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New Research That Raises Questions About Current Neutering Recommendations

Results from a hot-off-the-press study published by the Journal of the American Veterinary Medical Association, raise questions about traditional neutering recommendations within the United States where most veterinarians advise that dogs be neutered at a young age in order to induce sterility and eliminate behavioral issues before they have a chance to begin. This new information along with data from other recent studies are a prompt for all of us to reconsider current neutering dogma.

The title of the newest study is, “Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas.” The word “gonadectomized” is medical jargon for “neutered”. The research included 2,505 dogs and was supported by the Vizsla Club of America Welfare Foundation.

Effect of neutering on the incidence of cancer

Here is what the researchers learned about the prevalence of cancer as it relates to neutering:

Mast cell cancer: 3.5 times higher incidence in neutered male and female dogs, independent of age at the time of neutering.

Hemangiosarcoma: 9.0 times higher incidence in neutered females compared to nonneutered females, independent of age at the time spaying was performed. No difference in incidence of this disease was found for neutered versus nonneutered males.

Lymphoma (lymphosarcoma): 4.3 times higher incidence in neutered male and female dogs, independent of age at the time of neutering.

Other types of cancer: 5.0 times higher incidence in neutered male and female dogs. The younger a dog was at the time of neutering the younger the age of the dog at the time the cancer was diagnosed.

All cancers combined: 6.5 times higher incidence of cancer in neutered females compared to nonneutered females; 3.6 times higher incidence of cancer in neutered males compared to nonneutered males.

Effect of neutering on the incidence of behavioral issues

The research documented that dogs neutered at or before 6 months of age were at greater risk for developing a variety of behavioral issues including: separation anxiety, fear of noises, fear of gunfire, timidity, excitability, submissive urination, aggression, hyperactivity, and fear biting. Neutering after 6 months of age did not create increased risk. Fear of storms was the behavioral exception. Regardless of age at the time of neutering, neutered Vizslas were at greater risk for developing fear of storms than their nonneutered cohorts.

What does all this mean?

Interesting stuff, eh? From my perspective, I think this is a good wakeup call for anyone still clinging to the notion that all dogs not used for breeding purposes should be neutered at a young age. The recent studies that challenge traditional neutering recommendations seemingly raise more questions than they answer. All have studied large breed dogs (Rottweilers, Golden Retrievers, and now Vizslas). Do these results translate to small and medium sized dog breeds as well? Would similar studies within every breed produce differing results? Should males and females be spayed at a different ages? Are the effects of neutering on behavior breed-specific?

Clearly, there is much more research to be done before determining exactly how current neutering recommendations should be altered (pun intended). For now, what makes the most sense is one-on-one discussion between family veterinarians and their clients to determine how factors such as current knowledge about the effects of neutering, intended use of the dog, breed, temperament, and the way in which the dog will be housed and cared for influence the decision of whether or not to neuter and, if so, at what age.

An important disclaimer from this author: Please do not interpret what I have written to mean that I am opposed to neutering. Nothing could be further from the truth. From a pet overpopulation point of view, I am strongly in favor of neutering. Unplanned/unwanted litters of puppies are profoundly more problematic for me than any of the conclusions recent studies have reported.

Would recent research results influence your decision of whether or not to neuter your dog?

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
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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.