Luvk9s Dog Training

Spay/Neuter Dogma


Most of us have lived by the “neutering dogma” that suggests spaying and neutering should be performed by age 6 months, and in females, certainly before the first heat.
While this is still the rule of thumb for rescue organizations whose goal is to control the homeless pet population, recent research is offering some interesting statistics that provide canine aficionados with some food for thought.


What follows are some studies presented in a webinar by Dr. Nancy Kay called “Changing perspectives about Canine Spay and Neuter.”  Click on the title for more detailed information.

Endogenous Gonadal Hormone Exposure and Bone Sarcoma Risk

Dawn M.  Cooley, et al 

Cancer Epidemiology, Biomarkers & Prevention - November 2002


The objective of this study was to determine the relationship between the time of spay/neuter and the development of sarcoma; 683 Rottweiler owners participated in the study.

  • Bone sarcoma was diagnosed in 12.6% of dogs.
  • Males and females neutered before 1 year of age had 3-4 times greater incidence than intact dogs.
  • The earlier the time of neutering, the greater the risk for bone sarcoma.

The conclusion of this study is that delaying spaying and neutering protects Rottweilers from developing bone sarcoma.

Neutering Dogs:  Effects on Joint Disorders and Cancers in Golden Retrievers
Gretel Torres de la Riva, et al, 
PLoS One – February 2013

The objective of this study was to review the medical records of 759 golden retrievers between the ages of 1 – 8 to determine if early neutering (before 1 year of age) versus late neutering (after 1 year of age) had any effect on the incidence of hip dysplasia, cruciate ligament tear, lymphosarcoma, hemangiosarcoma and mast cell tumors.


  • Early-neutered males: 9.6% incidence
  • Late-neutered males: 0% incidence
  • Intact males: 3.5% incidence
  • Female dogs: no statistical differences


  • Intact females: 1.6% incidence
  • Early-neutered females: 1.8% incidence
  • Late-neutered females: 7.4% incidence
  • Intact versus neutered males: no statistical differences


Mast Cell Tumors

  • Intact females: 0% incidence
  • Early-neutered females: 2.3% incidence
  • Late-neutered females: 5.7% incidence
  • Intact versus neutered males: no significant differences


For all the diseases that were analyzed, incidence of the disease was significantly influenced by neutering.  Age and gender also played a role. Orthopedic issues may be related to alteration of growth plate closure caused by neutering.

Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers
Benjamin L. Hart, et al
Plos One- July 2014

This study fascinated me, as I expected the results to be similar for golden and Labrador retrievers – but they weren’t!

Hospital records of 1,015 golden retrievers and 1,500 Labrador retrievers, between the ages of 1 – 8 years were studied to analyze the occurrence of hip dysplasia, cruciate ligament disease, elbow dysplasia, lymphosarcoma, hemangiosarcoma and mast cell tumors.

The study concluded that:

  • Early neuter increases incidence of joint diseases studied (though more in goldens than in labs.)
  • Spayed female goldens had an increased susceptibility to development of cancer; no such effect was observed with labs.
  • Early neutering increased the incidence of lymphosarcoma in goldens but not labs.

Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas

Christine M. Zink, et al
JAVMA – February 2014


In this study, 2,505 Vizsla owners participated in a survey gathering information on neutering status and age at diagnosis of various cancers and behavior disorders.

  • Mast cell cancer, 3.5 times higher incidence in neutered males and females independent of age at time of neutering.
  • Hemangiosarcoma, 9 times higher incidence in males neutered after 12 months of ag and in spayed females independent of age at time of spay.
  • Lymphosarcoma, 4.3 times higher incidence in neutered males and females independent of age at time of neutering

Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence 
Benjamin Hart, et al

Veterinary Medicine & Science – May 2016

This study used the hospital records of 1,170 dogs with a mix of neutered and intact males and females looking for various types of cancer, joint disorders, and urinary incontinence.

Conclusions of the study:

  • Incidence of cruciate ligament disease is increased in neutered GSD.
  • Incidence of mammary cancer is increased in intact GSD (but neutering before 6 months protects the dog from mammary cancer.)
  • Incidence of urinary incontinence increased in female GSD.

Reproductive Capability is Associated with Lifespan and Cause of Death in Companion Dogs
Jessica M. Hoffman, et al
PLoS One – April 2013

This study fascinated me in that it included 185 different breeds of dogs and the outcome of the study was completely opposite of some of the previously mentioned breed specific studies.

This study looked at the age and cause of death in 70,574 dogs where 43.6% were intact and 56.4% were neutered. (Age at the time of neutering was not accessed.)
Results of the study:

  • Mean age of death of intact dogs – 7.9 years
  • Mean age of death of neutered dogs – 9.4 years
  • Neutering increased life expectancy of males by 13.8%
  • Neutering increased life expectance in females by 26.3%
  • Incidence of some cancers significantly increased in neutered dogs (osteosarcoma, lymphosarcoma, mast cell tumor)
  • But mammary cancer significantly decreased in neutered dogs
  • Intact dogs were more likely to die from infectious diseases, trauma, degenerative disease, vascular disease
  • Neutered dogs were more likely to die from cancer, immune mediated disease.

The conclusion of this study was that neutered dogs live longer than intact dogs.

Impact of neutering (male and female) on behavior

The speaker also expressed these thoughts regarding the impact of neutering on behavior.

Urine marking:  Neutering can reduce the incidence of urine marking by 60%.
Mounting: Neutering can decrease mounting behavior by 50 – 60%.
Roaming: There is up to a 90% decrease in roaming in neutered dogs.

Aggression:  Effects of neutering male dogs.

  • Cannot be expected to reduce aggressive behavior in all dogs.
  • Does not consistently and completely eliminate aggressive behaviors.
  • The age at which neutering is performed does not have value in predicting magnitude of change in behavior.
  • Neutering should be considered as an adjunct to other behavior practices.
  • Neutering males doesn’t render them useless for protection/guarding (not much impact on aggression towards people.)

Aggression:  Effect of Neutering on Female Dogs

  • Spaying shortly following estrus (first several weeks) can induce behavior changes caused by sudden drop in progesterone.
  • Spaying can increase aggression towards guardians, particularly if performed prior to 12 months of age.



As Dr. Kay stated in her webinar, there is no “one size fits all” response as to whether dogs should be neutered, or if they are neutered, at what age.

Factors to keep in mind:

Human factor

  • How involved will the owner be in the dog’s care?
  • Will the dog receive training?
  • Will the owner of an unneutered dog be able to never allow the dog to roam?
  • Does the owner understand what is involved in having a female in heat?

Intended use of the dog.

  • Show dogs are not neutered.
  • Dogs that will be used in athletics (dock diving, agility, etc.) might need to be neutered later after growth plates close.
  • Dogs that are going to be your typical companion dog might be best off neutered based on the results of the companion dog study mentioned above.

Owners personal history.

  • An owner who has had a female golden retriever that passed away from cancer might rethink whether to automatically neuter their next golden at 6 months.

In conclusion
We don’t have data for all breeds. But there is compelling evidence for rethinking automatic neutering at 6 months for some breeds.

Other breeds or mixed breeds are an entirely different issue. Current data (see Reproductive Capability is Associated with Lifespan and Cause of Death in Companion Dogs) shows that neutered pets live longer than unneutered pets.

Neutering can impact behavior (urine marking, mounting, etc.)
Whether or not to neuter (or at what age) is on longer a simple question to answer. Remain open-minded, do your research, be a responsible dog owner and do what is best for your specific situation.