Should you neuter your dog to lower long-term health risks? A comprehensive study in Frontiers in Veterinary Science provides breed-specific insights from experts at the University of California, Davis.
Neutering male and female dogs before their first birthday is a common practice. However, certain breeds face heightened risks of diseases or disorders if neutered before six months. Previous research focused on limited breeds, but UC Davis researchers expanded analysis to 35 breeds, revealing significant variations by breed.
The team reviewed 15 years of records from thousands of dogs treated at the UC Davis Veterinary Medical Teaching Hospital. They examined whether neutering timing influences a breed's risk for cancer or joint disorders.
Joint issues studied included hip dysplasia, cranial cruciate ligament tears, and elbow dysplasia. Cancers analyzed were lymphoma, hemangiosarcoma, mast cell tumors, and osteosarcoma. Researchers also assessed sex differences.
Key takeaway: No universal rule applies.
"There is no 'one size fits all' when it comes to health risks and neutering age," says lead author Benjamin Hart, DVM. Some breeds develop joint issues but not cancer, or vice versa; others show no increased risks."
Joint disorder risks correlate with body size: Smaller breeds face fewer issues, while most large breeds are vulnerable, per co-author Lynette Hart, PhD. Exceptions: Great Danes and Irish Wolfhounds showed no elevated risks regardless of neutering age.
Cancer rates in small dogs remained low post-neutering, except in Boston Terriers and Shih Tzus, where risks rose. Sex matters too: Female Boston Terriers spayed at six months showed no cancer increase, but males neutered before one year did.
Large neutered dogs had higher cancer incidences overall.
Among 220 intact males, 203 neutered males, 128 intact females, and 210 spayed females, cancer rates were 17% (intact males) and 11% (intact females). Neutering males before age two raised risk by 32%; spaying females increased it by 20%.
Researchers recommend delaying neutering until at least age two for both sexes.
In 318 intact males, 365 neutered males, 190 intact females, and 374 spayed females, joint disorders affected 5% of intact males and 4% of intact females.
Males neutered before 6 months: 25% risk; 6-12 months: 11%. Females spayed before 6 months: 18% higher risk.
Cancer: 15% (intact males), 5% (intact females). Neutered males before 6 months: 19%; females before 6 months: 11%; 6-12 months: 17%.
Advice: Neuter males after one year; avoid spaying females if focusing on these risks.
To guide owners, researchers created breed-specific charts ("Beyond" indicates recommended delay).
While neutering helps curb pet overpopulation, this study urges owners to prioritize health. "Decisions should come from owners and vets, not societal pressure," Hart notes. This shifts paradigms for the most common veterinary procedure."
