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Neutering And Spaying Dogs, What Are The Risks?

Does Neutering And Spaying Dogs Decrease The Risk Of Cancer?

neutering a male dogI was recently asked the question if neutering your male dog at a later age in life would reduce the risk of  of prostate cancer.  Most veterinarians were taught in vet school that neutering a dog is beneficial to their health.  However, quite the opposite is true.  I firmly believe the push to spay and neuter dogs was misinformation embedded in our brains by veterinarians and public service announcements to simply control the pet population.  Controlling the pet population is very important as there are so many irresponsible people who refuse or are unable to control their dogs activities outside the home.  However, spaying and neutering is not the answer.  This practice was a logical attempt to solve the problem of overpopulation, but the dog’s overall health did not equate into the practice of spaying and neutering.  The reason for this is simple, there were no funded studies done on how this practice would effect the health of dogs.  In 2007 however, there were studies done and the results will astonish you.

The results of this study were published in the Prostate Journal on August 1st 2007 Volume 67, Issue 11, Pages 1143-1254.  Scientific data was gathered from hundreds of North American Veterinary Teaching Hospitals on intact male dogs that had been neutered (testicles surgically removed, or castrated), to evaluate the prevailing trend that had been discovered in many older articles that neutering increased prostate cancer.  The study found that castration of intact male dogs increases the risk of malignant prostate cancer by eight times for some prostate cancers (prostate adenocarcinoma).  The study also found Castration of dogs increases the most common type of bladder cancer (transitional cell carcinoma) by about four times.  This study is huge and should have been an eye opener for veterinarians, but most have chosen to ignore this study. One can only guess that this information if followed, would only cut into the vets profit margins.  I thought veterinarians were supposed to have the best interests of the animals they medically treat in mind.

There was also a more recent study done titled “Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas.”  The Vizslas  study was conducted by a team of researchers with support from the Vizsla Club of America Welfare Foundation. It was published in the February 1, 2014 issue of the Journal of the American Veterinary Medical Association.

There were 2,506 dogs involved in the Vizsla study.  The reported results are as follows:

  • Dogs neutered or spayed at any age were at significantly increased risk for developing mast cell cancer, lymphoma, all other cancers, all cancers combined, and fear of storms, compared with intact dogs.
  • Females spayed at 12 months or younger, and both genders neutered or spayed at over 12 months had significantly increased odds of developing hemangiosarcoma, compared with intact dogs.
  • Dogs of both genders neutered or spayed at 6 months or younger had significantly increased odds of developing a behavioral disorder, including separation anxiety, noise phobia, timidity, excitability, submissive urination, aggression, hyperactivity, and/or fear biting. When it came to thunderstorm phobia, all neutered or spayed Vizslas were at greater risk than intact Vizslas, regardless of age at neutering.
  • The younger the age at neutering, the earlier the age at diagnosis with mast cell cancer, cancers other than mast cell, hemangiosarcoma, lymphoma, all cancers combined, a behavioral disorder, or fear of storms.
  • Compared to intact dogs, neutered and spayed dogs had a 3.5 times higher risk of developing mast cell cancer, regardless of what age they were neutered.
  • Spayed females had nine times higher incidence of hemangiosarcoma compared to intact females, regardless of when spaying was performed, however, no difference in incidence of this type of cancer was found for neutered vs. intact males.
  • Neutered and spayed dogs had 4.3 times higher incidence of lymphoma (lymphosarcoma), regardless of age at time of neutering.
  • Neutered and spayed dogs had five times higher incidence of other types of cancer, regardless of age of neutering.
  • Spayed females had 6.5 times higher incidence of all cancers combined compared to intact females, and neutered males had 3.6 times higher incidence than intact males.

I would conclude from these studies that it would be unwise to spay bitches or neuter dogs at any age.  I would also conclude that studies need to be done on safe way to sterilize dogs that does not impact their health with high incidents of cancer.

Neutering And Spaying Dogs, What Are The Risks? was last modified: by


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  • Carol coy
    · Reply

    This really opened my eyes. For the past few years my vet has been telling me my two older miniature schnauzers need to b neutered. He explained it’s because this needs to be done if not higher percentage of prostate cancer and other types of cancer. Dennis thank you for explaining to me with the proof it’s not necessary to neuter my dogs. Not neutering will actually help prevent cancer. I like those odds much better then what the Vet told me. You explained it in a way I understand it. I feel comfortable with my decision not to neuter my dogs. Thank you much Dennis. Carol

  • Gloria Janes
    · Reply

    I do agree with this article. I feel dogs are healthier intact. I feel they are more active and much healthier. Would love to hear what other breeders have to say about which has the better health, spayed/neutered or intact dogs. How do you handle the spay/neuter on your puppies per your sale contract? Do you require it? What age do you recommend? I have heard 2-1/2 years now is the youngest dogs should be spayed/neutered. Do you agree with this older age?

  • Dave Bonar
    · Reply

    Thanks for sharing this information. I have always been told that it was healthier for dogs to be fixed. I feel much better after reading this as our vet puts us on a guilt trip over not neutering.

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