Should we desex animals??

In response to my thoughts on neutering..... I know that there is a lot of contradictory information out there confusing people. There have been many studies on the benefits and risks of desexing animals. A lot of the studies were done on dogs but can be applied to cats also. I will try and summarize what the studies show:

Advantages of spaying females:
If done before 2.5 years of age, greatly reduces the risk of mammary tumours (the most common malignant tumors in female dogs). It also nearly eliminates the risk of pyometra (uterine infection), which otherwise would affect about 23% of intact female dogs - pyometra kills about 1% of intact female dogs. Minor benefits also include the reduced risk of certain other diseases like uterine, cervical, and ovarian tumours (which aren't common).

Disadvantages of spaying females:
If done before 1 year of age, significantly increases the risk of osteosarcoma (bone cancer). Also there is significantly increased risk of certain diseases like cancers of the heart and spleen, hypothyroidism, obesity, urinary "spay incontinence", recurring urinary tract infections, urinary tract tumours (rare anyway). Also if dogs are desexed before puberty, additional risks include underdeveloped vulva, vaginitis, increase the chance of orthopaedic (bone) disorders and adverse reactions to vaccinations.

Advantages of castrating males:
Eliminates the risk of dying from testicular cancer (rare to die from); reduces the risk of non-cancerous prostate disorders, reduces the risk of perianal fistulas (draining tracts from backside), may possibly reduce the risk of diabetes (data inconclusive).

Disadvantages of castrating males:
If done before 1 year of age, significantly increases the risk of bone and heart cancer, hypothyroidism, progressive geriatric cognitive impairment, obesity, prostate cancer (rare), urinary tract cancers (rare). There is also an increased the risk of orthopedic disorders and chance of having an adverse reaction to a vaccination.

There is also the issue of preventing unwanted litters, marking and roaming behaviour, aggression/sexual behaviour, inconvenience of menstruation etc.

The studies showing these findings are by no means exhaustive and cannot be read so simply. Most of the studies were retrospective, in which they simply looked at dogs with a disease and then worked out what percentage were intact and neutered. There are many variable factors involved in diseases and these all need to be considered (such as diet, obesity etc). For example, the study showing the link to bone cancer was done only on rottweilers. Large breed dogs (like rotties and greyhounds) are more prone to bone cancer whereas it is relatively rare in smaller breeds. So to then say to an owner of a Yorkshire terrier or cat, that desexing increases the risk of bone cancer is not really applicable.

I can personally testify that I have seen many cases of mammary tumours and pyometras/serious uterine infections in entire female dogs and also prostatic diseases and testicular tumours in entire male dogs. These diseases are fairly common and preventing them is definitely worthwhile. The incidence of diseases that may be increased with desexing are relatively rare however. Using the example of heart tumours, the actual figures may be an increase from 3 dogs in every 1000 to 4 dogs in every 1000.

At the moment, my feeling is that the benefits of preventing certain common diseases in older animals by desexing outweighs the possible increased risk of certain uncommon diseases. The current research also seems to show that neutered pets tend to live longer than their intact counterparts (by up to 2 years).

I definitely feel that more research should be done in the whole field of desexing, so that we all will be in a better position to judge and make the right choice for all our pets. I practice what I preach - I spayed my own female dog and then fed her appropriately so she didn't gain weight. (Also another benefit of neutering pets is that it keeps me in a job ).