Spay/Neuter of Shelter Animals
Pediatric Spay/Neuter
Facts About this Safe and Effective Procedure
Pediatric spay/neuter is the subject of ongoing debates among veterinarians
that is fraught with misinformation, misconceptions and high emotions.
Although millions of domesticated animals have been surgically sterilized,
many veterinarians believe sufficient conclusive research has not been
conducted to determine the best age or reproductive stage of life to spay
and neuter dogs and cats.
However, studies have been conducted that show that pediatric spay/neuter is
safe and effective in both the short and long term. This information can
help allay many of the veterinarian's fears so they may embrace the concept
as readily as they embrace neutering at 6 months of age.
Early Age Spay/Neuter Defined
The harshest criticism by veterinarians of early age neutering is usually
reserved for surgeries performed on animals as young as 6-8 weeks of age or
under 2 pounds of body weight. But early age spay/neuter should be broadly
defined as surgical sterilization procedures performed on animals who are
6-16 weeks of age or under the traditional age of 6 months. Using that
definition, surgery performed on a 4-month old female animal would be
considered a pediatric spay.
Because the term "early" implies that the procedure is being performed
prematurely, some veterinarians proposed that alternative language might be
more acceptable. Some alternative terms for early age spay/neuter include:
* Juvenile spay/neuter
* Pediatric spay/neuter
* Prepuberal spay/neuter
* Prepubertal spay/neuter
* Prepubescent spay/neuter
History of Spaying and Neutering
Many veterinarians are not aware of the different theories that have been
advanced regarding the timing of spaying a female cat or dog. Both
veterinarians and the general public might be surprised to know that in the
early 1900s, veterinarians advocated spaying bitches between 3 and 6 months
of age, or even prior to weaning, and castration was done as early as 4
weeks of age. At one time it was believed that it was beneficial for animals
to have a litter before being spayed, while another prevailing school of
thought, until fairly recently, was that animals should go through one heat
before being spayed.
Many veterinary colleges are currently teaching that spaying and neutering,
also known as gonadectomy, can be done safely at any age, but believe that
pediatric spay/neuter is a tool mainly for population control for shelter
animals only. However, pediatric spay/neuter should be considered for
animals belonging to the general public as well.
Revisiting the Six-Month Recommendation
Six months of age is generally considered to be the standard recommendation
for spaying and neutering puppies and kittens. It is unclear from the
scientific literature how that conclusion was reached.
It is now known that spaying an animal before the first heat prevents the
development of mammary gland tumors later in life. Since kittens may go into
heat at 4 months of age, waiting until 6 months risks accidental pregnancy
and loses the protection against mammary gland cancer.
It would appear that decisions about when to spay and neuter are based more
on the individual practitioner's comfort level and familiarity with the
surgical technique and anesthesia rather than on any sound scientific or
medical evidence.
The six month age requirement for surgery came into question in the late
1970s when shelters encountered difficulty getting adopters to comply with
contractual agreements to neuter their newly adopted pets. Despite various
incentives, many adopters simply refused to abide by the agreements once
they had acquired the animals.
Some shelters found that litters from animals they had adopted out were
being brought back to them, and that they were thus actually contributing to
the overpopulation problem. They decided the best solution would be to
neuter the animals before they were adopted, but the six month age
restriction meant that puppies and kittens could not be altered.
Once it was determined that no compelling medical reason could be found in
the veterinary literature to wait until the animals were six months of age,
pediatric surgeries began to be performed. Dr. Leo Lieberman is the
acknowledged pioneer of pediatric spay/neuter. He began performing the
surgeries in the late 1970s, and they have been performed by shelters ever
since.
A Growing Body of Evidence
In 1993 Faggella and Aronsohn published surgical and anesthetic protocols in
the Journal of the American Veterinary Medical Association (JAVMA) for
safely neutering animals as young as 6 weeks of age. Although the surgeries
had already been performed safely on thousands of shelter animals, these
articles provided the much-needed research data to prove that the procedures
were indeed safe to perform.
On July 18, 1993, the American Veterinary Medical Association (AVMA) House
of Delegates approved a resolution on early age spay/neuter which stated:
"Resolved that the AVMA supports the concept of early (8-16 weeks of age)
ovariohysterectomies/ gonadectomies in dogs and cats, in an effort to stem
the overpopulation problem in these species."
