1 Sept 2020
“Clear-cut” results from University of California, Davis study recommends – in dogs that will be more than 20kg bodyweight as adults – neutering should be delayed until they are at least one year old.
John Bonner
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Image © trwirth / Pixabay
Neutering large, mixed-breed dogs before they reach sexual maturity may triple the risk that they will go on to develop joint disease, researchers have shown.
A study by Benjamin and Lynette Hart’s team from the University of California, Davis (UC Davis) School of Veterinary Medicine analysed data from 50,000 canine patients seen over a 20-year period, and compared the incidence of cranial cruciate injury and hip or elbow dysplasia in both neutered and intact dogs of different bodyweights.
Prof Benjamin Hart said: “The results are clear-cut. For dogs that will be more than 20kg bodyweight as adults you should delay neutering until at least one year old. For smaller dogs weighing less than 20kg, the procedure can be done at any time.”
The paper, in the journal Frontiers in Veterinary Science, offers guidelines for the ideal age at neutering for male and female dogs in five weight categories – small (less than 10kg), medium (10kg to 19kg), standard (20kg to 29kg), large (30kg to 39kg) and giant (more than 40kg).
For those in the first two groups, no increased risk was seen for any age at neutering for either sex.
For heavier animals, it recommended waiting until the animal is at least 11 months old, and for males belonging to giant breeds it may be necessary to delay for a further year.
But a decision on which animals should be left intact until much later is not always straightforward, as Prof Lynette Hart pointed out.
She said: “People like to adopt puppies from shelters, but with mixed breeds it may be difficult to determine just how big the dog will become if you don’t know anything about its parents.”
Prof Benjamin Hart suggested that mixed‑breed dogs will often have physical characteristics that give some indication of the breed to which their parents belonged. Paw size is also a reasonably useful indicator of its eventual weight, he said.
David Yates, former head vet at the RSPCA clinic in Manchester, commended the study as “an excellent piece of research that will be useful for vet practitioners when engaging in a discussion with clients about the timing, and the risks and benefits of neutering – especially in large breeds”.
