Summary: Final update on findings at the end-year 2 in a study to develop a generalized understanding of the impact of early spay and neuter on disease risk in dogs. The goal of this project was to evaluate, using one consistent and uniform database at their large veterinary medical center (UC Davis). This update provides conclusions for several medium-to-large breed dogs regarding the impact of early spay/neuter on cancer and musculoskeletal risks. Several additional breeds were evaluated since last update. Additionally, several small breeds were evaluated determining negligible risk with early spay/neuter. Findings indicate risk vary from breed to breed.
The long-term goal of this project is to evaluate the breed-specific effects of neutering (both sexes) at different ages on joint disorders (hip dysplasia, cranial cruciate ligament tear and
elbow dysplasia) and some cancers (lymphosarcoma, hemangiosarcoma, mast cell tumor). The effects of neutering at various ages were also examined in females with regard to
mammary cancer, urinary incontinence and pyometra. The breeds examined were: Labrador Retrievers, German Shepherd Dogs, Dachshunds, Boxers, Rottweilers and Chihuahuas,
Yorkshire Terriers, Shih Tzus, Corgis (two breeds combined for analyses), Doberman Pinschers and Bulldogs. In the space below, we will provide a summary of the findings.
Labrador Retriever (1,500 cases: males–272 neutered, 536 intact; females–347 neutered, 345 intact)
The findings on the Labrador Retriever are published. The major finding was a significant 2-fold increase in one or more joint disorders with neutering in the first year in both males and
females above the 5 percent level of intact dogs. The occurrence of the cancers followed was low (3-4%) and not affected by neutering.
German Shepherd Dog (1,170 cases)
The paper is under review. Early neutering significantly increased the incidence of one or more joint disorders and the occurrence of the cancers followed was low and not affected by
neutering.
Small-dog Breeds
Chihuahua (831 cases)
Yorkshire Terrier (553 cases)
Shih Tzu (322 cases)
These breeds lacked joint disorders associated with neutering at any age above the low incidence of intact dogs. The occurrence of one or more cancers was low in both intact and
neutered dogs.
Long-dog breeds
Dachshund (548 cases)
Corgis (191 cases)
Joint disorders in these breeds were not associated with neutering at any age above the low incidence of intact dogs. The occurrence of one or more cancers was low in both intact and
neutered dogs. In male and female Dachshunds the occurrence of intervertebral disc disorders was high in intact dogs and not increased by neutering.
Rottweiler (696 cases)
Males and females showed an increase above intacts in one or more joint disorders with early neutering. The incidence of one or more of the cancers was not increased in either gender by neutering at any age.
Boxer (645 cases)
There was no increase in joint disorders associated with neutering at any age above the low incidence in intact dogs. Intact males had a fairly high incidence of cancers, which was
increased in one of the neuter periods. Intact females had a fairly high incidence of cancers, not increased by neutering.
Doberman Pinscher (295 cases)
In males, there was no increase in one or more joint disorders associated with neutering above the low level in intact males. In females, however, there was an elevated incidence of joint
disorders in an early neuter period, compared to none in intact females. In both sexes, the occurrence of cancers was less than the low level in intact dogs and not markedly affected by
neutering.
Bulldog (471 cases)
The moderate occurrence of one or more joint disorders in intacts appeared not to be increased with neutering in males and females. For cancers, there was no evident increase in
occurrence associated with neutering above the moderate level of intact male and female dogs.
