to responsible and informed owners who know to take her to a vet if she becomes unwell and who can look out for a vaginal discharge and lumps in her mammary glands, keeping her intact is probably the safest option. Mammary cancer and pyometra are both common diseases that are treatable and only rarely become fatal if caught in time. In contrast, several of the cancer types that are seen primarily in neutered bitches are harder to detect and will be fatal once the diagnosis is made. Certainly for bitches of breeds with a higher than average cancer risk (Burmese Mountain dogs, Golden Retrievers, Flat-coated Retrievers, Rottweilers etc) neutering may result in a significantly increased risk that she simply cannot afford.
Please note that the above information relates to routine neutering of healthy dogs only. If your dog has an illness (such as testicular cancer or a womb infection) this may tip the scale in favour of neutering. In the case of healthy dogs, however, it is now clear that neutering will have an overall detrimental effect on the health of male dogs. It also looks like bitches are healthier when left intact, though this requires the carers to look out for signs of mammary tumours and pyometra, both diseases that are quite common but, when caught early, rarely fatal. Some owners choose the procedure known as OSS (ovary sparing spay) which leaves the bitch hormonally intact but removes the risk of pyometra by removing the uterus.
The main point so far is that everything we thought we knew about neutering as recently as five years ago has since gone out the window. It is for instance not yet clear what role the age of neutering plays or to what extent breed differences affect the risks. What is clear is that neutering is not as safe as previously believed.
Out Now
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Article by Dr Lise Hansen.
