Dog Neutering or Spaying A Dog: Pros and Cons (Backed by Science)


Table of Contents

  • What is Spaying and Neutering of Dogs
    • How to Prepare Your Dog Before Spaying or Neutering
    • What to Pay Attention to and Expect After the Surgery
  • Why Spay or Neuter Your Dog
  • What Do Science and Experts Say
    • A quick science-based overview of what we know today:
  • Dog Spaying: 3 Pros and 3 Cons
    (female dogs)

    • 1 PRO of spaying your dog: Heat Period Reduction
    • 2 PRO of spaying your dog: No Doggy Pregnancy
    • 3 PRO of spaying your dog: Less Risk of Cancers
    • 1 CON of dog spaying: Hypothyroidism and Weight Gain
    • 2 CON of spaying your dog: Cancers and Complications
    • 3 CON of spaying your dog: Sterilization and Use of Anesthesia
  • Benefits and Downsides of Neutering Your Dog: Pros and Cons (male dogs)
    • 1  PRO of neutering your dog: Reduction of “Male” Behavior
    • 2 PRO of neutering your dog: Better Prostate Health
    • 3 PRO of neutering your dog: Control of Breeding
    • 1 CON of neutering your dog: Hypothyroidism and Weight Gain
    • 2 CON of neutering your dog: Dementia and Bone Problems
    • 3 CON of neutering your dog: Risks of Anesthesia
  • Take-Home Message
  • Common Questions About Spaying A Dog
    • Do Female Dogs Change After the Spaying Procedure?
    • What Age Should a Dog Do the Procedure?
    • How Long Does It Take a Dog to Recover From Being Spayed?
    • What Happens When You Spay a Female Dog?
    • Do Dogs Bark Less After Spaying?
    • Is there a Reason to Spay Your Dog Other Than to Prevent Pregnancy? 
    • References
    • READ NEXT: 15 Cheap Ways To Prevent Most Common Health Issues in Dogs
    • Related

You probably think about neutering or spaying your dog, but you’re not 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.

This article will look at the advantages and disadvantages of spaying and neutering dogs based on what veterinarians say and 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 them with evidence and expert opinions.

Dog neutering is a grave decision; you should not take it lightly.

I also recommend listening to 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).

RELATED: How Neutering Dogs May Lead to Cognitive Impairments

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 sterilization methods, most often used with dogs, but many other animals go through this.

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

How to Prepare Your Dog Before Spaying or Neutering

Before the surgery, your vet will typically want to confirm that your dog is healthy. Your dog will also typically have to fast before the surgery to prevent nausea from the anesthesia. 

What to Pay Attention to and Expect After the Surgery

Your vet will ask you to restrict your dog’s activity 7 to 10 days after the surgery. Expect your dog not to eat as much the first day after surgery, but this should quickly change. You will have to bring your dog back in a week or two, so the vet can remove the stitches and check the incision.

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

Why Spay or Neuter Your Dog

Most commonly cited two main reasons for dog neutering are:

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 to prevent further problems to an already huge overpopulation of domestic animals.

Some states are even required 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:

Several dogs in the United States. Credit: Humane Society

The numbers of domesticated pets in the US are growing, and so do the numbers of animals brought into shelters, which clearly 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 Science and Experts Say

As I mentioned above, most veterinarians and other experts, as well as state laws, see neutering or spaying your dog as a good thing and 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.

Many studies have been coming out over the last five years showing how neutering and spaying dogs may actually be naughty for their health.

A quick science-based overview of what we know today:

  • Early dog neutering doubles the chance of hip dysplasia (1)
  • Early dog 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 the 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.”

– 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 evidence.

Statistically, it used to be that there are more pros than cons to deciding to neuter or spaying your dog. The surgery is still highly recommended by vets for various 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.

RELATED: 8 Laws All Dog Owners Should Be Aware Of

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

PRO of spaying your dog: Heat Period Reduction

Dog spaying will prevent periods of your baby girl 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 desire to wander and look for a mate, often resulting 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 about leaving her alone in the yard or taking her for walks.

According to veterinarians, she will also be a much cleaner, calmer, and more affectionate dog.

PRO of spaying your dog: No Doggy Pregnancy

Spaying a dog prevents your female canine from getting pregnant.

