Pros & Cons of Neutering or Spaying

Pros and Cons of Neutering or Spaying Your Dog (Backed by Science)

Diana Beth Miller

You're probably thinking about neutering or spaying your dog, but you're not so sure if this is a good idea. Know that you're not alone in this, because many pet owners are given conflicting information on whether neutering and spaying dogs is necessary, and whether it's good or bad for their health.

In this article, I will take a look at the advantages and disadvantages of spaying and neutering dogs based on what veterinarians say as well as the most current research.

Many dog owners find themselves contemplating on this decision for a while, and rightfully researching the Internet for all kinds of answers to common sense questions:

  • What are the pros and cons of neutering or spaying a dog? 
  • Should I leave my dog as nature has intended him/her to be?
  • What do dog experts and veterinarians think about this process?
  • Do all other dog owners spay or neuter their dogs?
  • What does science have to say about neutering or spaying your dog?

Rest assured, these are all valid concerns of a responsible pet owner, and I will try to address of all of them using evidence and expert opinions on the matter. Spaying or neutering a dog is a very serious decision, and you should not take it lightly.

I also recommend listening our editor Samatha's recent podcast episode on the pros and cons of neutering/spaying dogs and how people view this all-important surgery (below).

Pros and Cons of Neutering or Spaying Your Dog
Should You Do It?

What is Spaying and Neutering of Dogs?

Let's start at the beginning to understand what spaying and neutering dogs really means, what this surgery looks like and what it entails for you and your pet.

Both neutering and spaying refer to the most common methods of sterilization of animals, most often used with dogs, but many other animals go through this as well. Veterinarians usually call this procedure either de-sexing dogs, or fixing dogs.

One may argue that the term “fixing” a dog may be misleading or even ironic, since the evidence on whether it should or should not be done is not conclusive. More on this later.

What is neutering? Neutering is the de-sex procedure of male dogs where their testicles (or gonads) are removed. The actual removal of male dog's testicles is called Castration.

What is spaying? Spaying is a similar procedure of sterilization for female dogs. In this case, a female dog's ovaries and uterus are removed – it's called Ovariohysterectomy.

Even though terms neutering and spaying are used in veterinary medicine, most often the term “neuter” will refer to the removal of reproductive organs in the dog for both sexes. Colloquially, neutering doesn't necessarily mean that it applies to male dogs alone.

LISTEN: Podcast on Pros & Cons of Neutering/Spaying Dogs

Why Spay or Neuter Your Dog?

Most commonly cited two main reasons for spaying or neutering a dog are:

  1. Control the population growth of dogs;
  2. Eliminate or decrease the chance of a dog developing certain types of diseases.

Overpopulation of dogs. In North America, most animal shelters, veterinary clinics and humane societies highly recommend (read: force) pet owners to spay or neuter their dogs so as to prevent further problems to an already huge overpopulation of domestic animals.

Some states even require by law to spay or neuter dogs before they can be adopted.

The problem is real, however. The Humane Society of the United States cites that 6 to 8 million pets are brought to animal shelters every year:


The numbers of domesticated pets in the US are growing, and so do the numbers of animals brought into shelters, which clear pose a huge issue on many different levels.

Neutering and spaying are also performed for many other animals, but dogs are the most common recipients of this unpleasantly sounding surgical procedure. Dog owners will usually have their puppies spayed or neutered around the age of 6 months or earlier.

Neutering and spaying of dogs are done under general anesthesia, so your canine won't feel a thing when a surgical incision is performed.

What Do Experts Say and What Does Science Show?

As I mentioned above, most veterinarians and other experts, as well as state laws, see neutering or spaying your dog not only as a good thing, but as a necessity. It has been like this for decades.

However, most recent research has been calling this surgical procedure into question as more evidence emerges.

There has been a number of studies coming out over the last five years that show how neutering and spaying dogs may actually be extremely bad for their health.

Here's a quick science-based overview of what we know today:

  • Early neutering of dogs doubles the chance of hip dysplasia (1)
  • Early neutering increases joint disorders in dogs by four times (2)
  • Neutering dogs triples the risk of several joint problems in GSDs (3)
  • Neutering decreases longevity in Rottweilers (4)
  • Neutering increases a chance of cancer in dogs (5)

With this new research and more on the horizon, veterinarians and scientists are beginning to reconsider their stance on neutering and spaying dogs. However, just like with research on the pros of neutering a dog, evidence for the cons of neutering dogs in general is still not conclusive and requires more biological research.

