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Should I Desex my Dog?

Updated: Aug 7, 2019

Whether to desex or neuter your male dog is one of the most important decisions you as a pet owner will make. It’s not a simple decision; there are pros and cons plus a good amount of misinformation which utterly defy a simple answer.

If you are interested in this subject, please try to read the whole article, which may be the most important I have written. Avoid sensational headlines, take the time to absorb the detail and you will already be better than 99% of the opinion-makers online.

At the end, you will not only have the best and most up to date understanding of this subject, but you will see how easily good science can be turned into bad advice.

Worryingly, among the genuinely good articles on desexing are many who misrepresent or misread the scientific literature in support of their own ideas. Make no mistake; the consequences of the wrong decision can be disastrous.

‘Why I should not desex my dog’

This blog began innocently enough. If I had any idea how big a task it would become I might never have dared to start. The owners of a male puppy told me they had been doing their own online research and had decided not to desex. I told them my views and made sure they knew that I respected their decision, but naively I googled ‘Why I should not desex my dog’ just to see what they had been reading.

Straight away I found results which truly shocked me and made me question my own knowledge. Most of the top search results were strongly against desexing and made convincing claims of the harm being caused. Many pages referenced or linked an authoritative article titled Early Spay-Neuter Considerations for the Canine Athlete: One Veterinarian’s Opinion by Chris Zink DVM, PhD, DACVP, DACVSMR.

This article’s title suggests it is about the debate between neutering at 8 weeks and neutering at the traditional date, usually 6-7 months. However, reading the article leaves no doubt that the author is arguing against desexing at all.

The article cites high-quality scientific papers from leading journals to support its statements. I am a veterinarian quite accustomed to reading journal articles and I finished the article convinced that these statements were true. Several sleepless nights followed as I worried that I had been inadvertently giving bad advice to dog owners.

The Science Behind Desexing Dogs

There is only one way to check a scientific review author’s conclusions; by reading the original articles. The scandal of modern science is that it is not possible for 99.9% of the population to do this. Due to copyright restrictions, the full text of journal articles is only available to paid subscribers, usually university-based academics. Many people are trying to fight this, as it goes to the heart of why science is so poorly reported in the media. Here is the cause for which the internet hero Aaron Swartz lost his life. Read his story at Aaron Swartz Wikipedia article then please come back!

Luckily, a colleague with full journal access came to the rescue. He promised me that if I was having trouble sleeping, reading original scientific papers was definitely a cure for insomnia. However, I read these papers with a growing sense of astonishment. While most of Chris Zink’s statements are factually correct, there was usually another more logical interpretation or important extra information which had not been discussed.

Follow this link for a guide to doing your own research into neutering or anything else.

The Facts: Desexed vs Undesexed Dogs

I will go through each of her conclusions one by one.

That desexed dogs are more likely to be obese than undesexed dogs. This is true (Lund et al). It is probably the most reliably observed negative association with neutering and every owner should be aware of the risk. Dogs seem to have an increased drive to eat following desexing, and simultaneously a reduced food requirement. Obesity is then associated with a wide variety of important diseases and reduced lifespan (Kealy et al).

Obesity is entirely preventable by controlled feeding. If you do not feel capable of measuring and managing your dog’s food intake and body condition, then it may be better to not neuter. However, for the majority of dog owners, this management is no different to how they have been feeding their dog all along, and all they need to do is reduce the amount fed after desexing. For more help, visit our page on helping an overweight dog lose weight.

That desexed dogs have delayed growth plate closure and are taller than undesexed dogs. This is probably true, uncontroversial and not associated with any known problems.

That desexed dogs have a higher prevalence of cranial cruciate ligament disease (CCLD) and hip dysplasia (HD) than sexually intact dogs. Tricky one. This is a complex discussion and there is no easy answer. There are six often-cited studies showing a link between neutering and hip dysplasia or cruciate ligament disease. I’ve asterisked (*) them in the references at the end.

The problem is always the differences in body weight. Not one of these observational studies is controlled for weight; that is, the desexed groups are heavier, and weight is a significant risk factor for CCLD and HD. We need a study that compares groups of equal body condition to answer this question adequately.

To be fair, it is very hard to design a study that can’t be faulted, and there does seem to be a trend towards HD and CCLD being more common in desexed dogs. As a consequence, these findings have influenced the best age to desex and neuter dogs. It varies with breed and sex but a quick summary is that breeds susceptible to joint problems are now being deferred to 12 months of age.

There is an abnormal angle of the stifle increasing stress on the CCL. True, Tibial