What Age Should Dogs Be Spayed/Neutered to Avoid Increased Health Risks?

New research adds more dog breeds to the list of those for which there are guidelines on when to spay or neuter them based on the health risks.

Female Golden Retrievers, like the one pictured on a lawn, have health risks if spayed, according to this research
Photo: Victoria Rak/Shutterstock


By Zazie Todd PhD

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In North America, it’s common to spay female dogs by removing the ovaries and uterus, and to neuter male dogs by castrating them, but there are concerns about health risks if this is done too early. New research builds on previous work on 35 breeds and analyzes the risks of joint issues and cancer for an additional five breeds (all large ones). 

The results mean there are now guidelines for the earliest age at which 40 different breeds of dogs should be spayed or neutered in order to avoid health risks. The research was conducted by a team of researchers at the University of California, Davis and published in Frontiers in Veterinary Science.

Previous research shows that in some breeds, early spay/neuter leads to an increased risk of several joint disorders: hip dysplasia, elbow dysplasia, and tears of the cranial cruciate ligament in the knee. As well, for some breeds there is an increased risk of certain cancers such as mast cell tumour, lymphosarcoma, hemangiosarcoma, and osteosarcoma. 

The current study looked at these disorders, as well as mammary cancer and pyometra in female dogs, and urinary incontinence in both male and female dogs.

The five large breeds that were included in this study are the German Wirehaired and Shorthaired Pointer, Mastiff, Newfoundland, Rhodesian Ridgeback, and Siberian Husky. Records from a teaching veterinary hospital were used to assess the risks. There were at least 200 dogs of each of these breeds, meaning there was enough information on which the scientists could base recommendations.

The data was used to develop guidelines for these breeds. Added together with the other breeds that were previously studied, the guidelines for 40 dog breeds are shown in the table below which is reproduced from the open access paper under a CC-BY license.

The recommended age of spay/neuter for 40 breeds of dog according to the scientific research
Reproduced from Frontiers in Veterinary Science under a Creative Commons license

According to the scientists, spaying is not recommended at all for female Golden Retrievers, and neutering is not recommended at all for male Doberman Pinschers. For the other breeds studied, the earliest age at which spay/neuter is recommended is given.

Many dogs are spayed or neutered at around 6 months because this is an age that helps with population control. The breeds where this is recommended at no earlier than 6 months for both male and female dogs include Australian Cattle Dog, Australian Shepherd, Bulldog, Cavalier King Charles Spaniel, Chihuahua, Corgi, Jack Russell Terrier, Maltese, Toy Poodle, Rhodesian Ridgeback, Saint Bernard, and the West Highland White Terrier. 

Breeds where it is recommended to wait until at least 24 months, according to the scientists, include the Boxer, German Shepherd, female Cocker Spaniel (but for males, from 6 months with this breed), female Doberman Pinscher, male Irish Wolfhound (females from 6 months), male Mastiff (females from 12 months), male Standard Poodle (females from 6 months), and female Shih Tzu (males from 6 months). 

Separately, there is also data for mixed breed dogs according to how much they weigh. That research found that there was no effect of age of spay/neuter on cancer risk, but if mixed breed dogs weigh more than 20kg, there is a greater risk of disorders of the joints if they are spayed/neutered before 12 months of age. 

The new paper details the specific health risks for the five additional breeds studied. It’s thought that in larger breeds, early neutering might affect the joints due to the later closure of the growth plates, but unfortunately research on this is lacking. The data shows that risks can be specific to certain breeds, and that in some cases there may be a need to balance the relative risks of different issues. In other words, it’s complicated. 

The study did not look at the behavioural effects of early spay/neuter, which may include increased fearfulness. As well, the scientists point out that a later spay/neuter is more costly for the dog’s guardian (as the dog is now bigger), and that older dogs take longer to recover from the surgery than puppies do.

Shelters and humane societies, and many breeders, require dogs to be spayed or neutered. According to the paper, in some areas this is even a legal requirement for shelters when they adopt dogs out, so that adopted dogs cannot reproduce.

It’s worth noting that there are big cultural differences in practices around spay/neuter, and in some countries most dogs remain intact. In the US from the mid-1970s on, shelters and humane societies stressed that responsible pet ownership included spaying or neutering your pet. This is one of the practices that has led to significant decreases over time in euthanasia rates at shelters and significant increases in adoption rates. It’s only more recently that questions have been asked about the potential health risks of this for some breeds depending on the age at which it happens. 

The decision of when to spay or neuter your dog is a complex one that should be discussed with your vet so that you get a recommendation that is specific to you and your dog. The new guidelines will be helpful for people who are concerned about the increased health risks that early spay/neuter may have in some breeds, and will help people to make informed decisions based on the risks for their breed of dog. 

What factors do you think are the most important when deciding at what age, and whether, to spay or neuter a dog?


Zazie Todd, PhD, is the award-winning author of Wag: The Science of Making Your Dog Happy and Purr: The Science of Making Your Cat Happy. She is the creator of the popular blog, Companion Animal Psychology, and also has a column at Psychology Today. Todd lives in Maple Ridge, BC, with her husband, one dog, and one cat. 

Reference

Hart, L. A., Thigpen, A. P., Hart, B. L., Willits, N. H., Lee, M., Babchuk, M. M., Lee, J., Ho, M., Clarkson, S.T. & Chou, J. W. (2024). Assisting decision-making on age of neutering for German Short/Wirehaired Pointer, Mastiff, Newfoundland, Rhodesian Ridgeback, Siberian Husky: associated joint disorders, cancers, and urinary incontinence. Frontiers in Veterinary Science, 11, 1322276. https://doi.org/10.3389/fvets.2024.1322276 

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