Cats who’ve lost their reproductive organs at a very young age may also lose some bravado, according to a new study that found increased levels of shyness among those who’d been spayed and neutered when they were less than 5.5 months old.

But what they gain more than makes up for it—namely, a decrease in the occurrence of hyperactivity, asthma, and gingivitis. For males, there are even more benefits, including fewer abscesses, decreased expression of sexual behaviors, less urine-spraying, and less aggression toward veterinarians (arguably more of a benefit for the vets than for the cats).

© ANGIE KNOST

Conducted by researchers at Cornell University and published in the Journal of the American Veterinary Medical Association,* the study followed the progress of sterilized cats for up to 11 years after surgery. All 1,660 spayed and neutered cats involved in the project had been adopted as kittens under the age of one from the SPCA Serving Erie County in New York between 1989 and 1998. To track behavior information and medical data on all the cats, researchers interviewed the cats' owners and studied veterinary records at local clinics.

The goal of the project was to compare outcomes of pediatric spay/neuter and traditional-age surgery (performed at six months or older) by examining differences in overall mortality rates, medical and behavioral histories, and retention levels.

Though other studies have demonstrated the benefits of early-age spay/neuter, some veterinarians still associate pediatric sterilization with a greater risk of developing diabetes, immune deficiencies, obesity, skin disease, and urinary tract obstruction later in life, the researchers wrote. This most recent project may help assuage those fears, though, since none of these conditions were found to be related to age at the time of sterilization. “Therefore, concerns about these conditions should not be used as a reason to delay castration of male cats,” wrote the researchers.

“Animal shelters can safely gonadectomize cats at a young age,” they wrote, “and veterinarians should consider recommending routine gonadectomy for client-owned cats before the traditional age of 6 to 8 months.”

While the study found more shyness tendencies among both male and female cats sterilized at an early age—as well as an increased propensity for hiding among male cats who’d been neutered before 5.5 months— the researchers note that these associations had not been previously suspected. “Because these are behaviors that may appear after a stressful event (e.g., adoption) and later resolve,” they wrote, “we cannot fully determine whether these behaviors were longterm effects of early-age gonadectomy or simply behaviors associated with being adopted at a young age.”

The researchers point out that other spay/neuter options for reducing the numbers of unwanted animals are not as effective as surgical pediatric sterilization: Contracts requiring adopters to spay and neuter animals are often broken, or adopters don’t perform the surgery until after their new cat has had a litter of kittens. And chemical sterilization, while potentially useful in the future, is available only for male puppies at this point.

Pediatric spay/neuter is both effective and safe, the authors conclude, and enables shelters to ensure the cats they place in the community will not contribute to the pet homelessness problem.

The Dog Study

When dogs are spayed or neutered at a very young age, their risk of relinquishment decreases, as do many of the behaviors that often lead to the relinquishment in the first place.

That’s according to a new study conducted alongside the research project on pediatric sterilization of cats, written by Cornell University scientists, and published in the same edition of the Journal of the American Veterinary Medical Association.

© CRIS. M. KELLY

As with the cat study, the researchers examined behavioral and medical histories of dogs who had been adopted from the SPCA Serving Erie County while still less than one year old. The dogs had been placed into their adoptive homes between 1989 and 1998; some had undergone spay/neuter surgery at less than 5.5 months of age, while others had undergone the surgery at 5.5 months or older.

A study of potential long-term effects produced more complicated results for dogs than for cats. Though male and female dogs who’d been sterilized at the earlier age were less prone to obesity, separation anxiety, escaping behaviors, and inappropriate elimination when frightened, the incidence of hip dysplasia, noise phobias, and sexual behaviors was higher among this group. Female dogs spayed at the earlier age had an increased rate of cystitis and urinary incontinence as well.

Those results led to mixed recommendations from the authors, who were in favor of pediatric sterilization overall but said that delaying the spaying of female dogs until at least three months “may be beneficial.”

But even though the incidence of urinary incontinence requiring medical treatment was 12.9 percent among early-spayed female dogs, the condition did not appear to affect the animal’s status in the home or the pet-to-owner relationship. “None of the 49 female dogs with urinary incontinence ... were relinquished to a shelter or given to another owner for any reason,” wrote the researchers, “and their rate of euthanasia was not higher than the overall rate.”

While delaying the spaying of female dogs until they are at least three or four months old is probably the most medically sound practice, it may not be the one all shelters choose, the researchers wrote. “[It] may be particularly prudent for a shelter that does not have an excess of puppies and is focused on reducing medical and behavioral conditions that could lead to relinquishment of adolescent and adult dogs,” they wrote. “Conversely, for shelters with excess puppies, the advantages of gonadectomy of all dogs before adoption may outweigh the risk of urinary incontinence.”

Unlike cats, who were more shy if they’d been spayed or neutered earlier, male dogs who’d undergone pediatric sterilization barked more and growled more at visitors, but not enough for owners to consider it a serious problem. Aggression toward family members was also more prevalent. But, wrote the researchers, “these associations were probably an artifact of the shelter’s screening procedure for aggression and not a result of early-age gonadectomy.” In other words, the shelter does not conduct temperament evaluations on puppies, so aggression among that group may not be identified until later. Since older dogs displaying severe aggression had been euthanized following screening, the authors explained, aggressive dogs spayed and neutered at the traditional or later age were probably underrepresented in the original sample.

Reasons for the increase in noise phobias among early-age sterilized dogs were not clear to the authors, who thought it could have also been a manifestation of being adopted at a young age. Likewise, the greater incidence of sexual behaviors among early-age neutered dogs could have been due to something other than the pediatric surgery: Researchers surmise that perhaps the pet owners surveyed characterized the behaviors as “sexual” ones even if they were merely playful. None of the behaviors described as such were associated with aggression, and only 2.5 percent of adopters thought their dogs had a serious problem with sexual behaviors.

Though veterinarians have long suspected that early-age spay/neuter leads to overweight dogs, the study found that the proportion of overweight dogs was lowest among those who’d undergone pediatric sterilization. A lower frequency of escaping behaviors was another positive outcome of early-age surgery, as a decrease in these behaviors could lead to a reduced incidence of roaming, the authors suggest.

“Thus, other than aggression and excessive barking among males, which could not be evaluated well with our study, all behavioral conditions with serious consequences were less frequent among the early-age gonadectomized dogs,” they wrote. In other words, many of the behaviors that have been identified as leading causes of relinquishment were the least prevalent in those dogs who’d undergone pediatric sterilization.

“Because early-age gonadectomy appears to offer more benefits than risks for male dogs, animal shelters can safely gonadectomize male dogs at a young age,” the researchers wrote, “and veterinary practitioners should consider recommending routine gonadectomy for client-owned male dogs before the traditional age of 6 to 8 months.”

Reproduced from the March-April 2004 issue of Animal Sheltering magazine.