The effects of spaying and neutering dogs are variable. But are the outcomes acceptable from a health, behavior and welfare standpoint? What does the current research say? Earlier studies were used to justify surgical interventions, but those studies had methodological shortcomings and inadequate sample sizes. Politics have also confounded the public’s understanding since there has been a long standing dispute with the animal rights community over private ownership of domesticated animals of any type, and thus we have been told fantastical stories to justify the potential elimination of pets and livestock. Many studies have been hampered by very small sample sizes, and are often the results of surveys which can lack objectivity. The latest studies have been better constructed to help guide owners and veterinarians. This post isn’t medical advice, it is about animal welfare ethics. Ask your vet for their medical advice. Feel free to talk to me about my opinions on animal welfare. Let’s take a glance at the current thinking.
In 2013, UC Davis published the results of a study regarding the health effects of spaying or neutering Golden Retrievers. This breed was chosen to be a representative sample of a typical dog. The conditions being studied were: “hip dysplasia, cranial cruciate ligament tear, lymphosarcoma, hemangiosarcoma and mast cell tumor. The dogs were classified as intact (not neutered), neutered early (before 12 months age), or neutered late (at or after 12 months age).” What were the results? “The study revealed that, for all five diseases analyzed, the disease rates were significantly higher in both males and females that were neutered either early or late compared with intact (non-neutered) dogs. Specifically, early neutering was associated with an increase in the occurrence of hip dysplasia, cranial cruciate ligament tear and lymphosarcoma in males and of cranial cruciate ligament tear in females. Late neutering was associated with the subsequent occurrence of mast cell tumors and hemangiosarcoma in females.”
An updated study, published in 2020 (“Assisting Decision-Making on Age of Neutering for 35 Breeds of Dogs: Associated Joint Disorders, Cancers, and Urinary Incontinence” by Benjamin L. Hart, Lynette A. Hart, Abigail P. Thigpen, and Neil H. Willits) found similar results as follows: “Neutering (including spaying) of male and female dogs in the first year after birth has become routine in the U.S. and much of Europe, but recent research reveals that for some dog breeds, neutering may be associated with increased risks of debilitating joint disorders and some cancers, complicating pet owners’ decisions on neutering. The joint disorders include hip dysplasia, cranial cruciate ligament tear or rupture, and elbow dysplasia. The cancers include lymphoma, mast cell tumor, hemangiosarcoma, and osteosarcoma. In previous studies on the Golden Retriever, Labrador Retriever and German Shepherd Dog, neutering before a year of age was associated with increased risks of one or more joint disorders, 2–4 times that of intact dogs. The increase was particularly seen with dogs neutered by 6 months of age. In female Golden Retrievers, there was an increase in one or more of the cancers followed to about 2–4 times that of intact females with neutering at any age.”
A report published in 2018 (“Aggression toward Familiar People, Strangers, and Conspecifics in Gonadectomized and Intact Dogs” by Parvene Farhoody, Mallawaarachchi, Patrick M. Tarwater, James A. Serpell, Deborah L. Duffy, and Chris Zink6) related the following: “This large, comprehensive study of the relationships between gonadectomy and aggressive behavior in dogs demonstrates that when the many factors affecting aggressive behavior are considered, there is no evidence that gonadectomy at any age alters aggressive behavior toward familiar people or dogs, and there is only a minimal increase in aggression toward strangers. Given the increasing evidence of significant negative health effects of gonadectomy, there is an urgent need to systematically examine other means of preventing unwanted procreation, such as vasectomy and hysterectomy.” The most often cited study (Hopkins et al., 1976) was the result of a very small sample size. These latest results are better and should, in my opinion, replace the reliance on the old study. Furthermore, most dog trainers will tell you they have not seen significant changes in dog aggression after dogs were spayed or neutered, and that behavioral interventions were the solution to either better manage or stop the incidents of aggression.
Another paper indicated the following: (“Does Spaying and Neutering Affect Behavioral Disorders in Dogs?” World Small Animal Veterinary Association Congress Proceedings, 2017, Lisa Radosta, DVM, DACVB): “Duffy reported that in a survey of 1552 dog owners who were also members of pure bred dog breed clubs that owners of spayed dogs were significantly more likely to report aggression toward strangers, fear of people and sensitivity to touch. In addition, evidence was presented to support that spaying increases interdog aggression, but only in certain breeds. In another survey by the same author of 3593 dog owners who visited the author’s website to take the online survey, owners of spayed dogs were significantly more likely to complain of dog and owner directed fear and aggression; touch sensitivity and fear. Dogs who were spayed were calmer.”
A more disturbing find by Pavlov in his laboratory: dogs that were castrated were highly likely to break down and develop significant emotional disturbances, some of which never went away. The shock of strict confinement, the stresses of the lab, and the shock of castration wrecked these dogs. I think this should be a warning to all animal shelters that spay or neuter animals while in their facilities. It is my opinion many dogs are being doomed to eventual euthanasia because they don’t know the science and unsuspecting owners are getting emotionally and medically damaged dogs as a result. We shouldn’t be lying to people, saying they should fix their dogs so the shelters aren’t full, when we now know the significant risks. Shelters are full because the system is broken.
I was told for years that dogs were healthier and better behaved if they were spayed and neutered. Everyone said that. But, in my mind, I had this thought: if being intact was lethal, then we’d all be dead. Being intact would be anti-survival and species would die out. That doesn’t happen. My intuition has proven to be true. There are indications that spayed and neutered dogs might be less prone to some cancers later in life, but the data is limited.
Should you spay or neuter your dog? Well, that’s up to you. Balance what you learn from your vet with your personal values. But, I think you should be aware that some of the supposed benefits have been oversold for political reasons. I wouldn’t do it on a young dog. if you don’t want to create new puppies, then maybe we should be using the same procedures used on humans: vasectomy or tubal ligation. See if your veterinarian can recommend other options.