Were You Smarter Than a Vet Student About Neutering Dogs?

Photo Credit: ScottBecker, Thanks to everyone who took this quiz. There were oodles of you! Congrats to Dale Manley from Moline, Illinois who won himself a book. He asked me if he was selected because he had so many correct answers. No, Dale you were just lucky!

The answers below provide some clear-cut evidence that neutering, particularly when performed at a young age, may cause more harm than good. In light of this new information it is imperative to remember these three things:

  1. Until something better comes along, neutering remains the mainstay strategy in the battle against pet overpopulation. The information below does not in any way, shape, or form, suggest that neutering should not be performed to prevent unwanted litters of puppies.
  1. The breed-specific studies cited below are applicable to those breeds only. Whether or not the data can be extrapolated to other breeds is anyone’s guess. Had I a magic wand, I would order up such studies for all varieties of dogs.
  1. Most dogs in shelter and rescue situations are neutered before adoption is allowed. Should you adopt an intact dog (one who is not neutered) I encourage you to decide if and when to neuter only after talking with your veterinarian and carefully evaluating all the pros and cons as they apply to your individual dog.

1.  The term “neutering” refers to:

a.       Castration.

b.      Ovariectomy (removal of the ovaries but not the uterus).

c.       Ovariohysterectomy (removal of the ovaries and the uterus).

d.      All of the above.

By definition, neutering is the removal of an animal’s reproductive organs and applies to males and females.

2.  Pyometra (pus within the uterus) does not occur in:

a.       Dogs less than two years of age.

b.      Dogs who are being used for breeding.

c.       Dogs who are not being used for breeding.

d.      Dogs who have been spayed by ovariectomy (removal of the ovaries but not the uterus).

Pyometra can occur in any age dog, although the incidence in youngsters is quite low. Pyometra can also occur whether or not the dog is being used for breeding. The exception might be the dog who is bred and conceives with every single heat cycle- the kind of thing that happens in puppy mills….. don’t even get me started! Reproductive hormones produced by the ovaries trigger the development of pyometra. A dog without ovaries cannot develop pyometra, even if she still has a uterus.

3.  Male Golden Retrievers neutered before one year of age have an increased incidence of:

a.       Hip dysplasia.

b.      Torn cruciate ligaments.

c.       Lymphosarcoma (a common type of cancer in Golden Retrievers).

d.      All of the above.

A study published in 2013 evaluated 759 Golden Retrievers between one to eight years of age. When early-neutered dogs (neutered before one year of age) were compared to late-neutered (neutered after one year of age) and intact dogs, the following significant differences were found:

  • Early-neutered males had a 10.3% incidence of hip dysplasia compared to a 5.1% incidence in intact males. There were no significant differences found amongst the female population.
  • Early-neutered male and female dogs had a 5.1% and 7.7% incidence of cruciate ligament tears, respectively. The intact population of Golden Retrievers had zero cruciate ligament tears.
  • Early-neutered males had a 9.6% incidence of lymphoma. Intact males had a 3.5% incidence of this disease. There were no significant differences found amongst the female population.
  • Late neutered female dogs had a 7.4% incidence of hemangiosarcoma (another devastating type of cancer that is common within the breed), compared to a 1.6% incidence in intact females and a 1.8% incidence in early-neutered females. There were no significant differences found amongst the male population.

4.  Rottweilers neutered before one year of age have:

a.       The same average lifespan as unneutered Rottweilers.

b.      An increased incidence of bone cancer later in life.

c.       Much the same conformation (body size, shape, and structure) as unneutered Rottweilers.

d.      All of the above.

Two Rottweiler studies have provided a wealth of information. The first study demonstrated that male and female Rotties neutered before one year of age had a 3-4 times greater incidence of osteosarcoma, a form of bone cancer that is usually fatal and very common in the breed.

The second study documented that intact female Rottweilers were more likely than their male counterparts to achieve exceptional longevity (13 years of age or older). However, spaying before four years of age eliminated this longevity advantage.

Dogs neutered before a year of age do achieve different adult conformation (size and body structure) compared to dogs neutered later in life or left intact. This is particularly true for the larger breeds who tend to reach maturity at a later age. When reproductive hormones arrive on scene (puberty), they signal a number of changes in the body one of which is closure of growth plates, the areas within bones that are responsible for causing lengthening. When the signal from reproductive hormones is missing, as is the case for dogs neutered prior to puberty, the result is a longer-legged more “spindly” appearing critter.

5.  Neutered Vizslas are: 

a.       Less likely to develop cancer.

b.      Less likely to have behavioral issues.

c.       Less likely to have prostate gland disease.

d.      All of the above.

Castration dramatically reduces the incidence of noncancerous prostate gland diseases such as bacterial prostatitis and benign prostatic hyperplasia (BPH). Neutering does not prevent prostate gland cancer, however, compared to other forms of prostate gland disease, cancer is uncommon.

