Should I sterilise my pet? If so, when?
We’ve known for a while now that there are a bunch of benign and some down-right nasty things that can affect our pets if we don’t sterilise them3. There is also a whole bunch of more old-school style wisdom regarding a range of possible benefits to leaving your pets unsterilised. So where does the truth lie, and has any more recent research shed light on this?
This post examines some fascinating new research that will surprise many out there.
No seriously, should I sterilise my pet?
Spoiler alert: the answer is still yes. There is no doubt that sterilised dogs and cats live longer on average. They are no longer driven by sexual desires they have no outlet for, they carry no risk of suddenly presenting with a growing belly, and they grow old much more gracefully. No male dog has ever felt “less of a man” as a result of castration, because no dog ever feels “like a man” – these are our views projected onto them. Their lives are far simpler, and far purer.
So it needs to be done at some stage – but when is the best time?
This is where the scientific evidence is getting more interesting. The studies out there vary quite wildly, and many of them have numbers too low to provide much statistical credibility, but the picture is developing! The largest study to date1 investigated the clinical records of 759 golden retrievers and compared the rates of various diseases in early sterilised and non-sterilised dogs. Goldies were chosen because of a high breed incidence of various cancers and various joint problems. The results showed that for several of the less common cancers, as well as cruciate ligament injury and hip dysplasia, early sterilisation increased the risk of disease!
The effect of sterilisation on the incidence of mammary tumours has been known for a longer period of time2 and is summarised here:
|Reproductive Status at Time of sterilisation||Mammary Tumor Risk|
|Never in estrus||0.5%|
|In estrus 1 time only||8%|
|In estrus ≥2 times , regardless of age
and ≤2.5 years of age
and >2.5 years of age
Clearly this study shows a dramatic benefit in early desexing. But what else is affected? A range of tumours have been shown to occur with a higher incidence in dogs sterilised before 12 months of age. As noted above, much of this information relates purely to golden retrievers and may not be applicable to other breeds. However, there is a general sway of evidence that suggests remaining intact for at least the first year provides some tangible benefits to male and female dogs:
|Condition||Effect of spaying on Relative Risk||Effect of Castration on Relative Risk|
|Overall longevity||Mild increase in longevity||Mild increase in longevity|
|Obesity||Moderate increase||Moderate increase|
|Cranial cruciate ligament disease||Moderate increase*||Moderate increase*|
|Hip dysplasia||Mild increase*||Mild increase*|
|Mammary tumors||Marked decrease*||N/A|
|Uterine, ovarian, vaginal tumors||Prevents||N/A|
|Perianal gland tumors||N/A||Marked decrease|
|Prostatic carcinoma||N/A||Mild increase|
|Lymphoma||Mild increase||Mild increase*|
|Mast cell tumors||Mild increase||N/A|
|Hemangiosarcoma||Mild increase*||Mild increase|
|Osteosarcoma||Mild increase*||Mild increase*|
|Transitional cell carcinoma||Mild increase||Mild increase|
|Urinary sphincter mechanism incompetence||Moderate increase*||N/A|
|Benign prostatic hyperplasia||N/A||Marked decrease|
|Perineal hernia||N/A||Moderate decrease|
*Age at time of surgery may be important.
Ok, so that all mostly confused me. What does it mean?
The upshot of all of this is that there really is no right answer. There is no perfect time to sterilise your pet. There are good arguments not to sterilise very early and there and really good arguments not to leave it too late. For me the outer bounds are clear –
- 3 months, as some welfare organisations and breeders insist on, is far too early
- 6 months, as I used to recommend, is also too early in many situations
- 7 years plus is too late
- A male dog who is starting to develop troublesome “boy” behaviours such as peeing on furniture or humping soft toys and children should be sterilised long before these behaviours become habituated. A male dog who has done this for more thana few months may never stop even if he is sterilised!
- A female pet (of any species) who appears to have health problems associated with coming into season should be sterilised without delay at any age
In the more straight-forward situations with average healthy pets I feel that sterilising your pets should be done sometime between 1 and 2 years of age. I recommend earlier for smaller animals and for any showing problems (as noted above), and later for larger dogs.
Please feel free to add your comments below. When was your pet desexed? Do you now think it was too early or too late?
- de la Riva et al. Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers. 2013, https://doi.org/10.1371/journal.pone.0055937
- Schneider et al. Factors Influencing Canine Mammary Cancer Development and Postsurgical Survival. 1969, https://doi.org/10.1093/jnci/43.6.1249
- Fossum et al. Small Animal Surgery. 2013, Elsevier