A new relationship with animals, nature and each other.

Health Concerns about Spay/Neuter

Spay/neuter is one of the bedrocks of the no-kill movement. Every year it saves millions of unwanted dogs and cats from being born. But veterinarians are always looking for better ways of preventing unwanted pregnancies. And in this guest post, Prof. Hal Herzog looks at new research that challenges conventional wisdom that desexing dogs is also good for their health.

By Hal Herzog, Ph.D.

In 1867, the streets of New York were awash with homeless dogs. The city council took action. Stray dogs were to be impounded and drowned en masse via a device dubbed “the canine bath tub.” The “tub” was an iron crate seven feet long, four feet high, and five feet across. Forty-eight dogs at a time were jammed into the heavy cage. It was then lifted up by a crane, swung over the East River and submerged. Ten minutes later, the cage was hauled to the surface, the carcasses removed, and the cage reloaded with another batch of strays. Dog catchers could kill 750 animals in a seven-hour shift.

The Good News: There Are Fewer Unwanted Pets

Today, “euthanasia” techniques are more humane. (See the discussion of “the blue needle” in Jessica Pierce’s wonderful new book on the aging and death of pets.) And the number of unwanted dogs and cats killed in animal “shelters” dropped from 24 million in 1970 to about 4 million in 2007. There are a couple of reasons for this dramatic decline. One is that animal protection organizations succeeded in convincing Americans that adopting a shelter dog is morally preferable to purchasing a purebred puppy. (This trend has devastated the American Kennel Club. AKC puppy registrations plummeted from one and a half million in 1992 to less than 600,000 in 2010.)

Some new research muddies the ethical waters on the spay/neuter issue.

An equally important reason for the decrease in unwanted pets is the success of the spay/neuter movement. Thanks to the efforts of animal protection organizations, most dogs and cats in the United States are now “neutered.” Indeed, responsible pet guardianship is now equated with having your companion animal’s testicles or ovaries removed, and in some communities it is illegal to allow a dog to reproduce without a special permit.

Given the benefits of having fewer homeless dogs and cats, it would seem that desexing our pets is a no-brainer. However, last summer at the meeting of the International Society for Anthrozoology, animal behaviorist/veterinarian Ben Hart told me about some research he was working on that muddies the ethical waters on the spay/neuter issue. Ben has a penchant for spinning my head around. This time, he swore me to secrecy until the results were published, which happened last week. Here is a copy of the article.

The Bad News: Neutering Can Be Bad for Your Pet’s Health

A research team from the University of California at Davis (including Ben and his wife, Lynette Hart) examined the records of 759 golden retrievers seen at the UC-Davis veterinary hospital between 2000 and 2009. (They focused on goldens because of the breed’s popularity and their propensity for cancer and bone and joint disorders.)

Here is a summary of the results. (Note that “early-neutered” animals were desexed before they were one year old.)

  • Hip dysplasia— twice as common in early-neutered males as intact males. No effect on females.
  • Knee ligament damage– higher incidence in early-neutered males and females.
  • Lymphatic cancer– three times more common in early neutered males than intact males. No effect in females.
  • Cancer of blood vessel walls– four times more common in late-neutered than intact females. No effect in males.
  • Mast cell tumors – significantly more common in late-neutered females. No effect in males.

In short, the researchers concluded that early and/or late neutering increased the risks of all five diseases in golden retrievers. Their study was restricted to one breed, but other studies have also reported deleterious consequences of desexing healthy dogs. For example, castrated elderly male dogs are at greater risk for canine dementia. And another recent study found that neutering increased aggression problems in female dogs.

“The negative health effects may well outweigh the positive effects.”

As you might expect, the relative health costs and benefits of routine neutering on the health of individual animals have become a topic of controversy. (For reviews see here and here.) For example, the American Veterinary Medical Association’s brochure on spay and neuter omits any mention of the negative effects of desexing pets. Yet several recent reviews of the impact of neutering on dogs concluded that the negative health effects may well outweigh the positive effects. Indeed, after reviewing dozens of research articles on desexing pets, a research team headed by Clare Palmer of Texas A and M wrote:

“Our overall conclusion is that routine neutering of companion animals, and notably male dogs, is not morally justified.”


The Moral Dilemma

No one wants to go back to the days when 24 million unwanted cats and dogs got the blue needle each year. But here is the ethical quandary: While neutering reduces suffering in general, it may well put your individual pet at greater risk of a serious disease such as cancer. It’s a classic conflict between what is best for the individual versus what is best for society.

It’s a classic conflict between what is best for the individual versus what is best for society.Is there an alternative to routine desexing of pets? Perhaps. While the American ideal of near universal neuter seems to be spreading, Europeans are less inclined to desex their pets. This is particularly true in Scandinavia. In Sweden, fewer than 7 percent of female dogs and even fewer males are neutered. Indeed, until 1988, it was illegal for Swedes to remove the reproductive organs of their dogs and cats unless medically indicated. Stine Christiansen, a Danish anthrozoologist and veterinarian, told me that when dogs are neutered in her country, it is nearly always for medical or behavioral reasons rather population control.

Christiansen adds, however, that there is no pet overpopulation problem in Denmark because people simply do not let their pets run loose. The same is true in Norway, where, with a few exceptions, it is presently illegal to desex healthy dogs.

I mentioned the UC Davis paper on golden retrievers to Jane Finneran, a highly regarded dog trainer. Jane was not keen on the idea that dog guardians who don’t let their animals run loose would do better to not neuter their pets.

“Far more puppies are killed in shelters from the ‘oops’ than any number of golden retrievers who will die from cancer!” she told me.

I expect Jane is right. But in light of the UC-Davis study and similar findings by other researchers on the health effects of neutering companion animals, I am now troubled by my unquestioning enthusiasm for plucking the gonads from every dog and cat in America.

P.S. Another Approach

A final note: When I first posted the above on my blog at Psychology Today, Ben sent me this e-mail offering a different approach:

Hal, a possible solution is vasectomy for male dogs and tubal ligation for females.

These operations are much less expensive and less traumatic for the dogs. The weird thing is we don’t teach these simple operations yet in vet schools, but shelter vets could learn it in an afternoon wet lab.

Hal Herzog is a psychologist at Western Carolina University whose research focuses on our attitudes towards and interactions with other species. His book Some We Love, Some We Hate, Some We Eat: Why It’s So Hard to Think Straight About Animals is published by HarperCollins.