It is “common knowledge” that you should spay or neuter your dog to prevent a raft of issues, from saving your male dog from certain death from testicular or prostate cancer, to the almost certain demise of your bitch to mammary tumors or pyometra. Then, of course, there’s the requirement that a dog (especially males) MUST be neutered to eliminate aggression issues (as a total aside, this is likely untrue, as this CO study shows no statistical difference in bites between neutered and non-neutered dogs). Many of us have visited the vets office, and have been asked the not-so-open ended question, “When exactly WILL you want to schedule an appointment to have your dog ‘fixed’?”

It may vary by country or region, but in my part of Canada, people who do not spay or neuter are considered negligent or neglectful, cheap, or somehow oddly unable to remove a dogs “bits” due to some misguided weak-kneed inability to “do the right thing” because it makes them queasy. There may be a bit of slack given to “legitimate breeders”, but not a lot.

The question is rarely asked, however, “is the ‘common knowledge’ actually based on science?”

In 2007 (a number of vet visits ago ) Laura J. Sanborn at Rutgers University did a rather comprehensive review of 50 peer reviewed studies, and the introduction shows how the data is at odds with popular lore:

More than 50 peer-reviewed papers were examined to assess the health impacts of spay / neuter in female and male dogs, respectively. One cannot ignore the findings of increased risk from osteosarcoma, hemangiosarcoma, hypothyroidism, and other less frequently occurring diseases associated with neutering male dogs. It would be irresponsible of the veterinary profession and the pet owning community to fail to weigh the relative costs and benefits of neutering on the animal’s health and well-being. The decision for females may be more complex, further emphasizing the need for individualized veterinary medical decisions, not standard operating procedures for all patients.

I find it interesting that vets either do not seem to have access to this study, or have apparently not heeded it. In fact, I have postulated that there is a coincident relationship between a veterinarians’ desire to get you to spay and neuter and the problem of total lack of revenue that a dog owner poses outside of the typical vaccination visit. That’s a bit “conspiracy theory” like, but it seems plausible. I suspect, however, that it’s really just the case that — with the prevalence of information on the internet that is mired in the old thinking — they are not seeing any demand to reduce the number of operations.

As an example of this here is an ASPCA link showing the top 10 reasons for spay/neuter (my comments are in red below each):

Not convinced yet? Check out our handy—and persuasive—list of the top 10 reasons to spay or neuter your pet!

1. Your female pet will live a longer, healthier life.
Spaying helps prevent uterine infections and breast cancer, which is fatal in about 50 percent of dogs and 90 percent of cats. Spaying your pet before her first heat offers the best protection from these diseases.

Apparently not that clear cut, according to the above study.

2. Neutering provides major health benefits for your male.
Besides preventing unwanted litters, neutering your male companion prevents testicular cancer, if done before six months of age.

Half true, at best: they conveniently fail to point out the potential detriments, which actually seem to outweigh the positives.

3. Your spayed female won’t go into heat.
While cycles can vary, female felines usually go into heat four to five days every three weeks during breeding season. In an effort to advertise for mates, they’ll yowl and urinate more frequently—sometimes all over the house!

True. (Finally ). Though a little bit dramatic, there, no? I guess that was more of a cat related note, tho’.

4. Your male dog won’t want to roam away from home.
An intact male will do just about anything to find a mate! That includes digging his way under the fence and making like Houdini to escape from the house. And once he’s free to roam, he risks injury in traffic and fights with other males.

Orthogonal (not related) really: If you have a large breed, such as a Boerboel, if he roams you are probably being a negligent owner. Whether they roam with or without intact sexual organs is functionally irrelevant to the problem.

5. Your neutered male will be much better behaved.
Neutered cats and dogs focus their attention on their human families. On the other hand, unneutered dogs and cats may mark their territory by spraying strong-smelling urine all over the house. Many aggression problems can be avoided by early neutering.

Um. Look, I’m not neutered, and I do a pretty good job of focusing my attention on my family.

I think this is similar to the above: If you cannot control your dog to stop “marking” you have a training issue, not a medical one (and ask around with people in the dog world who have Boerboels or other large breeds and see how many have dogs that “mark” within the house — after a couple of corrections, anyway. I don’t think they’d get away with that behavior very long. )

6. Spaying or neutering will NOT make your pet fat.
Don’t use that old excuse! Lack of exercise and overfeeding will cause your pet to pack on the extra pounds—not neutering. Your pet will remain fit and trim as long as you continue to provide exercise and monitor food intake.

Fair enough – what they are saying is that ya, drive will drop, so modify food intake. That works.

7. It is highly cost-effective.
The cost of your pet’s spay/neuter surgery is a lot less than the cost of having and caring for a litter. It also beats the cost of treatment when your unneutered tom escapes and gets into fights with the neighborhood stray!

True, assuming you’re negligent enough to let your animals wander, again.

8. Spaying and neutering your pet is good for the community.
Stray animals pose a real problem in many parts of the country. They can prey on wildlife, cause car accidents, damage the local fauna and frighten children. Spaying and neutering packs a powerful punch in reducing the number of animals on the streets.

This is actually a point I sort of see: Basically (and this is a theme to a few of my answers) if you’re not astute enough to keep control of your animals, you may want to either do a spay/neuter, or — better yet — get a fish tank and some goldfish. They are easier to control, and if you can keep them alive for a few years, move up to a gerbil, etc.

9. Your pet doesn’t need to have a litter for your children to learn about the miracle of birth.
Letting your pet produce offspring you have no intention of keeping is not a good lesson for your children—especially when so many unwanted animals end up in shelters. There are tons of books and videos available to teach your children about birth in a more responsible way.

Absolutely true. There are enough dogs and cats out there, we don’t need random breeding just to do a show kids what they can see on YouTube, or at a breeder’s.

10. Spaying and neutering helps fight pet overpopulation.
Every year, millions of cats and dogs of all ages and breeds are euthanized or suffer as strays. These high numbers are the result of unplanned litters that could have been prevented by spaying or neutering.

Absolutely true. Same as above.

I guess my point in the above is that — assuming you’re an owner or prospective owner of a breed as substantial as a Boerboel — the CONTROL of said dog is more important than the medical altering of that dog. The side effects of the procedures are — according to the study — not insignificant, and if you’re doing it mostly because you’re expecting a magic reduction in aggression or because that will make them suddenly a “better dog”, it may not work out as expected. As for health effects, read carefully and evaluate how it applies to you.

From the conclusions of the study:

For female dogs, the situation is more complex. The number of health benefits associated with spaying may  exceed the associated health problems in many (not all) cases. On balance, whether spaying improves the  odds of overall good health or degrades them probably depends on the age of the dog and the relative risk  of various diseases in the different breeds.
The traditional spay/neuter age of six months as well as the modern practice of pediatric 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.

Consider taking this information to the vets office with you, and if you are going to spay/neuter, consider waiting until the age of two when bone growth, etc. will have stabilized.

[edited 20090828 3:07 - to redo meandering conclusion slightly ]