Many veterinary surgeons seem to advocate spaying of bitches and neutering of dogs, but this is not a straightforward or obvious decision to make. Our DachsLife 2015 Survey found that neutered Dachshunds were nearly twice as likely to have suffered back disease (IVDD) than entire Dachshunds. Neutering under the age of 1 also resulted in higher odds of IVDD than those neutered over the age of 1. Read more about our IVDD/neutering analysis and other risks identified in DachsLife 2015. Our peer-reviewed paper "Neuter status as a risk factor for IVDD in Dachshunds" (2018).
An interesting review of the scientific literature concluded:
An objective reading of the veterinary medical literature reveals a complex situation with respect to the long-term health risks and benefits associated with spay/neuter in dogs. The evidence shows that spay/neuter correlates with both positive AND adverse health effects in dogs. It also suggests how much we really do not yet understand about this subject.
On balance, it appears that no compelling case can be made for neutering most male dogs to prevent future health problems, especially immature male dogs. The number of health problems associated with neutering may exceed the associated health benefits in most cases.
For female dogs, the situation is more complex. The number of health benefits associated with spaying may exceed the associated health problems in many (not all) cases. On balance, whether spaying improves the odds of overall good health or degrades them probably depends on the age of the dog and the relative risk of various diseases in the different breeds.
The traditional spay/neuter age of six months as well as the modern practice of pediatric spay/neuter appears to predispose dogs to health risks that could otherwise be avoided by waiting until the dog is physically mature, or perhaps in the case of many male dogs, foregoing it altogether unless medically necessary.
The balance of long-term health risks and benefits of spay/neuter will vary from one dog to the next. Breed, age, and gender are variables that must be taken into consideration in conjunction with non-medical factors for each individual dog. Across-the-board recommendations for all dogs do not appear to be supportable from findings in the veterinary medical literature.
Read the full article here. [Long-Term Health Risks and Benefits Associated with Spay / Neuter in Dogs - Laura J. Sanborn, M.S. May 14, 2007]
Another research paper is here. [Determining the best age at which to spay or neuter: An evidence-based analysis - By Margaret Root-Kustritz, DVM, PhD University of Minnesota Spring 2008]
Another interesting review of the evidence for the benefits/risks of neutering by Brennen McKenzie, MA, VMD (2009)
The effect of neutering on the risk of mammary tumours in dogs (A systematic Review, Beauvais 2012) concluded: "Due to the limited evidence available and the risk of bias in the published results, the evidence that neutering reduces the risk of mammary neoplasia, and the evidence that age at neutering has an effect, are judged to be weak and are not a sound basis for firm recommendations."
In 2016, Sundberg et al published a paper on the effects of gonadectomy on the risks of immune disorders. Neutered dogs had a significantly greater risk of 6 immune-related disorders than intact dogs. They concluded "Neutering is critically important for population control, reduction of reproductive disorders, and offers convenience for owners. Despite these advantages, the analyses of the present study suggest that neutering is associated with increased risk for certain autoimmune disorders and underscore the need for owners to consult with their veterinary practitioner prior to neutering to evaluate possible benefits and risks associated with such a procedure."
For a good article from a UK animal behaviourist read this.
Neutering: The evidence. (2016)
Neutering your dog - making an informed decision Dr Mark Elliott (2018)
This research into the effects of neutering on Golden Retrievers was published in 2013 and there is further discussion of this paper here. Listen to Dr. Hart's podcast about this research.
A literature review on the welfare implications of gonadectomy of dogs. (2017)
A review of the impact of neuter status on expression of inherited conditions in dogs. (2019)
Desexing dogs: A review of the current literature. (2019)
Self-reports of Dutch dog owners on received professional advice, their opinions on castration and behavioural reasons (2020) "Overall, most owners disagreed with or were neutral about statements on castration positively affecting male dog behaviour"
Article: Three reasons to reconsider spay/neuter
Article: Spaying & Neutering: New warnings about health problems
A 2020 paper by Hart et al looked at the evidence to support decision-making on neutering. Lead author Dr. B Hart wrote to us to say:
Thanks for sending your paper. Although the two studies are not the same, I see similar results. In our study we saw the greatest risk in IVDD in females neutered at 6-11 mo. compared to intact females. As personal advice, I suggest neutering both sexes beyond 12 mo.
Always consult your vet but, in general, our advice is that you should not have a bitch puppy spayed before its first season; it is far safer to wait until it is at least 12 months old if you must have her spayed. Similarly, dog puppies should not be neutered before they are fully mature (not before 12 months).
In our DachsLife 2018 survey we found:
For all Dachshunds aged 3-10, those neutered under 24 months were twice as likely to have reported an IVDD incident.
Odds Ratio = 2.44; P < 0.0001
For male Dachshunds aged 3-10, those neutered under 24 months were twice as likely to have reported an IVDD incident.
Odds Ratio = 1.79; P = 0.01
For female Dachshunds aged 3-10, those neutered under 24 months were four times as likely to have reported an IVDD incident.
Odds Ratio = 4.04; P < 0.0001