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A study recently published in Frontiers in Veterinary Science has updated the ideal timeline for choosing to spay or neuter popular dog breeds in an effort to prevent the development of certain joint disorders or cancers. While the original 2013 study included data about 35 well-known dog breeds, the newest guidelines add in data for six* additional popular breeds: Siberian Husky, German Shorthaired Pointer, German Wirehaired Pointer, Rhodesian Ridgeback, Newfoundland, and Mastiff.

Findings Update Research on Role Hormones Play in Health

The findings published in Frontiers in Veterinary Science all stem from a study led 10 years ago by Drs. Benjamin and Lynette Hart, professors at UC Davis School of Veterinary Medicine. The pair set out to identify the ideal time to spay or neuter (or “alter”) Golden Retrievers, a breed well-known for both its popularity as a family pet and service work.

The data examined the health records of 759 male Goldens, and it found that a significant number of dogs neutered before 12 months old developed hip dysplasia as adults. The results indicated that early neutering had an adverse effect on young dogs’ growth plates and joints, essentially preventing their proper formation.

Looking back on the study, Dr. Lynette Hart reflects, “You know, it wasn’t a kind of work that people were interested in at the beginning. They didn’t even like it. It made life more complicated than neutering all the dogs at 4 or 6 weeks.”

Their research confirmed something Drs. Hart had long suspected: hormones play a much bigger role in dogs’ overall health and development than once realized. Following the study on Golden Retrievers, the two set out to identify ideal altering timelines for other breeds popular with families and dog enthusiasts. Their work set off a chain reaction of studies regarding hormone regulation and reproductive behavior in dogs, among other related topics.

Golden Retriever on an exam table having its heart checked by a vet.
vm via Getty Images

What Health Conditions Does Delayed Spay or Neuter Help Prevent?

A dog is constantly growing throughout puppyhood and adolescence. During these periods, not only do dogs get bigger, but their bones and joints fully form. If a dog is spayed or neutered too early, the lack of mature reproductive organs impacts hormone production, preventing connective tissues from developing properly.

“The hormones are involved in setting the time when the growth plate of the leg bones close,” Dr. Lynette Hart explains. “So, if you’re neutering, then the growth of the leg bones is shifted just a little bit. The leg gets a little longer, and then it just doesn’t match well in the joint. And that’s why you see an increase for some breeds in elbow dysplasia, hip dysplasia, or cranial cruciate tear.”

The lack of sex hormones from early altering in dogs can also increase the likelihood of cancers affecting bones, blood vessels, and lymph nodes. It can also cause mast cell tumors in some breeds.

“One surprise was that the first breed that we started with just by accident, the Golden, in a way is the most troubling. The results are the most troubling,” Dr. Lynette Hart explains. “Because neutering a female Golden at any age increases her risk of cancer. And she’s the only one like that.”

Siberian Husky wearing a cone on its head sitting outdoors.
AirQoo via Getty Images Plus

What Are the New Findings About Spaying or Neutering?

In addition to the original 35 breeds in the 2013 study, the new findings out of UC Davis’ research provide timelines for six additional breeds:

  • German Shorthaired and German Wirehaired Pointers, regardless of sex, shouldn’t be neutered or spayed before 12 months old
  • Siberian Husky males shouldn’t be neutered before 6 months old, while female Huskies shouldn’t be spayed before 12 months old
  • Rhodesian Ridgebacks, regardless of sex, shouldn’t be neutered or spayed before 6 months old
  • Mastiff males shouldn’t be neutered before 24 months old, while Mastiff females shouldn’t be spayed before 12 months old
  • Newfoundlands, regardless of sex, shouldn’t be spayed or neutered before 12 months old

There are other fascinating trends in the other breeds studied. For instance, research suggests that owners should refrain from spaying their female Shetland Sheepdogs while they’re under 24 months old – and not because of joint problems, but because of correlations to urinary incontinence. Interestingly, early spaying had no effect on the likelihood of joint disorders and cancer in female Pugs.

German Wirehaired Pointer getting attention.
©rodimovpavel -

Other Notable Findings Related to the Study

All of the current guidelines based on the new research are condensed into a quick-reference chart with spay-neuter timelines for the 41 breeds in the study. It’s a helpful reference resource for pinpointing the ideal time to alter a dog based on their sex and breed. Yet, it doesn’t delve into the many findings that took the Harts by surprise.

For example, Drs. Hart were surprised to learn that Labrador Retrievers and Golden Retrievers weren’t similarly affected by early spaying and neutering. Despite both being similarly sized dogs with several overlapping traits, Golden Retrievers were significantly more negatively affected by early altering.

“So that was the surprising thing. We just happened to hit on a breed where the breed is so vulnerable, and the joint disorders were increased so much by the early neutering,” says Dr. Lynette Hart.

Dr. Benjamin Hart adds that before being spayed, about 3% of female Golden Retrievers will experience one or more cancers in her lifetime. In canine cancer statistics, that’s pretty low. However, the likelihood skyrockets for male, intact Golden Retrievers. He explains, “It’s 11% [of males] that come up with the cancers. So males right off the bat are a bit more — quite bit more susceptible to some of the cancers. I think that’s the only breed where we’ve seen [the difference] quite like that.”

Table of timeline for neutering or spaying dog breeds
Frontiers in Veterinary Science

The Future of Delayed Spay-Neuter Research

Dr. Benjamin Hart remembers that their initial findings weren’t met with great enthusiasm.

“You know, there was a lot of pushback with the first paper on the Golden Retriever,” he says. “We chose that one because it’s a very popular breed, and we knew Golden Retrievers were a favorite for assistive animals … We knew one person that trained those animals that just gave up on the Golden because they came down with so many cancers. And joint disorders, too … We did that one and got an awful lot of pushback.”

But with time, research, and a deeper understanding of dog anatomy, that pushback wasn’t the end for this important work. The veterinary community has embraced the findings from the UC Davis School of Veterinary Medicine, and there are many more current studies looking to build on the Harts’ findings.

“The big lesson that we’ve learned, kind of the overriding one, is that people really care about their dogs, and they will do anything to find out how to take better care of them and avoid making them at greater risk for these problems,” Dr. Lynette Hart says. “It tells you the magnitude of how much people care about their dogs.”

How to Manage Life With an Intact Dog Responsibly

While the research supports important health benefits of delaying (or opting out of) spaying or neutering these breeds, anyone who lives with an intact (ie, not spayed or not neutered) dog must be vigilant about responsible management of that dog to prevent any unplanned matings or litters. Simple behaviors like always leashing your intact dog when in public, or safely and securely containing your intact dog when they’re unsupervised are essential. If your intact dog has access to your yard, be sure they’re always under supervision or completely contained and inaccessible to other dogs. Intact male dogs can be more likely to want to roam and try to leave their yards, and an intact female unsupervised in your yard can be an irresistible enticement to one of those roaming males.

You might consider using a belly band for male dogs or “bloomers” for females if marking behaviors or signs of estrus (being “in heat“) become challenging. If you have access to a reproductive veterinarian or veterinary teaching hospital, you might ask about hormone-preserving sterilization options for your dog—like canine vasectomy or ovary-sparing spays—if you eventually choose to alter your dog.

Vigilance, safety, secure containment, and supervision are essential, and in reality, they’re all already key to responsible ownership of any dog, intact or not.

*Editor’s Note: The study refers to “40” breeds in total as it groups German Shorthaired Pointers and German Wirehaired Pointers together. These are distinct AKC-recognized dog breeds, and so our math on the number of breeds in the study nets out at 41.

Related article: Why Do Male Dogs Lift Legs and Females Squat to Pee?
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