Longstanding practices around when to spay or neuter dogs are facing new scrutiny, as recent research reveals that early alteration may have lasting health consequences — particularly for larger breeds.
Veterinary scientists at the University of California, Davis have found compelling links between the timing of sterilization procedures and increased risks of joint disorders and certain cancers. Their studies emphasize that breed and size play a critical role in determining the healthiest course of action for each dog.
Larger Dogs at Higher Risk
Led by Drs. Benjamin and Lynette Hart, professors emeriti at UC Davis School of Veterinary Medicine, the research draws on data from more than 50,000 cases treated at the university’s veterinary teaching hospital. Their early work focused on Golden Retrievers, a breed beloved in American households and commonly used as service animals.
“The results were some of the most striking of any of the breeds,” said Dr. Lynette Hart.
The data revealed that Golden Retrievers neutered at any age were four times more likely to develop joint disorders such as hip dysplasia and cranial cruciate ligament tears. These issues stem from delayed closure of bone growth plates following hormone removal, which negatively affects skeletal development.
“When you delay the closure of the growth plate… it kind of throws off how the joint works,” explained Dr. Benjamin Hart.
The risks extended beyond the skeletal system. Female Golden Retrievers showed significantly higher rates of cancers — including lymphosarcoma, hemangiosarcoma, and mast cell tumors — whether they were spayed early or later in life.
“There’s no excellent solution for female Goldens,” said Dr. Lynette Hart. “They get hit from every side.”
Breed-Specific Recommendations
The Harts now advise that female Golden Retrievers remain intact when possible or undergo hormone-preserving procedures, such as ovary-sparing spays or tubal ligations. Though less common and more expensive, these surgeries aim to avoid the hormonal disruptions that may underlie long-term health problems.
Other large breeds — including Mastiffs, Bernese Mountain Dogs, Standard Poodles, and large mixed breeds — also benefit from delaying neutering until at least 24 months of age. Male Dobermans showed an elevated risk of cancer, while early-neutered female Dobermans and Sheepdogs were more likely to experience urinary incontinence.
In contrast, small breeds — such as Chihuahuas, Pugs, and Bulldogs — did not show significant negative health outcomes related to early neutering.
“The size of the dog makes a difference,” said Dr. Ben Hart.
Implications for Dog Owners and Vets
These findings are being shared widely by the American Kennel Club and are detailed in the Harts’ new book, The Perfect Puppy, a guide for both dog owners and veterinarians, particularly those working with service and working breeds like German Shepherds and Labradors.
While the researchers are not advocating against spaying or neutering altogether, they do urge a more individualized approach based on breed, size, and intended role of the dog.
“Hormone-saving procedures can be more costly,” Dr. Lynette Hart acknowledged, “but dog owners will move mountains to improve the health of their dog.”
Related topics:
Why Is My Dog Gaining Weight So Fast?
What’s the Best Feeding Schedule for Working Dogs?
When Is It Okay to Give My Dog Treats?
