Neutering
Male dogs are castrated, and females are spayed, to prevent the possibility of unwanted litters and to avoid potential health risks. If you aren’t able to supervise your dog so that he or she doesn’t mate, maybe neutering is a sensible option. However, there is some debate about the health benefits of neutering.
Male dogs are castrated, and females are spayed, to prevent the possibility of unwanted litters and to avoid potential health risks. If you aren’t able to supervise your dog so that he or she doesn’t mate, maybe neutering is a sensible option. However, there is some debate about the health benefits of neutering.
Long-Term Health Risks and Benefits Associated with Spay/Neuter in Dogs
Laura J Sandborn, April 2007
We are often asked our opinion on whether it is wise to spay or neuter dogs for health reasons. Unfortunately, the answer isn’t clear cut. Here, though, is a summary of a well-researched answer to this dilemma.
This article is an attempt to summarise the long-term health risks and benefits associated in spay/neuter in dogs that can be found in the veterinary medical literature. This article will not discuss the impact of spay/neuter on population control, or the impact of spay/neuter on behaviour.
An objective reading of the veterinary medical literature reveals a complex situation with respect to the long-term health risks and benefits associated with spay/neuter in dogs. The evidence shows that spay/neuter correlates with both positive and adverse health effects in dogs. It also suggests how much we really do not yet understand about this subject.
On balance, it appears that no compelling case can be made for neutering most male dogs, especially immature male dogs, in order to prevent future health problems. The number of health problems associated with neutering may exceed the associated health benefits in most cases.
On the positive side, neutering male dogs:
- Eliminates the small risk (probably <1%) of dying from testicular cancer.
- Reduces the risk of non-cancerous prostate disorders
- Reduces the risk of perianal fistulas
- May possibly reduce the risk of diabetes (data inconclusive)
- If done before maturity, increases the risk of osteosarcoma (bone cancer) by a factor of 3.8; this is a common cancer in medium/large breeds with a poor prognosis.
- Increases the risk of cardiac haemangiosarcoma by a factor of 1.6; this is a common cancer and major cause of death in some breeds.
- Triples the risk of hypothyroidism.
- Increases the risk of geriatric cognitive impairment.
- Triples the risk of obesity, a common health problem in dogs with many associated health problems.
- Quadruples the small risk (<0.6%) of prostate cancer.
- Doubles the small risk (<1%) of urinary tract cancers.
- Increases the risk of orthopaedic disorders.
- Increases the risk of adverse reactions to vaccinations.
For female dogs, the situation is more complex. The number of health benefits associated with spaying may exceed the associated health problems in some (not all) cases. On balance, whether spaying improves to odds of overall good health or degrades them probably depends on the age of the female dog and the relative risk of various diseases in different breeds.
On the positive side, spaying female dogs:
- If done before 2.5 years of age, greatly reduces the risk of mammary tumours, the most common malignant tumours in female dogs.
- Nearly eliminates the risk of pyometra, which otherwise would affect about 23% of intact female dogs; pyometra kills about 1% of intact female dogs.
- Reduces the risk of perianal fistulas.
- Removes the very small risk (<0.5%) from uterine, cervical, and ovarian tumours.
On the negative side, spaying female dogs:
- If done before maturity, increases the risk of osteosarcoma by a factor of 3.1; this is a common cancer in larger breeds with a poor prognosis.
- Increases the risk of splenic haemangiosarcoma by a factor of 2.2 and cardiac haemangiosarcoma by a factor of >5; this is a common cancer and major cause of death in some breeds.
- Triples the risk of hypothyroidism.
- Increases the risk of obesity by a factor of 1.6-2, a common health problem in dogs with many associated health problems.
- Causes urinary tract spay incontinence in 4-20% of female dogs
- Increases the risk of persistent or recurring urinary tract infections by a factor of 3-4.
- Increases the risk of recessed vulva, vaginal dermatitis, and vaginitis, especially for female dogs spayed before puberty.
- Doubles the small risk (<1%) of urinary tract tumours.
- Increases the risk of orthopaedic disorders.
- Increases the risk of adverse reactions to vaccinations.
The traditional spay/neuter age of six months as well as the modern practice of paediatric spay/neuter appear to predispose dogs to health risks that could otherwise be avoided by waiting until the dog is physically mature or (perhaps in the case of many male dogs) foregoing it altogether unless medically necessary.
The balance of long-term health risks and benefits of spay/neuter will vary from one dog to the next. Across-the-board recommendations for all pet dogs do not appear to be supportable from findings in the veterinary medical literature.
Complications from surgery
All surgery incurs some risk of complications, including adverse reactions to anaesthesia, haemorrhage, inflammation, infection, etc. At one veterinary teaching hospital where complications were tracked, the rates of intraoperative, postoperative, and total complications were 6.3%, 14.1% and 20.6% respectively as a result of spaying female dogs. Other studies found a rate of total complications from spaying of 17.7% and 23%. A study of Canadian private veterinary practitioners found complication rates of 22% and 19% for spaying female dogs and neutering male dogs respectively.
Serious complications such as infections, abscesses, rupture of the surgical wound, and chewed out sutures were reported at a 1-4% frequency, with spay and castration surgeries accounting for 90% and 10% of these complications respectively. The death rate due to complications from spay/neuter is low, at around 0.1%.
The full paper has been placed on the CHC discussion group files.
There are lots of opinions about whether castration can change a male dog’s character or help with aggression problems. Maybe it can – but the dog will still have his own personality whether he’s castrated or not.
Understanding the dog and knowing how to help him modify his behaviour is likely to be a more effective way of dealing with aggression than castration. Spaying is a larger operation for a female dog than castration is for a male dog.
Health
Neutering is associated with a reduced risk of testicular cancer in the male, and a reduced risk of pyometra in the female. Other forms of cancer have also been associated with entire dogs. However, studies have also shown that this is not necessarily the case. The jury appears to be out on this.
Weight
Some dogs do appear to gain weight after neutering, while it has no effect on others. Some also develop ‘woolly’ coats.
Timing
Some vets will advocate neutering at an early age.
Some females are neutered before their first season. With the changes in hormones that a female goes through into adulthood, then there doesn't seem to be sufficient research to show that this is a good idea.
Equally with males - even though they don't have a season, they are still maturing until adulthood and to castrate too early does not seem a good idea.
There seems to be too much pressure to neuter young dogs. Although neutering can be a sensible approach, to advocate the wholesale neutering of dogs seems to be a 'society fashion' rather than allowing responsible owners the opportunity to decide for themselves.
This does obviously mean that if we do not neuter, then it is up to us to be responsible and not allow unwanted litters.
Back to:
Ill-Health & Disease
Unwanted Pregnancy
A to Z