When Is the Best Time to Neuter German Shepherds?

New pet owners have long been urged to spay and neuter their puppies. It’s a wonderful measure to help control pet overpopulation, but does it come with a cost to the animal’s health? Researchers from the School of Veterinary Medicine at the University of California in Davis recently studied the effects of neutering in German Shepherds, and their findings may help shape new evidence-based guidelines on the best time to neuter a puppy.

The American Veterinary Medical Association supports pediatric spaying and neutering of dogs and cats, a time period which is typically after the animal is eight weeks old but before they reach six months of age. In their paper published in the journal Veterinary Medicine and Science, the University of California-Davis researchers outline their study on the veterinary hospital records of German Shepherd dogs.

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They looked at the records of 1,170 dogs spanning a period of more than 14 years and gathered data on joint disorders and cancers in both spayed/neutered and intact dogs. Their focus was on dogs eight years old and younger, as the study authors note that “beyond nine years of age the influence of neutering on health begins to fade and ageing-associated factors, such as inflammation, begin to have a great impact on a dog’s health.” In similar previous studies, this research group had also looked at Golden and Labrador Retriever dogs.

Citing previous studies, including their own, the researchers note that neutering dogs within the first year of life is associated with a higher incidence of debilitating joint disorders such as hip dysplasia (HD), cranial cruciate ligament tear or rupture (CCL) and elbow dysplasia (ED). Looking at multiple breeds, neutered dogs are two to three times more likely than intact dogs to develop CCL. The researchers’ previous study on neutered Golden Retrievers found that they have a four to five times higher incidence of joint disorders than intact dogs, which only have a 5% occurrence of these issues.

Looking at cancers such as osteosarcoma, mast cell tumors, hemangiosarcoma and lymphoma, the authors note previous studies of the Veterinary Medical Database that show that male and female neutered dogs are more likely than intact dogs to die of cancer. They also cite their own studies involving the Golden Retriever, where they found that neutering at all neuter periods through 8 years of age increased the rate of at least one of the cancers by three to four times.

For this study, the researchers compiled data from 1,170 German Shepherds. Of the 705 males, 245 were neutered and 460 were intact, and of the 465 females, 293 were neutered and 172 intact. They compared the occurrence of joint disorders in intact dogs and in those neutered before six months of age, from six to 11 months, at one year, and at two to eight years. For some of their analyses, they grouped all dogs neutered before 12 months and referred to them as early neutered.In their findings, the researchers noted that 6.6% of intact male German Shepherds experienced at least one joint disorder, as compared to 20.8% of males neutered at under six months of age. That fell to 16.4% for males neutered at six to 11 months. Hip dysplasia was the most commonly experienced joint disorder.

For intact females, joint disorders occurred in 5.1% of those studied, as compared to 12.5% in those neutered at under six months of age. The rate rose to 17% in females neutered at six to 11 months.

The authors hypothesize that neutering stems the natural gonadal hormone secretions that regulate the growth of long-bone plates, so early gonadectomy may allow the bones to grow longer than normal and thus increase the risk of joint conditions.

The rates of cancers in intact versus neutered dogs showed a much less significant change. About 3% of intact males experienced one of the forms of cancers studied, as compared to about 4.2% of neutered males. Only less than 1% of intact females experienced one form of cancer, as compared to just over 2% of the neutered females in the study.

“Dog breeds differ,” says study author Benjamin Hart, DVM, PhD. “What is the case for German Shepherds or Goldens and Labs is not true necessarily true for other breeds, like Chihuahuas. For German Shepherds, it is the timing of the neuter that is important. For this breed just waiting until the dog is well over a year of age, such as 16 to 18 months, should be sufficient to avoid increased risks of joint disorders.”

"What is the case for German Shepherds or Goldens and Labs is not true necessarily true for other breeds, like Chihuahuas. For German Shepherds, it is the timing of the neuter that is important."—Benjamin Hart, DVM, PhD

Due to their common roles as police and military dogs, the authors noted that their findings might offer valuable insight into avoiding painful conditions that can disqualify a working dog from their job. “With the current focus on avoiding joint disorders in German Shepherd dogs, the findings provided here offer some evidence-based guidelines in deciding upon the age to neuter a puppy to reduce the risk of one or more joint disorders,” the authors concluded.