Gazette Vet: When to Spay or Neuter?


One of my favorite parts of my job as a veterinarian is the steady stream of puppies and kittens that come into the door. The obvious enjoyment here is that puppies and kittens are always adorable and entertaining. Brand new, soft fur, pudgy legs, and round faces, they are always a pleasure to examine and get to know.

However, I also enjoy witnessing a new and significant relationship start between the owner and the new pet. These babies are going to be with their new parents for the next 10-20 years—that is a significant chunk of any person’s life. To see these very first steps, as each party is getting to know the other, is a joy and honor.

A common question that ultimately comes up for any of these pets is “when should I spay/neuter my pet?” The answer used to be straightforward, but now it is changing.

Here in the U.S., there has been a heavy push to spay and neuter all dogs and cats. This is mainly to curb the unwanted pet population, and generally speaking, I agree with this policy. Head into any shelter or SPCA and you will see way too many stray animals. The need for homes will simply never be met.

“Spaying” refers to removing both the ovaries and the uterus (ovariohysterectomy) of female dogs and cats, whereas “neutering” refers to removing the testicles of male dogs and cats.

I will also add that just like in people, dogs and cats that are “intact” have a very high rate of problems with their reproductive organs when they age. Intact male dogs that are over 10 years old are extremely likely to get prostate infections that can be very difficult to deal with. Intact females over 8 are very likely to get uterine infections (pyometra) after their heat cycles, as well as mammary cancer. My experience with geriatric pets who are not spayed or neutered is that they are very likely to suffer some significant health problems from their reproductive organs.

All that being said, early spay and neuter seems a no-brainer.

However, recent studies over the past 10 years suggest that there may be some unintended consequences to early spay and neuter. A recent study done at the University of California at Davis and published in 2013 looked at a large number of Golden Retrievers and examined the relationship between spaying/neutering and the incidence of a few specific problems including hip dysplasia, ACL tears, and cancer. Hip dysplasia is common in many breeds and leads to hip arthritis when pets are older. ACL tears lead to significant knee arthritis and require surgery. Cancer is, of course, just bad.

This study showed that neutering dogs early increased their risk of getting all of these things.

Whoa. Are we doing something wrong by neutering/spaying our pets? Should we not do this anymore?

Well, before you go spreading a soundbite of “if you spay your dog, they’ll get cancer!”, let’s examine the limits of this study a bit more.

First, one thing that is not known is exactly why these pets are more at risk for getting the orthopedic problems and the increased incidence of certain cancers when they are neutered at an early age. Is it specifically the lack of estrogen/testosterone? Or, is it possible that spayed/neutered dogs are more likely to become overweight and thus overload their joints and have a less healthy body condition. Another study needs to be done that looks at these dogs and splits them in to “overweight” and “not overweight” categories so we can see if a thin, but early-spayed dog is truly at a higher risk for hip or knee problems than a thin, intact dog.

Second, the study defined “early spay/neuter” as dogs neutered before 1 year of age. This category is very broad in my opinion. I would like to compare dogs spayed/neutered before 4-5 months of age, with dogs done after one year of age. Most Goldens are done growing by 10-11 months of age, so it’s probably unfair to group dogs spayed at 11 months in the same category as dogs spayed at four months of age.

Third, the study only looked at dogs from one to eight years of age. Thus, what we are missing is “do dogs who were neutered late or not neutered at all have higher rates of cancer when they are 10?” As I stated earlier, I see a lot of problems with intact dogs who are geriatric, and I think that health has to be considered in the overall decision on when to spay/neuter your pet.

So, like all studies in medicine, this study begs to be applied to our practice decision-making; however, it needs to be interpreted with critical thinking and clinical judgement. In doing that, here are my opinions on when to spay/neuter your pets:

• For cats—always spay and neuter them before 6 months of age. If you wait, you are very likely to have a cat who has some inappropriate urination in the house. Very likely! This is probably one of the number one reasons people give up their cats to a shelter. So, for cats, who have a lower significance with hip dysplasia and knee problems anyway, the decision is very easy: spay/neuter before 6 months.

• For smaller dogs—I tend to recommend spaying/neutering after all of their adult teeth have come and in and all of their baby teeth have fallen out, so around seven months of age. Smaller dogs have a lower incidence of hip and ACL problems and they tend to finish growing much earlier than the large breed dogs. I don’t think we are messing them up by spaying/neutering them at this time. Generally, I don’t like to do them before five months. This just seems early to me; however, I have no scientific data to justify that thought, just judgement and critical thinking.

• For large breed dogs—I tend to recommend that males are neutered around 10-12 months of age and females are spayed anywhere from 9-12 months, depending on if the owners want to deal with the dog going through a heat cycle or not. I tell people why I make this recommendation, namely that I think early spaying/neutering may increase the incidence of orthopedic problems, but I also tell them we have to balance this decision with other factors such as their behavior, their environment, and ultimately the owner’s wishes.

• I tell owners that spaying or neutering dogs does not cause obesity. Owners cause obesity by overfeeding! I always stress the importance of keeping their pets at a healthy weight because being overweight is probably the biggest problem with joint disease.

• I don’t think there is a big downside to waiting until two years of age to spay or neuter. Yes, it’s possible that this can increase their risk for mammary problems or prostate problems when they are older, but I think this risk is fairly low compared to the possible protective benefits of staying intact for a while.

• Late neutering (let’s say after 3-4 years) or not neutering at all has an overall negative effect on a pet’s life. We lose a lot of dogs from mammary cancer, uterine infections, and prostate infections every year. I look at these as mostly preventable problems. Also, spaying and neutering them when they are elderly, to fix a problem, is never easy.

• One more note: I realize the SPCA will usually spay/neuter any pet that comes in before they are adopted out, even sometimes as early as 10-12 weeks. Is the SPCA messing these pets up? Well, I do support the SPCA on their policy. Remember, they have way too many homeless pets and they are doing their part to decrease the homeless pet population as a whole. Early spay/neuter is an effective step for this problem and trying to delay that could very well lead to even more homeless animals. There is simply no perfect answer here and I feel we are very fortunate to have some great shelters in our area.



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