For decades, the standard approach to spay and neuter in dogs has been to have it done asap – ideally before a female’s first heat cycle or before a male has the opportunity to breed. The given reason for this approach was that it would decrease the pet’s chance of cancer – specifically mammary cancer in the females and testicular/prostatic cancer in the males, but it’s probably more likely that its main motivation was as a means to manage pet overpopulation (a totally different blog post).
The problem with that reasoning was that it failed to take into account whether or not the dog was at a particularly high risk of developing those cancers in the first place, and, moreover, if there were negative impacts of removing the sex organs at such a young age.
I’m incredibly excited about some newly published research from the University of California – Davis College of Veterinary Medicine. This study analyzed the increased risks of various cancers and joint diseases in dogs who were sterilized early vs. those who were not. Their study includes 35 breeds, as these were the breeds which had a large enough sample size to be statistically significant. They DID also evaluate these relationships in mixed-breed dogs, but they will be publishing this research in a separate report.
What Did They Find?
For the majority of breeds evaluated, time of sterilization had no impact on risk of joint disorders or cancers.
HOWEVER, for some specific breeds/sexes, there WAS enough evidence to indicate a statistically significant increase in disease – Australian Cattle Dog (female), Beagle (male), Bernese Mt. Dog (male), Border Collie, Boston Terrier (male), Boxer, Cocker Spaniel, Collie (female), Corgi (male), Doberman Pinscher, English Springer Spaniel (female), German Shepherd, Golden Retriever, Irish Wolfhound (male), Labrador Retriever, Miniature Poodle (male), Standard Poodle (male), Rottweiler, Saint Bernard (female), Shetland Sheepdog (female), and Shih Tzu (female).
They were kind enough to summarize the entirety of their recommendations, based on their findings, in a convenient table! Check out the full article and scroll to Table 1.
What Do I Do With This Information?
As a veterinarian, I’ve always based the time of spay/neuter on a conversation with my client. If my client is not willing to manage an intact pet, we schedule the sterilization between 4-6 months. If my client IS willing to manage an intact pet, I’ve been recommending that they wait until physical and sexual maturity, which of course is later for large-breed dogs than small-breed dogs. Now that I have this handy table, I will share this with my clients as well.
If you are a responsible breeder of one of the at-risk breeds, I would recommend providing this research paper and explanation to your puppy buyers. If you typically write a letter to their future veterinarian, I would include a statement such as, “Based on recent research from the University of California – Davis College of Veterinary Medicine, it is suggested that waiting to spay/neuter [BREED] until [TIMEFRAME] is likely to decrease their risk for joint disorders and/or cancer.”
What About Breeds Not in the Study?
There are, of course, hundreds of breeds that were not able to be included in this study. At this point, we don’t know which of these breeds are at increased risk and which aren’t. Additionally, many dogs are mixed breed or crossbred, and the relationship is likely even more complicated in those individuals because of the variability in their genetics.
My main takeaway points are the following:
1) It is not accurate to uniformly say that spaying/neutering before 6 months of age is in the best interest of the patient or that it’s even safe.
2) The time to spay/neuter is a decision that should be made on an individual basis with each family and their veterinarian. If your family does not agree with your veterinarian on this point, I would recommend that you find another one.
Yours in healthy, responsibly-bred puppies,