Neutering – what are the facts?

The Animal Care College – caring for people caring for animals

‘Science is facts; just as houses are made of stone, so is science made of facts; but a pile of stones is not a house, and a collection of facts is not necessarily science’. French mathematician,  Jules Henri

Some disturbing information came my way courtesy of the dog trainer, Stan Rawlinson.  He told me that the RSPCA have a policy of neutering bitches and castrating puppies as young as six weeks old.  I had to read it twice and took the trouble to ring the RSPCA to find out the facts.  This is a policy that has been in place for three years but clearly, and understandably in my view, it has been given very little publicity.

The RSPA issued a statement: “Neutering dogs at six weeks old may sound upsetting to people, but we can reassure them that it is only done in a limited number of cases, for absolutely genuine reasons, and with positive results – offering those animals a chance to be quickly rehomed and given a loving home. Early neutering must be judged against the alternatives.  Our policy is based fully on sound, peer-reviewed science. There are many benefits associated with early neutering. In fact, it can be better for the animals’ welfare – for example the surgery is quicker, there are fewer complications, and the experience is less traumatic when it’s carried out on young dogs. All RSPCA dogs are neutered before they are rehomed, with the exception of a few breeds which some evidence shows are more prone to incontinence after spaying. By carrying out the procedure as early as possible, we reduce the time the animal has to spend in a stressful kennel environment and are able to get them settled into a loving new home more quickly. The RSPCA re-homes thousands of unwanted dogs and puppies every year, and we recommend neutering as a good way to help reduce the problem of unwanted litters. If scientific evidence showed that this policy was wrong, then obviously we would reconsider. But at the moment we are dealing with a very real problem” .. of overpopulation … “with a sympathetic, practical and scientifically-backed policy. The RSPCA generally neuters ‘owned’ dogs at around 14 weeks of age. At the Greater Manchester Animal Hospital, up to 50 stray/abandoned dogs a year are neutered at six weeks of age.’

My immediate reaction to this statement is ‘where is the peer reviewed evidence?  On which such a policy could be based’. I began to do some research.

Firstly I should express my personal view, developed over almost 40 years of breeding dogs and writing about the subject, is that neutering, when necessary, is best carried out once the dog is mature.  I should state to that I am not in favour of neutering unnecessarily.  For both dogs and bitches it is an operation involving invasive surgery and I am against putting animals through unnecessary trauma.  When you consider the fuss which has been made about docking and the removal of dew claws, neither of which are invasive and both of which are very minor procedures, it seems bizarre to me that so many individuals and groups are perfectly happy to recommend neutering for reasons which, I now discover as a result of the research for this article, may not be founded on good science.

Survey of peer reviewed research

            Three years ago in the US Laura Sanborn reviewed the veterinary medical literature in an exhaustive study to unravel the complexities of the subject.  More than fifty peer reviewed papers were examined to assess the health impact of neutering and her conclusions, endorsed by an acknowledged expert, Professor Larry Katz, Chairman of Animals Sciences at Rutgers University in New Jersey are extraordinarily interesting and I believe very important.

It is an extensive treatise and this is just a very brief summary of findings.  I should emphasise that they are based on extensive research by veterinarians and scientists so they are the facts not opinion.  She says in her summary that the literature reveals a complex situation with respect to the long-term health risks and benefits associated with neutering dogs.  She says it is clear that there are both positive and adverse health effects and she also says that there is much that we do not yet understand about the subject (my italics).What is important is that on balance she says, it appears that no compelling case can be made for neutering most male dogs in order to prevent future health problems.  In fact she goes on to say that the number of health problems associated with neutering dogs actually exceeds the health benefits under those circumstances.  On the positive side, neutering male dogs eliminates the very small risk (less than 1%) of dying from testicular cancer, reduces the risk of non-cancerous prostate disorders, reduces the risk of perianal fistulas and may reduce the risk of diabetes although the data is not conclusive.  On the negative side she says that the evidence shows clearly that neutering male dogs before one year of age significantly increases the risk of bone cancer which is very common in medium to large breeds.  It also increases the risk of cardic hemangiosarcoma by a factor of over 12%, triples the risk of hypothyroidiam, quadruples the small risk (about .5%) of prostate cancer, doubles the small risk (less than 1%) of urinary tract cancers, increases the risk of orthopaedic disorders and increases the risk of adverse reactions to vaccinations.

She says that for bitches the situation is more complex.  The number of health benefits associated with this may exceed the associated health problems in some although not all, cases.  Whether spraying improves the 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 the different breeds.  On the positive side, spaying bitches, if done before two and a half years of age greatly reduces the risk of mammary tumours, the most common malignant tumour in female dogs.  It almost eliminates the risk of pyometra  which otherwise would affect about 23% of intact female dogs although she notes that pyometra  only actually kills about 1% of intact female dogs.  (This is a very important and practical distinction for the cost of a spay these days is probably little less than the operation required to deal with a pyometra and the chances of a bitch dying from the condition is actually quite low).  Spaying also reduces the risk of perianal fistulas and  removes the very small risk less than .5%) from uterine, cervical and ovarian tumours.  The bad news is that on the negative side, spaying before one year significantly increases the risk of bone cancer, common in large breeds and which has a poor prognosis. It also more than doubles the risk of splenic hemangiosarcoma  and cardiac hemangiosarcoma by a factor of more than five.  Further problems are that spaying increases the risk of hypothyroidism, doubles the risk of obesity, causes urinary incontinence in up to 20% of bitches, increases the risk of persistent or recurring urinary tract infection by a factor of 3 to 4, increases the risk of recessed vulva, vaginal dermatitis, and virginits especially for female dogs spayed before puberty (my italics), doubles the small risk (less than 1%) of urinary tract tumours, increases the risk of orthopaedic disorders and increases the risk of adverse reaction to vaccinations.

Advice on neutering is exeggerated

She concludes that it is clear that much of the spay/neuter information that is available to the public is unbalanced, contains claims that are exaggerated or unsupported evidence.  She says that rather than helping to educate pet owners, much of it has contributed to common misunderstandings about the health risks and benefits associated of neutering.  What is more, the traditional neutering age of six months as well is the modern practice of paediatric neutering, appears to predispose dogs to health risks that would otherwise be avoided by waiting until the dog is physically mature.  In the case of many male dogs and from a medical perspective, neutering should not be considered an option unless medically necessary.  She concludes: ‘the balance of long-term health risks and benefits of neutering will vary from one dog to the next.  Breed, age and gender are variables that must be taken into consideration in conjunction with non-medical factors for each individual goal.  Across the board recommendations for all dogs do not appear to be supportable from findings in the veterinary medical literature.’

And this is just the start for Ms Sanborn has concentrated entirely on the physical health and well-being of dogs rather than any impact on the dogs’ psychology.  There is a raft of opinion on the subject although I must stress that very little is founded on sound research and I will be discussing the implications of neutering on the mental development of dogs (and the important social/environmental factors next time.

12th August 2011