How Does Spaying or Neutering Affect Large-Breed Dogs?

A 2019 study from the Morris Animal Foundation Golden Retriever Lifetime Study, published in PLOS ONE, reveals that the timing of spaying or neutering can have lasting effects on a dog’s health—especially for large-breed dogs.

For decades, pet parents have heard that spaying or neutering is simply part of being a responsible owner. And while these surgeries still play an important role in preventing overpopulation and certain diseases, new research shows it’s worth taking a closer look at when to schedule the procedure.

“Our study results give dog owners and veterinarians new information to consider when deciding when to spay or neuter their dog, especially when thinking about their long-term health,” said Dr. Missy Simpson, epidemiologist and lead author of the study.

What the Study Found

The study followed more than 3,000 golden retrievers from across the United States for six years. About half were spayed or neutered, while the other half remained intact. Researchers tracked their health, weight, and injury history throughout the study.

Key findings include:

• Dogs that were spayed or neutered were 50% to 100% more likely to become overweight or obese than intact dogs.

• This increased risk remained the same no matter when the surgery was performed—whether at 6 months or 6 years old.

• However, dogs that were spayed or neutered before 6 months of age were at a 300% greater risk of developing nontraumatic orthopedic injuries, such as cruciate ligament tears.

In other words, while sterilization at any age may increase the risk of weight gain, early-age surgery (before 6 months) appears to dramatically raise the chance of joint injuries, especially in larger dogs still developing their bones and muscles.

Why This Matters for Large-Breed Dogs

In the general canine population, up to half of all large-breed dogs are already overweight or obese, and around 2% experience non-traumatic orthopedic injuries. Adding an increased risk from early spay or neuter procedures could make these problems even more common.

“Different owners have different concerns for their dogs, and the decision to spay or neuter your dog is a very complex one,” explained Dr. Janet Patterson-Kane, Chief Scientific Officer at Morris Animal Foundation. “It’s a balance in managing the risks of neutering or not neutering for owners committed to their dog’s health.”

At the Drake Dog Cancer Foundation, we often remind pet parents that hormones play a crucial role in growth, bone density, metabolism, and even immune regulation. Removing them too early may influence how your dog develops both physically and metabolically.

What This Means for You and Your Dog

If you’re the parent of a large- or giant-breed dog, the timing of spaying or neutering deserves a thoughtful conversation with your veterinarian. Here are some key takeaways to guide that decision:

• Wait until full maturity when possible. For many large breeds, this means closer to 12–18 months old, when bone plates have closed and the body has finished developing.

• Maintain a healthy weight. Dogs that are spayed or neutered are more prone to weight gain. Regular exercise and a whole-food, portion-controlled diet can make a big difference.

• Watch for joint health. Provide joint-supportive nutrition, maintain proper muscle tone, and avoid high-impact activity in young growing dogs.

There is no one-size-fits-all answer. Every dog’s situation—breed, size, temperament, environment, and health background—should guide the decision. The goal is to protect your dog’s long-term wellness while still honoring your values as a responsible pet parent.

About the Study

The Morris Animal Foundation Golden Retriever Lifetime Study is the most comprehensive canine health study ever conducted. Since its launch in 2012, it has followed over 3,000 golden retrievers across the U.S., collecting yearly health data and biological samples to uncover the genetic, nutritional, environmental, and lifestyle factors that influence cancer and other diseases.

The study’s findings don’t just help golden retrievers; they shape what we know about canine health in all breeds.

Major supporters include:

• The Mark and Bette Morris Family Foundation

• Petco Foundation

• Blue Buffalo Company

• Mars Veterinary Inc.

• ANTECH Diagnostics and Imaging

• VCA Inc.

• Zoetis

• Golden Retriever Foundation

• Hadley and Marion Stewart Foundation

Timing Has Been Shown to Affect Health

Spaying and neutering remain valuable tools in responsible pet care, but like many decisions in canine health, timing and individualization matter.

The more we understand about how these procedures affect long-term wellness, the better equipped we are to make decisions that support both quality and longevity of life for our dogs.

At the Drake Dog Cancer Foundation, we encourage every pet parent to make informed, compassionate choices—guided by science, love, and the unique needs of your furry family member.

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