The recommendation to spay and neuter all dogs is the
standard of care, but recent evidence has thrown new light on that dogma – at least
for two breeds.
Two studies from the University of California-Davis School
of Veterinary Medicine have taken the veterinary world by surprise. The research was based on 13 years of health
records from UC-Davis for neutered and non-neutered male and female Labrador and
golden retrievers between 6 months and 9 years of age. The most
recent study, published in July of this year, compared 1,015 goldens with
1,500 Labs. Those two breeds were chosen
because of their popularity, similar size, and comparable behavioral
characteristics.
The researchers picked several
cancers (lymphosarcoma,
hemangiosarcoma,
mammary cancer, and mast
cell tumor) and three joint disorders (hip
dysplasia, cranial cruciate ligament tear, and elbow dysplasia) and
compared the incidence in neutered and non-neutered dogs of both breeds. The neutered dogs were grouped into four
categories, according to the age at which they had been altered.
It turned out that non-neutered males and females of both
breeds had a 5 percent rate of one or more joint disorders. But in Labs, neutering before 6 months of age
doubled that rate, to 10 percent. More
alarming, the golden retrievers that had been neutered before 6 months of age had
4 to 5 times the incidence of joint disorders compared with non-neutered
goldens. The joint disorders found to
increase in male goldens were hip dysplasia and cranial cruciate ligament
tears, while lab males had more cruciate tears and elbow dysplasia.
Lead investigator Dr. Benjamin Hart at UC-Davis says, “The effects of neutering during the first
year of a dog’s life, especially in larger breeds, undoubtedly reflects the
vulnerability of their joints to the delayed closure of long-bone growth plates
when neutering removes the sex hormones.”
In other words, we’re messing with Mother Nature!
Regarding cancers, the data also uncovered significant
differences between the breeds. The
cancer rate of both breeds when they weren’t neutered was 3 to 5 percent,
except in male goldens, who have an 11 percent cancer rate. Neutering didn’t have much effect on the
cancer rate of male goldens. However, in
female goldens, neutering at any point beyond 6 months increased the risk of some
cancers to 3 to 4 times the level of non-neutered females. But that was true only for goldens; neutering
female labs only negligibly increased their cancer rate. According to Dr. Hart, “The striking effect of
neutering in female golden retrievers … suggests that in female goldens the sex
hormones have a protective effect against cancers throughout most of the dogs’
lives.” Mother Nature again.
What
does all this mean? Should we stop
neutering our dogs to prevent joint disease and cancer? Before sweeping changes are made, the
limitations of the studies must be discussed.
First of all, they compared Labs with goldens; no other breeds were
studied. Comparing goldens with German shepherds
probably would yield vastly different results. Even within a breed, there were
significant differences based on gender.
To get solid data, hundreds of studies would have to be done, not just on a breed basis, but also on a gender
basis.
When I started practicing veterinary medicine in 1977, the
unwavering recommendation almost every veterinarian made was to neuter all dogs
at 6 months of age. I don’t think
compliance was nearly as good then as it is today. I remember many male dogs coming in with
prostate problems, perianal tumors, and perineal hernias, all conditions associated
with not being neutered. Spaying a
female of any breed before her first heat has been associated with a lowered
risk of breast
tumors; performing surgery on unspayed dogs to remove breast cancer and infected
uteruses was a frequent occurrence back then. I rarely see those medical problems today; it’s
likely that the early neutering of pets from shelters has had a big influence
on preventing them.
The two studies looked only at the risks of neutering those breeds, but not at the benefits. Neutering a female golden, for example,
elevated the risk of one or more cancers three- to fourfold. But not spaying dogs of all breeds causes the
above-mentioned breast cancer and infected uteruses, as well as messy heats and
the risk of overpopulation. You might
prevent joint disease in your male Lab by leaving him intact, but in addition
the problems I listed above, the compromise might be aggression, wandering,
marking in the house, and, again, unwanted puppies.
So now we veterinarians and our clients are faced with a
quandary: to fix or not to fix. I
think it’s wise to discourage neutering in goldens and Labs before 6 months of
age, and 12 months is even better. I
also think a discussion is warranted with the owners of other large-breed dogs,
whose joints are more vulnerable when they are altered early. As far as never neutering, we need more data
before we make a blanket recommendation across all breeds. For the owners of Labs and goldens, we can
discuss the risk-benefit ratio with you, but the decision as to whether to
neuter will ultimately be yours.