Findings from a 2014 study of 2,505 Vizslas demonstrated an increased incidence of several behavioral issues and varieties of cancer (hemangiosarcoma, lymphoma, and mast cell cancer) in the neutered dogs compared to their intact counterparts.

6.  Labradors neutered before six months of age have an increased incidence of:

a.       Hip dysplasia.

b.      Torn cruciate ligaments.

c.       Elbow dysplasia.

d.      All of the above.

Yes, all of the above are true. According to a study that investigated 1,500 Labradors, neutering before six months of age doubled the incidence of one or more of these joint diseases in both males and females.

7.  Castration prevents:

a.       Prostate gland infections (bacterial prostatitis).

b.      Benign prostatic hyperplasia (age related prostate gland enlargement).

c.       Testicular tumors.

d.      All of the above.

With conventional neutering, both testicles are removed. So, it’s a given that this eliminates the possibility of testicular tumors. Removal of the testicles also eliminates testosterone production and that, in turn, causes the prostate gland to shrink down to a teeny tiny size. Bacterial infections don’t occur in such small prostate glands. Additionally, without testosterone benign prostatic hyperplasia doesn’t occur.

8. Neutering at a young age:

a.       Does not impact adult conformation (body size, shape, and structure).

b.      Increases the likelihood of urinary incontinence in female dogs.

c.       Decreases the likelihood of developing hypothyroidism (inadequate thyroid hormone production) later in life.

d.      Prevents most undesirable behaviors.

Urinary incontinence is a common problem in middle aged and older female dogs. A review of several studies concluded that there is a link between spaying and the incidence of incontinence, particularly in dogs neutered at a young age.

Neutering can decrease some undesirable behaviors including dog on dog aggression, urine marking, mounting and roaming. However, there are many undesirable behaviors (fear induced aggression, resource guarding, territorial aggression, separation anxiety, noise phobias, decreased trainability, excessive barking) that are not reduced with neutering. In fact, the Vizsla study cited in question number 5 indicates that neutering exacerbates undesirable behaviors.

A study evaluating 3,206 dogs with hypothyroidism documented that neutering is associated with higher incidence of hypothyroidism, particularly in females.

Lastly, neutering does impact adult conformation as explained in question number 4 above.

9.  Neutering helps prevent:

a.       Mammary (breast) cancer.

b.      Prostate gland cancer.

c.       All types of aggression.

d.      All of the above.

Spaying decreases the incidence of breast cancer, depending on the age at which surgery is performed. A study performed in 1969 demonstrated that dogs spayed before their first estrus (heat cycle) have a 0.5% incidence of breast cancer. When spayed between their first and second estrus, the incidence increases to 8%. Dogs spayed after two or more estrus cycles have a 26% occurrence, and when dogs older than two and a half years of age are spayed, the incidence of mammary cancer increases to 40%. This is the only published study to have produced such hard and fast findings. Nonetheless, the study results are consistent with what is seen in clinical practice.

While castration does decrease the incidence of benign prostate gland diseases, it does not protect against prostate gland cancer. In fact, neutered dogs have a higher incidence of this disease than intact dogs.

See question 8 above regarding the impact of neutering on aggressive behaviors. behavior.

10.  Neutering should ideally be performed:

a.       Between four and six months of age.

b.      Before one year of age.

c.       After a female’s first heat cycle.

d.      If and when deemed appropriate based on the individual dog, its intended purpose, and living situation.

Based on all of the information presented above, I hope you understand why the answer to this question is “d”. The decision about if and when to neuter your dog should be based on careful assessment of the pros and cons of neutering in conjunction with your level of responsibility towards preventing unintended breeding.

Well, how did you do? Did any of this surprise you? Will this information change your thought process about neutering your own dogs in the future?

Best wishes,

Nancy Kay, DVM

Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Recipient, Leo K. Bustad Companion Animal Veterinarian of the Year Award
Recipient, American Animal Hospital Association Animal Welfare and Humane Ethics Award
Recipient, Dog Writers Association of America Award for Best Blog
Recipient, Eukanuba Canine Health Award
Recipient, AKC Club Publication Excellence Award
Become a Fan of Speaking for Spot on Facebook

Please visit http://www.speakingforspot.com to read excerpts from Speaking for Spot and Your Dog’s Best Health.   There you will also find “Advocacy Aids”- helpful health forms you can download and use for your own dog, and a collection of published articles on advocating for your pet’s health. Speaking for Spot and Your Dog’s Best Health are available at www.speakingforspot.com, Amazon.com, local bookstores, and your favorite online book seller.

Be Sociable, Share!

Leave a Reply

Your email address will not be published. Required fields are marked *