The growing debate over spaying and neutering dogs

The owner of Astro, an 8-year-old golden retriever in Colorado, decided not to neuter him for health reasons. (Courtesy of Valerie Robson)

By Karin Brulliard, The Washington Post

Beneath the fluffy backsides of Valerie Robson’s two male golden retrievers is an unusual sight: intact anatomy. Neither dog is neutered. 

This presents occasional challenges. Astro and Rumble are barred from most doggy day-cares, and many boarding kennels won’t take them. But although Robson has no intention of breeding the dogs, she says she has no regrets. Research that suggests neutering could be linked to cancers and joint disorders persuaded her that skipping sterilization was best for her pets. 

“Sometimes people notice,” said Robson, a county government employee in Conifer, Colo. “I just explain that we chose to do this for health and wellness, and he’s a good boy, and it’s never been an issue.”

“Intact” dogs were the norm for a long time, and a litter of puppies was often part of the deal. But in the 1970s, when overflowing animal shelters were euthanizing millions of homeless dogs annually, spaying and neutering puppies — procedures that involve removing ovaries or testicles — became the dogma in the United States. 

It still is: Surveys indicate a large majority of pet dogs are fixed, and 31 states and the District require that pets adopted from shelters or rescues be sterilized. The surgeries simplify pet ownership by preventing females from going into heat and, some believe, by improving dog behavior, though experts say that is not clearly supported by research. 

But the common wisdom has been complicated in recent years amid widening evidence connecting spaying and neutering to health problems in dogs. The findings are stronger for certain breeds and large dogs, and age of neutering plays a role. But the research is causing some owners and veterinarians to question the long-held tenet that fixing puppies — or fixing, period — is a necessary part of responsible pet ownership. 

“We owe it to our dogs to have a much larger conversation about spay and neuter,” said Missy Simpson, a veterinary epidemiologist with the Morris Animal Foundation, a charity that funds animal health research. “It’s nuanced, and there isn’t a great one-size-fits-all recommendation for every dog.”

Simpson was lead author of a recent paper on about 2,800 golden retrievers enrolled in a lifetime study, which found that those spayed or neutered were more likely to be overweight or obese. The study also found that dogs fixed before they were 6 months old had much higher rates of orthopedic injuries, and that keeping dogs lean didn’t prevent those injuries. 

The research has sparked controversy in the veterinary and shelter worlds, in part because widespread spaying and neutering are credited with helping fuel a dramatic decline in euthanasia. The American Society for the Prevention of Cruelty to Animals, which says about 670,000 dogs are killed in shelters each year, supports “early-age” sterilization. 

“The question on a bigger level is to what extent are we sacrificing some bits of welfare for an individual animal for the welfare of the species?” said Stephen L. Zawistowski, science adviser emeritus at the ASPCA. “The fact that we can actually have the conversation is a sign that we’ve made such enormous progress.” 

‘It is complicated’

Spaying and neutering do have some clear health benefits for dogs. Testicular and ovarian cancers are moot, and there’s evidence that spaying lowers the risk of mammary cancer and uterine infections. Fixed dogs also live longer on average. 

But researchers say the reproductive hormones controlled by the removed sex organs have important systemic roles. They influence muscle mass and tendon and ligament strength, and they tell bones when to stop growing. “Without those hormones, your body might just not be as robust,” Simpson said. 

Bailey, an unneutered golden retriever, sits upright on the lap of his owner, Sherri Wilson. Madison, below him, died last year. (Courtesy of Sherri Wilson)

The recent debate over spaying and neutering flared in 2013, when a study from the University of California at Davis reported higher rates of hip dysplasia, cranial cruciate ligament tears and certain cancers among desexed golden retrievers — especially those neutered early, defined as before 1 year of age. The paper caused “quite a bit of controversy” among critics who “accused us of, you know, driving overpopulation of animals,” said author Benjamin Hart, a professor emeritus at Davis’s vet school. 

Hart and his colleagues later found higher rates of joint disorders, but not cancers, among Labrador retrievers and German shepherds that were neutered early. Their latest study, which is not yet published, examined 35 breeds and mutts and detected no associations between desexing and cancers or joint disorders in small dogs. But it found much greater rates of joint disorders among nearly all large dogs sterilized early, Hart said. 

“Dogs vary tremendously in their physiology, their anatomy. It’s not surprising they would vary in these other things,” Hart said. “It is complicated. That’s why people need to talk it over with their veterinarian.”