One thing is clear, however:

We must definitely reconsider the time of spaying and neutering dogs. Based on all the scientific data, it is clear that early neutering has more cons than pros.

It appears that spaying or neutering your dog much too early is very likely to cause joint disorders, and potentially obesity and maybe even cancer. Furthermore:

“In addition to dogs suffering pain from joint disorders, the condition may also disqualify the dog as a working partner in military and police work. We hope these findings provide evidence-based guidelines for deciding the right age to neuter a puppy to reduce the risk of one or more joint disorders,” says Prof. Benjamin Hart from UC Davis School of Veterinary Medicine (source)

With all of the above in mind, you should definitely not rush into spaying or neutering your dog. However, there are advantages to this procedure, some of which are based on scientific research while others still do not have conclusive enough evidence.

Statistically, it used to be that there are more pros than cons to making the decision of neutering or spaying your dog. The surgery is still highly recommended by vets for a variety of different reasons, but now we need more evidence than we currently have.

Let's take a look at the consensus of the pros and cons of spaying and neutering dogs.

Spaying Your Dog: 3 Pros and 3 Cons
(female dogs)

1          PRO of spaying your dog: Heat Period Reduction

Spaying your female dog will prevent periods of her being in heat.

When a female dog is in heat, her genitals swell and she lets out a scent that can be traced for up to a mile and attract unwanted attention from male canines.

Your female will also have less of a desire to wander and look for a mate, which would often result in additional dog behavior problems like escaping from home and getting lost.

When in heat, a female dog can have bloody discharge that will stain her coat and your furniture, her own dog bed or dog crate. Having a dog in heat when living in an apartment maybe not be the most pleasant thing.

By spaying your female canine you won't have to worry when leaving her alone in the yard or when taking her for walks. She will also be a much cleaner, calmer and more affectionate dog, according to veterinarians.

2          PRO of spaying your dog: No Doggy Pregnancy

Spaying your dog prevents your female canine from getting pregnant.

Breeding, whether intentionally or accidentally, can become a largely financial and time-consuming burden for dog owners, which also comes with health risks and responsibilities.

When caring for a pregnant dog, you should expect an increase in your vet bills and dog food and care supplies. There is also a small risk of death during birth or right after.

Furthermore, any complications during the pregnancy period of your dog may also result in even more veterinary care bills and addition health risks for the newborn puppies.

If you decide to find homes for your new puppies, that may prove to be much harder than you think. Normally, owners must keep the puppies with their mother until they are about 6 weeks old, and then try to find a home for them.

In the most basic sense, it is far less expensive to have your dog spayed to prevent canine pregnancy than it would be to have her get pregnant and get a litter of puppies.

3          PRO of Spaying Your Dog: Eliminated Risk of Canine's Uterus and Ovaries Cancer

Spaying your dog will eliminate the risk of your female dog developing cancer of her uterus, ovaries and reproductive tract. When these organs are removed, you will have less things to worry about in terms of your dog's health.

Even though these types of cancers are already very uncommon (6) for female dogs to develop throughout their lives, many veterinarians advise that it's still a very valid reason to proceed with spaying your dog, and it doesn't hurt to be safe.

Aside from the above mentioned cancers, spaying reduces the risk of your female dog getting breast cancer if she is spayed before she reaches 2.5 years old. The more heat periods she has, the greater will be the risk that she may be developing breast cancer.

Finally, spaying your female dog protects her from getting uterine infections. It's been observed (7) that one in four unspayed female dogs will contract a uterine infection. If left untreated, this disease may very well kill your pet.

1          CON of Spaying Your Dog: Hypothyroidism and Weight Gain

Because your dog's endocrine system is affected, one of the more known side effects of spaying your dog is the risk of hypothyroidism. Low thyroid levels in a female canine will result in weight gain and obesity which is difficult to fight even with adequate diet.

Your dog may also become lethargic, tired and start losing hair. Veterinarians recommend special medication to deal with hypothyroidism in dogs.

As the above discussed study shows, this condition may be the reason for your dog becoming overweight, and eventually you might need to start dealing with dog obesity.

Very often, spayed female dogs start gaining weight at an increased rate after the procedure, most likely due to changes in metabolism and hormonal structure.

Weight gain and dog obesity issue can be avoided by using an adequate amount of regular exercise, understanding dog food and proper nutrition and otherwise providing your female canine with a healthy and stress-free lifestyle.

