UC Davis study compares long-term health effects of neutering on golden retrievers, Labradors
In 2013, the UC Davis School of Veterinary Medicine published a study revealing that neutered golden retrievers are seemingly at a higher risk of joint disorders and cancers compared to sexually intact dogs of the same breed.
The university has now followed that research effort up with a study comparing the long-term health effects of neutering in golden retrievers and Labrador retrievers.
According to Benjamin Hart, DVM, Ph.D., lead investigator and professor emeritus at the veterinary school, the new study found that neutering impacts each breed's health differently.
"We found in both breeds that neutering before the age of 6 months, which is common practice in the United States, significantly increased the occurrence of joint disorders - especially in the golden retrievers," Hart said. "The data, however, showed that the incidence rates of both joint disorders and cancers at various neuter ages were much more pronounced in golden retrievers than in the Labrador retrievers."
To obtain their data for the study, researchers reviewed health records from the UC Davis School of Veterinary Medicine spanning a 13-year period. The records included 1,015 golden retrievers and 1,500 Labrador retrievers, and featured neutered and non-neutered male and female Labrador retrievers and golden retrievers all between 1 and 8 years of age. Researchers made sure to record whether individual dogs were neutered before 6 months, between 6 and 11 months, between 12 and 24 months, or between 2 and 9 years of age, the university said.
The research team used the health records to compare incidences of three cancers in the two breeds: lymphosarcoma, hemangiosarcoma, and mast cell tumor. They also gauged the incidence of three joint disorders in each breed: hip dysplasia, cranial cruciate ligament tear, and elbow dysplasia.
Joint disorders more common in golden retrievers neutered before 6 months
According to researchers, sexually intact dogs of both breeds and sexes had a 5-percent chance of at least one joint disorder. That rate doubled when Labrador retrievers are neutered before 6 months, and multiplied by four to five times for golden retrievers neutered before 6 months.
Male golden retrievers were more prone to hip dysplasia and cranial cruciate ligament tear, while Labrador retriever males had an increased risk of cranial cruciate ligament tear and elbow dysplasia, researchers said.
Female golden retrievers at elevated cancer risk after neutering
The study found that female golden retrievers were impacted most by neutering when it comes to cancer. In female goldens, neutering at any point after 6 months of age raised their risk of one or more cancers to three to four times that of non-neutered females, researchers said. Neutering in female Labrador retrievers only slightly raised the cancer rate.
"The striking effect of neutering in female golden retrievers, compared to male and female Labradors and male goldens, suggests that in female goldens the sex hormones have a protective effect against cancers throughout most of the dog's life," Hart said.
Neutering studies eliciting mixed reactions
The effect of the UC Davis studies on neutering practices in the United States remains to be seen, as neutering has become a widely accepted method of reducing pet overpopulation and mitigating unwanted pet behaviors.
In a 2013 JAVMA News article, Hart acknowledged that the university's 2013 study had provoked a mixed reaction among the veterinary community and animal welfare organizations, but that resistance to the study findings was often balanced by positive reactions.
“Understandably, we see plenty of push back, along with lots of compliments like ‘thank goodness someone is finally doing something about the issue, especially the very early neutering’,” Hart said.
In the same article, Philip A. Bushby, DVM, DACVS, professor of humane ethics and animal welfare at the Mississippi State University College of Veterinary Medicine, said the study had made waves and even caused some veterinarians to reconsider the current neutering approach. At the same time, he cautioned that the subject needs much more exploration before any major changes are considered.
“These data are real, the issue is there, but the numbers are real small,” Bushby said. “We know that spay-neuter increases the incidences of some tumors and some medical conditions. We know that. We know that spay-neuter decreases the incidences of some tumors and some medical conditions. We know that. But before we, as a profession, make any major decision about spay-neuter, we should look at more numbers, and before we try to extrapolate these findings across all dogs, we should look at populations in general, not just one breed.”
Looking forward, Hart said the studies provide useful information for researchers in veterinary and human medicine. He also noted that breeders and pet owners could take the findings into consideration when making neutering decisions about their dogs.