Whether intentionally or accidentally, Breeding can become a large 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 additional 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.

PRO of spaying your dog: Less Risk of Cancers

Spaying a dog will eliminate the risk of your female dog developing cancer of her uterus, cancer of ovaries, or reproductive tract. When these organs are removed, you will have fewer worries about 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 valid reason to 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 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.

READ: 15 Tips on Dog Pregnancy and Whelping

CON of dog spaying: 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 an 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 why your dog is becoming overweight, and eventually, you might need to start dealing with dog obesity.

Spayed a dog often starts gaining weight at an increased rate after the procedure, most likely due to changes in metabolism and hormonal structure.

You can avoid weight gain and dog obesity issues 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.

CON of spaying your dog: Cancers and 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 the 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, health complications can worsen for the dog even more. 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.

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, most 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 meager death rate.

RELATED: 30 Myths That Many Dog Owners Still Believe

Benefits and Downsides of Neutering Your Dog: Pros and Cons (male dogs)

PRO of neutering your dog: Reduction of “Male” 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.

Reduce Aggression

Also, a neutered dog will have a reduced level of aggression and dominant 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.

Reduce Sexual Desires

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 more mellow and not seeking a female in heat, they are calmer and stay closer to home.

PRO of neutering your dog: Better Prostate Health

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 and improving a dog’s testicular health.

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 the progression of tumors (11).

Moving along, male dogs can sometimes experience the case of a 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.

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 a strange female dog mostly because of dogs and cats’ current overpopulation 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.

CON of neutering your dog: Hypothyroidism and Weight Gain

Similar 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 differently, and hormonal levels are affected, resulting in lower thyroid levels, resulting in very rapid weight gain and potentially dog obesity.

While you can treat hypothyroidism with medication after you consult with a vet and confirm that it’s definitely the case, you must address your dog’s weight gain 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.

They will also need regular exercise and constant monitoring to see how this program has affected your pet.

CON of neutering your dog: Dementia and Bone Problems

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

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 lives, or if the process was done poorly, studies show a high risk of hip dysplasia, problems with ligaments, and even the potential to develop bone cancer known as osteosarcoma, according to the above-mentioned studies.

The reason for all these bone and joint-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.

CON of neutering your dog: Risks of Anesthesia

Again, same as spaying your dog, neutering a male canine means that your pet will have to undergo surgery requiring 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 meager 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 and whether it’s essential to fix your dog.

Most recent studies now show many more disadvantages to a dog neutering than we previously thought.

However, there are also definite and proven advantages to fixing your dog.

Making a good decision in this matter is complicated to make.

Overall, it seems that it still is worth de-sex your dog as the pros of sterilization outweigh the cons.

But that said, 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 spayed much too early, increasing the risk of further health problems and complications.

Concerning yourself with dog spaying or neutering a dog while your pet is still a young puppy is a good way to plan, but not rush into that.

Common Questions About Spaying A Dog

If you still find yourself wondering what to do, consider the following questions and answers. 

Do Female Dogs Change After the Spaying Procedure?

It is common for female dogs to have more consistent behavior after doing the procedure. This comes from the lack of hormonal changes associated with their cycle. 

What Age Should a Dog Do the Procedure?

Most experts agree that you should spay your dog at around four to six months old. In some situations, your vet may suggest doing so earlier or later. 

How Long Does It Take a Dog to Recover From Being Spayed?

On average, the incision from neutering or spaying your dog should heal around 10 to 14 days. 

What Happens When You Spay a Female Dog?

Spaying a female dog means removing her reproductive organs. The procedure always removes her ovaries and typically also removes the uterus. Neutering is the term used to describe removing the reproductive organs of a male dog. 

Do Dogs Bark Less After Spaying?

It is common for dogs to bark less after being spayed or neutered. They may also have reduced aggression and do not wander as much. This comes from the reduction in activity that is typical after the procedure. 

Is there a Reason to Spay Your Dog Other Than to Prevent Pregnancy? 

Your vet may also suggest spaying your dog to treat phantom or false pregnancy, abnormal cycles from ovarian cysts, cancer, or uterine infections. It may also be part of your dog’s diabetes treatment.


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Footnotes, study citations, and further reading:


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