New Study: Neutering Affects Dog Health

University of California, Davis


February 13, 2013



GOLDEN RETRIEVER STUDY SUGGESTS NEUTERING AFFECTS DOG HEALTH



Neutering, and the age at which a dog is neutered, may affect the animal's risk

for developing certain cancers and joint diseases, according to a new study of

golden retrievers by a team of researchers at the University of California,

Davis.



The study, which examined the health records of 759 golden retrievers, found a

surprising doubling of hip dysplasia among male dogs neutered before one year of

age. This and other results will be published today (Feb. 13) in the online

scientific journal PLOS ONE at http://dx.plos.org/10.1371/journal.pone.0055937



"The study results indicate that dog owners and service-dog trainers should

carefully consider when to have their male or female dogs neutered," said lead

investigator Benjamin Hart, a distinguished professor emeritus in the UC Davis

School of Veterinary Medicine.



"It is important to remember, however, that because different dog breeds have

different vulnerabilities to various diseases, the effects of early and late

neutering also may vary from breed to breed," he said.



While results of the new study are revealing, Hart said the relationship between

neutering and disease-risk remains a complex issue. For example, the increased

incidence of joint diseases among early-neutered dogs is likely a combination of

the effect of neutering on the young dog's growth plates as well as the increase

in weight on the joints that is commonly seen in neutered dogs.



Dog owners in the United States are overwhelmingly choosing to neuter their

dogs, in large part to prevent pet overpopulation or avoid unwanted behaviors.

In the U.S., surgical neutering -- known as spaying in females -- is usually

done when the dog is less than one year old.



In Europe, however, neutering is generally avoided by owners and trainers and

not promoted by animal health authorities, Hart said.



During the past decade, some studies have indicated that neutering can have

several adverse health effects for certain dog breeds. Those studies examined

individual diseases using data drawn from one breed or pooled from several

breeds.



Against that backdrop, Hart and colleagues launched their study, using a single

hospital database. The study was designed to examine the effects of neutering on

the risks of several diseases in the same breed, distinguishing between males

and females and between early or late neutering and non-neutering.



The researchers chose to focus on the golden retriever because it is one of the

most popular breeds in the U.S. and Europe and is vulnerable to various cancers

and joint disorders. The breed also is favored for work as a service dog.



The research team reviewed the records of female and male golden retrievers,

ranging in age from 1 to 8 years, that had been examined at UC Davis' William R.

Pritchard Veterinary Medical Teaching Hospital for two joint disorders and three

cancers: hip dysplasia, cranial cruciate ligament tear, lymphosarcoma,

hemangiosarcoma and mast cell tumor. The dogs were classified as intact (not

neutered), neutered early (before 12 months age), or neutered late (at or after

12 months age).



Joint disorders and cancers are of particular interest because neutering removes

the male dog's testes and the female's ovaries, interrupting production of

certain hormones that play key roles in important body processes such as closure

of bone growth plates, and regulation of the estrous cycle in female dogs.



The study revealed that, for all five diseases analyzed, the disease rates were

significantly higher in both males and females that were neutered either early

or late compared with intact (non-neutered) dogs.



Specifically, early neutering was associated with an increase in the occurrence

of hip dysplasia, cranial cruciate ligament tear and lymphosarcoma in males and

of cranial cruciate ligament tear in females. Late neutering was associated with

the subsequent occurrence of mast cell tumors and hemangiosarcoma in females.



In most areas, the findings of this study were consistent with earlier studies,

suggesting similar increases in disease risks. The new study, however, was the

first to specifically report an increased risk of late neutering for mast cell

tumors and hemangiosarcoma.



Furthermore, the new study showed a surprising 100 percent increase, or

doubling, of the incidence of hip dysplasia among early-neutered males. Earlier

studies had reported a 17 percent increase among all neutered dogs compared to

all non-neutered dogs, indicating the importance of the new study in making

gender and age-of-neutering comparisons.



Other researchers on this UC Davis study were: Gretel Torres de la Riva, Thomas

Farver and Lynette Hart, School of Veterinary Medicine; Anita Oberbauer,

Department of Animal Science; Locksley Messam, Department of Public Health

Sciences; and Neil Willits, Department of Statistics.



About UC Davis



For more than 100 years, UC Davis has engaged in teaching, research and public

service that matter to California and transform the world.

Located close to the state capital, UC Davis has more than 33,000 students, more

than 2,500 faculty and more than 21,000 staff, an annual research budget of

nearly $750 million, a comprehensive health system and 13 specialized research

centers. The university offers interdisciplinary graduate study and more than

100 undergraduate majors in four colleges -- Agricultural and Environmental

Sciences, Biological Sciences, Engineering, and Letters and Science. It also

houses six professional schools -- Education, Law, Management, Medicine,

Veterinary Medicine and the Betty Irene Moore School of Nursing.



Media contact(s):

* Benjamin Hart, School of Veterinary Medicine, (530) 752-1555,

blhart@ucdavis.edu

* Pat Bailey, UC Davis News Service, (530) 752-9843, pjbailey@ucdavis.edu



View this story on the Web at

http://news.ucdavis.edu/search/news_detail.lasso?id=10498



Trina Wood, Communications Officer

UC Davis School of Veterinary Medicine

Office: 530-752-5257

tjwood@ucdavis.edu



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