2          CON of Spaying Your Dog: Canine Cancers and Other Complications

It has been observed in the above discussed studies that spaying your dog increases the risk of deadly canine cancers, including lymphoma and hemangiosarcoma.

Hemangiosarcoma disease in particular affects dog's spleen and heart, which normally would've been protected by your female canine's reproductive organs.

Additionally, if the spaying surgery is done wrong or at the wrong age, even more health complications can come through for the dog. For example, after spaying your dog, you might have her run the risk of uneven bone growth, bone cancer, urinary incontinence, and this procedure can also affect the appearance of her private parts.

Finally, abnormal vulvas can trap bacteria and cause dermatitis, vaginal infections, urinary tract infections, all of which should be considered.

3          CON of Spaying Your Dog: Sterilization and Use of Anesthesia

In its technical term, spaying is the surgical procedure of sterilization. That means your dog will never be able to become pregnant and there's no going back with this.

However, given the overpopulation of dogs today with millions of them being stray, homeless, living in shelters or being euthanized, majority of pet advocates see this as an advantage of spaying a dog.

Because the procedure itself has to be done using general anesthesia, there's a possibility that your pet will react poorly to this medication (7).

Some studies have shown (8) that about 1 in 5 dogs will have complications after surgery under general anesthesia. However, most of these complications are not serious health issues and they do have a very low death rate.

Neutering Your Dog: 3 Pros and 3 Cons
(male dogs)


1          PRO of Neutering Your Dog: Reduction of “Male-type” Behavior

Neutering your male dog helps in reducing his desire to “mark” his territory.

You may have noticed your dog’s need to lift his leg and spray. Often a dog will even mark inside your home. Neutering your male will help to reduce his obsession with this behavior.

Also, a neutered dog will have a reduced level of aggression and dominate behavior. Since neutering your dog involves removing the main source of testosterone, it can help mellow out your male dog, according to research (9).

Because of the lower level of testosterone and less aggression, neutered canines tend to be more affectionate and gentle than those that haven't been “fixed.” It also helps in protecting your male from non-neutered male dogs seeing him as a rival.

Your dog will be less likely to get into fights with other dogs, canine packs or strays in the neighborhood, which saves you the cost of vet bills or the pain of finding your pet injured.

After neutering your dog, you'll reduce his sexual desires. He is less likely to hump other pets or objects. It will also help in keeping a dog from chasing a female in heat.

If your dog is not neutered, he will be able to sense a female in heat from up to a mile away and can get agitated. If he gets loose, he will try to track down the scent.

Neutered dogs are less likely to have the desire to roam as well. Since they are mellower and not seeking a female in heat, they are calmer and stay closer to home.

2          PRO of Neutering Your Dog: Less Prostate and Testicle Health Problems

Experts used to believe based on previous studies that not only does neutering help in reducing unwanted behaviors in a dog, but it also helps in reducing prostate problems.

Prostate problems can occur in 80% of non-neutered males, based on one study (10). Issues can include an enlarged prostate in dogs, prostate cysts and prostate infections. But another study has shown that castration may increase progression of tumors (11).

Moving along, male dogs can sometimes experience the case of skin disease known as perianal fistula, or anal fistula. This nasty condition develops carbuncles around your dog's anus and is often very complicated to treat. If neutered, the risk is highly reduced.

Testicular cancer can also be eliminated by neutering. Even though only 7% of non-neutered males get testicular cancer, having your male dog neutered removes the risk.

3          PRO of Neutering Your Dog: Control of Breeding

Finally, neutering keeps your dog from breeding, as I have mentioned above.

Many pet advocates, veterinarians, experts, humane societies and even lawyers agree that it is irresponsible to allow your male dog to breed with strange female dog mostly because of the current overpopulation of not just dogs, but also cats and other pets.

Also, you would have no idea how the new puppies are being treated or if they are safe. While you may not have to shoulder any of the responsibility of the new litter, if you choose to help, there is the cost of pet food and veterinary care bills.

1          CON of Neutering Your Dog: Hypothyroidism, Weight Gain and Canine Obesity

Similarly to spaying your dog as a female, neutered male dogs can experience the case of hypothyroidism, and studies have shown that neutering will almost triple the risk of obesity, as was discussed above.

Once castrated, a male dog's endocrine system starts to function in a different way and hormonal levels are affected, which results in lower levels of thyroid, which then results is very rapid weight gain and potentially dog obesity.

While hypothyroidism can be treated with medication after you consult with a vet and confirm that it's definitely the case, your dog's weight gain must be addressed separately.

