In recent years, “desexing” – spaying and neutering – has become the obvious and natural choice for most pet owners. Apart from population control, it’s often been said that there early neutering is better for the health of the individual animal.

The latest recommendations are that spaying and  neutering should be carried out at an earlier age than has previously been suggested. Some animal rescue groups are spaying animals that are clearly “puppies” and “kittens” for practical and cost reasons.

At the recent WSAVA/.BSAVA/FECAVA congress, the subject of early neutering of pets was the focus of a “debates and controversies” session. The question was asked: “how early is too early?”, but the debate widened to include the question: “should neutering be recommended at all?”

The answer to this question turned out to be complicated: it depends on the individual animal. It just isn’t possible to have a blanket recommendation that is correct for every situation.  Spaying and neutering is not without risk, as with any surgical procedure. Surgery should be only entered into after an informed discussion of the risks and benefits in each individual case.

The benefits are well known:  many now believe that it’s best to spay a bitch before her first season. This eliminates the risk of unwanted pregnancy and the physiological and behavioural changes associated with the reproductive cycle. It also significantly reduces the risk of mammary cancer.

For male dogs, castration eliminates the risk of testicular cancer, the second most prevalent cancer among male dogs. It also reduces the incidence of other non-cancerous conditions of the mature prostate (e.g. benign prostatic hyperplasia, prostatitis/prostatic abscesses, prostatic cysts and paraprostatic cysts). Prostatic hyperplasia starts at 1-2 years of age with 95% of dogs affected by 9 years of age.  Finally, castration dramatically reduces the risk of tumours of the perineum.

In female cats, there are also well known benefits from spaying: feline mammary cancer is the third most common form of neoplasm, though with a lower risk than in female dogs, and 80% of feline mammary tumours are malignant. Entire queens are seven times more likely to develop mammary cancer than those spayed at puberty.

And for tom cats, neutering reduces fighting behaviour by over 80%, significantly reducing cat bite abscesses, as well as reducing the risk of FIV infection. Neutering also significantly reduces male urine marking behaviour.

So what about the risks of neutering? The first adverse effect is well known: spayed and neutered animals are more likely to become obese. In theory, this can be easily prevented by following careful nutritional advice, but we all know that in practice, it isn’t always so easy.

For female dogs, urinary incontinence is the next best known complication. This is more likely to occur in bitches that are spayed at any age compared to bitches that are not spayed. Much research has been carried out on the effect of the timing of spaying on urinary incontinence and there is still debate over whether spaying before the first season marginally increases or marginally decreases the risk of this problem.

In male dogs,  castration is associated with an increased risk of bladder and prostate cancer, but the incidence of these cancers remains very low compared to testicular cancer and other prostatic disease in entire dogs.

More significantly, the WSAVA forum discussed recent evidence that suggests that spaying and neutering before skeletal maturity increases the risk of bone tumours in large and giant breeds of dog. One study in the USA found that the general risk of Rottweilers developing osteosarcoma was one in eight. For neutered Rottweilers, the risk is one in four.  This doubling of risk is something which cannot be ignored, yet it’s still not widely known.

So what advice should vets give to their pet-owning clients?

For vets working in overcrowded animal shelters or in areas where owners are less compliant with the needs of responsible ownership, early neutering is the first choice for nearly every case. Cats are often spayed at less than four months of age, and dogs before six months, and in many animal rescue centres, it’s done even earlier. The surgery seems to be simpler, with animals recovering more rapidly, and subsequent complications from unwanted pregnancies are removed.

For vets working in private practice with well-informed, dedicated pet owners, there’s room for a more detailed debate about the specific needs of the individual animal.

Is it possible to make any overall generalisations? There is a large overpopulation problem for pets in this country, arguably caused by accidental or irresponsible breeding . If vets can generate a belief that neutering is “normal” then we stand a greater chance of reaching those that we do not currently find it easy to reach.

If, on the other hand, vets take a “maybe” stance that openly invites choice, then people are more likely to choose to take the least action and spend the least money. As a result many bitches and dogs will remain entire and many unwanted puppies and kittens will be born.

My conclusion? There are clearly issues about spaying and neutering that deserve discussion with responsible owners who wish to understand the risks of neutering and to weigh them against the benefits. “Desexing” surgery may not be the most appropriate decision in all cases.

But in general, the following rules are most likely to be correct, for most of the time:

Male and female cats should be neutered/spayed  at 4-5 months of age

Male and female dogs should be neutered/spayed at 5-6 months of age