An Update on the Health Effects of Spay/Neuter in Dogs

02/20/2019
Author: Sharon M. Albright, DVM, CCRT

Spaying or neutering a pet has been common practice in the United States for many years. It is estimated that over 80% of U.S. dogs are spayed or neutered (hereafter referred to as neutered) in an effort to control the pet population, decrease the risk of mammary and prostate cancer, and decrease unwanted behaviors such as aggression and roaming. Over the past 20 years, the scientific literature has shown that the decision if, and when, to neuter a dog is not so straightforward. The AKC Canine Health Foundation (CHF) and its donors have invested in research to explore the effects that neutering can have on dogs’ health. Evidence-based, breed-specific information is needed so that caregivers can make the best decisions for the long-term health of their dog(s).

Since 2010, Dr. Benjamin Hart and his team at the University of California, Davis have received three grants from CHF to examine the health implications of neutering:

  • 01488-A: Health Implications of Spay and Neuter: Golden Retriever and Labrador Retriever
  • 01840: Health Implications of Early Spay/Neuter on Canine Health
  • 02275: Disease Risks Associated with Spay and Neuter: A Breed-Specific, Gender-Specific Perspective

Retrospective examination of computerized hospital records from the Veterinary Medical Teaching Hospital at UC Davis over a period of 13-15 years has been conducted to explore the effects of neutering on disease risk. Data analysis is ongoing but results thus far demonstrate that the effects of neutering vary depending on exactly when a dog is neutered, whether the dog is male or female, and the breed or size of dog. Researchers have specifically evaluated the effect on clinical orthopedic disease (hip dysplasia, elbow dysplasia, and cranial cruciate ligament disease), neoplasia (lymphosarcoma, mast cell tumor, osteosarcoma, hemangiosarcoma, and mammary cancer), urinary incontinence, and pyometra. Golden Retrievers and Labrador Retrievers were studied first, followed by German Shepherd Dogs and numerous other breeds. This data will be used to build an open access database describing the health implications of neutering on 34 different dog breeds (Table 1).

Table 1 - Dog breeds studied for the health effects of spay/neuter with CHF funding

 Australian Cattle Dog  Collie  Pembroke Welsh Corgi
 Australian Shepherd  Dachshund  Pomeranian
 Beagle  Doberman Pinscher  Poodle (3 varieties)
 Bernese Mountain Dog  English Springer Spaniel  Pug
 Border Collie  German Shepherd Dog  Rottweiler
 Boston Terrier  Golden Retriever  Saint Bernard
 Boxer  Great Dane  Shetland Sheepdog
 Bulldog  Irish Wolfhound  Shih Tzu
 Cardigan Welsh Corgi  Labrador Retriever  West Highland White Terrier
 Cavalier King Charles Spaniel  Maltese  Yorkshire Terrier
 Chihuahua  Miniature Schnauzer  
 Cocker Spaniel  Parson Russell Terrier  


It is important to note that neutering appears to have a different effect on disease risk in different breeds. For example, in this data set, neutering increases the risk of having at least one of the studied orthopedic diseases in several breeds: that risk increases five times in a Golden Retriever neutered before six months of age, and doubles if the dog is a Labrador Retriever. In this study, the risk of lymphosarcoma, hemangiosarcoma, or mast cell tumor increased in neutered Golden Retrievers, but no such association was found in Labrador Retrievers or German Shepherd Dogs. In small breed dogs such as the Chihuahua, Yorkshire Terrier, and Dachshund, neutering appeared to have no significant effect on the risk for the orthopedic diseases or cancers studied.

With so much breed and gender-specific data, there is no one-size-fits-all solution for dog owners or veterinarians looking to make an informed decision on if or when to neuter a dog. Studies have examined different diseases, categorized different age ranges for neutering, and reported different statistics. The medical records used for the studies described above represent only a subset of dogs seen at a university teaching hospital and do not necessarily reflect the general dog population. It is also important to remember that correlation does not equal causation. Exposure to reproductive hormones is likely just one of several factors that contribute to the development of orthopedic disease and cancer; for example, obesity has been shown to influence both diseases. Finally, keeping the data in perspective is key. If neutering increases the risk of a common or fatal disease, it merits a more thorough consideration than its effect on a rare or treatable disease.

CHF acknowledges the importance of understanding neutering’s impact on the health of dogs. Breeders, owners, and veterinarians are encouraged to review the available literature, including the results of CHF-funded research at akcchf.org/research. The American Veterinary Medical Association also provides resources such as free webinars and a 2017 literature review. In summary, the decision whether to spay/neuter a dog must be made individually based on the pet’s age, breed, health status, intended use, temperament, and household environment and within a valid veterinarian-client-patient relationship. CHF will continue to fund quality research providing data that helps everyone make informed decisions to improve the health of dogs.

References:

  1. Torres de la Riva G, Hart BL, Farver TB, Oberbauer AM, Messam LLM, et al. (2013) Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers. PLoS ONE, 8(2): e55937. doi:10.1371/journal.pone.0055937
  2. Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2014). Long-term health effects of neutering dogs: comparison of Labrador Retrievers with Golden Retrievers. PLoS One, 9(7): e102241. doi:10.1371/journal.pone.0102241
  3. Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2016). Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence. Vet Med Sci, 2(3), 191-199. doi:10.1002/vms3.34


Learn more about Dr. Ben Hart’s CHF-sponsored research during the November 20, 2019 webinar “Addressing The Spay / Neuter Conundrum In Dogs: Some Breed-Specific and Body Size-Specific Guidelines.” Register at akcchf.org/vetvine.

 

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