Most dog owners will need to start feeding their dogs substantially less often, put them on a weight loss diet, use low-calorie foods and healthy dog treats. Regular exercise will also be needed as well as constant monitoring to see how this program has affected your pet.

2          CON of Neutering Your Dog: Canine Dementia and Bone Problems

Neutered dogs run the risk of developing a canine version of dementia, which is actually called geriatric cognitive impairment.

If this happens, your dog will start forgetting things he used to know, become disoriented wherever he is, even if it's the house where he has lived for years previously.

Dogs with dementia will usually start interacting differently with humans and completely forget all the obedience training they've gone through. It's similar to human dementia.

For canines who were neutered at the wrong age in their life, or if the process was done poorly, there's a high risk of hip dysplasia, problems with ligaments and even potential to develop bone cancer known as osteosarcoma, according to above mentioned studies.

The reason for all these bone and join related diseases is because male dog's reproductive organs are responsible for producing a sufficient amount of hormones and helping with the development of those body parts.

3          CON of Neutering Your Dog: Anesthesia Risk

Again, same as with spaying your dog, neutering a male canine means that your pet will have to go through surgery which requires anesthesia.

Therefore, there's a chance that your male canine will react poorly to anesthesia itself and as previously indicated, 1 in 5 dogs may have further health complications after surgery under general anesthesia.

However, most of these complications will not be very serious with a very low death rate. See this section under “spaying your dog” above for more.

Take Home Message

After we've taken a look at all the pros and cons of spaying or neutering your dog, it's clear that we still need more conclusive evidence on how to view this procedure.

Most recent studies now show that there are a lot more disadvantages to fixing your dog than previously thought. However, because there are definite advantages to this procedure, making a good decision in this matter becomes very difficult.

Overall, it seems that it still is worth to de-sex your dog, but the most important thing to keep in mind is to do it at the right time.

Based on all the evidence we currently have, most dogs are neutered or spaying much too early, and this increases risk of further health problems and complications.


Click here to see study citations and references

Footnotes, study citations and further reading:

  1. Torres de la Riva, G., Hart, B. L., Farver, T. B., Oberbauer, A. M., Messam, L. L. M., Willits, N., & Hart, L. A. (2013). Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers. PLoS ONE, 8(2), e55937.
  2. Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2014). Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers. PLoS ONE, 9(7), e102241.
  3. Hart, B. L., Hart, L. A., Thigpen, A. P. and Willits, N. H. (2016), Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence. Vet Med Sci, 2: 191–199. doi:10.1002/vms3.34
  4. Waters, D. J., Kengeri, S. S., Clever, B., Booth, J. A., Maras, A. H., Schlittler, D. L., & Hayek, M. G. (2009). Exploring mechanisms of sex differences in longevity: lifetime ovary exposure and exceptional longevity in dogs. Aging Cell, 8(6), 752–755.
  5. Zink MC1, Farhoody P, Elser SE, Ruffini LD, Gibbons TA, Rieger RH. Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas. J Am Vet Med Assoc. 2014 Feb 1;244(3):309-19. doi: 10.2460/javma.244.3.309.
  6. Patnaik AK1, Greenlee PG. Canine ovarian neoplasms: a clinicopathologic study of 71 cases, including histology of 12 granulosa cell tumors. Vet Pathol. 1987 Nov;24(6):509-14.
  7. Pollari, F. L., & Bonnett, B. N. (1996). Evaluation of postoperative complications following elective surgeries of dogs and cats at private practices using computer records. The Canadian Veterinary Journal, 37(11), 672–678.
  8. Pollari FL1, Bonnett BN, Bamsey SC, Meek AH, Allen DG. Postoperative complications of elective surgeries in dogs and cats determined by examining electronic and paper medical records. J Am Vet Med Assoc. 1996 Jun 1;208(11):1882-6.
  9. Heidenberger E1, Unshelm J. [Changes in the behavior of dogs after castration]. Tierarztl Prax. 1990 Feb;18(1):69-75.
  10. Bryan JN1, Keeler MR, Henry CJ, Bryan ME, Hahn AW, Caldwell CW. A population study of neutering status as a risk factor for canine prostate cancer. Prostate. 2007 Aug 1;67(11):1174-81.
  11. Teske E1, Naan EC, van Dijk EM, Van Garderen E, Schalken JA. Canine prostate carcinoma: epidemiological evidence of an increased risk in castrated dogs. Mol Cell Endocrinol. 2002 Nov 29;197(1-2):251-5.


© Yorkies United 2015-2017