Aware of the controversy surrounding this statement they also added:
"The concept is for the benefit of animal shelter and humane society
spay/neuter programs. Individual veterinarians have the right/responsibility
to decide at what age they will perform the procedure."
In 2004, the policy was revised and the "concept" portion of the statement
was removed.
Throughout the 1990s, groups such as the American Animal Hospital
Association (AAHA), American Society for the Prevention of Cruelty to
Animals (ASPCA), American Humane Association (AHA), Cat Fanciers Association
(CFA), American Kennel Club (AKC), Humane Society of the United States
(HSUS), and the California Veterinary Medical Association (CVMA) endorsed
pediatric spay/neuter.
Despite these endorsements and the body of evidence already gathered through
research and anecdotal information from over 25 years of performing
pediatric procedures, the debate still goes on. This information should help
resolve some of the problems and concerns.
Concerns about Pediatric Spay/Neuter
An often-cited concern regarding pediatric spay/neuter is a lack of
sufficient scientific data regarding long-term consequences. The following
are commonly discussed issues:
* Obesity
* Stunted growth
* Cranial cruciate ligament rupture
* Hip dysplasia
* Behavioral problems
* Lower urinary tract disease
* Secondary sex characteristics
* Urinary incontinence
* Infectious disease
* Hypothyroidism
* Diabetes mellitus
* Neoplasia
General Concerns about the Long-Term Effects
The results of studies of the long-term outcome of gonadectomies performed
at an early age or traditional age in cats and dogs were published in JAVMA
in the December 1, 2000 and January 15, 2001 issues, respectively. The
studies were performed at the Texas A&M Veterinary College by Dr. Lisa Howe
on 269 dogs and 263 cats from animal shelters.
The conclusion for dogs was that "with the exception of infectious diseases,
prepubertal gonadectomy may be safely performed in dogs without concern for
increased incidence of physical or behavioral problems during at least a
4-year period after gonadectomy."
Shelters that held puppies long-term encountered problems with parvovirus.
However, the authors of this paper did not conclude that prepubertal
gonadectomy caused parvovirus. The puppies in the study were at an age where
they were susceptible to parvovirus and housed in a shelter environment
where parvovirus can be common; they developed parvovirus for these reasons,
and not because they were sterilized as pediatric patients. (Studies have
also shown that, unrelated to surgery, the longer animals are held in
shelters, the more likely they are to become ill. Shelters that held puppies
short-term did not encounter similar disease problems.)
The conclusion for cats was that "prepubertal gonadectomy may be performed
safely in cats without concern for increased incidence of physical or
behavioral problems for at least a 3-year period after gonadectomy."
Another study addressing the long-term effects of pediatric spay/neuter was
published in JAVMA in the February 1, 2004 issue. This study was performed
at the Cornell University College of Veterinary Medicine by Dr. Vic Spain,
who looked at the records of shelter animals (1,842 dogs and 1,660 cats) who
were sterilized as pediatric patients. This study provided follow-up for as
long as 11 years.
The conclusion for dogs was that "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 and veterinary practitioners should
consider recommending routine gonadectomy for client-owned male dogs before
the traditional age of 6 to 8 months. For female dogs, however, increased
urinary incontinence suggests that delaying gonadectomy until at least 3
months of age may be beneficial." It is important to note that the female
dogs with reported urinary incontinence remained in their homes and were not
relinquished to the shelter. The long-term Texas A&M study did not find
similar results about urinary incontinence, and another study from 1992
showed a higher incidence of urinary incontinence in female dogs spayed
AFTER the first estrus cycle.
The conclusion for cats from the Cornell study was that "Gonadectomy before
5.5 months of age was not associated with increased rates of death or
relinquishment or occurrence of any serious medical or behavioral condition
and may provide certain important long-term benefits, especially for male
cats. Animal shelters can safely gonadectomize cats at a young age and
veterinarians should consider recommending routine gonadectomy for
client-owned cats before the traditional age of 6 to 8 months."
It should be noted that similar focused studies have not been conducted to
establish the long-term safety of gonadectomies performed at 6 months of
age.
Obesity
Obesity is influenced by a number of factors, and while neutered animals do
have a tendency to weigh more than intact animals, it occurs regardless of
whether the surgery was performed prepubertally or at the conventional age
of six months. A published study in 1991 indicated that dogs did not develop
obesity when they were sterilized at either pre or post puberty. Another
study from 1996 showed that cats can gain weight after gonadectomy, but this
is for both gonadectomy at the traditional age as well as prepubertal.
It should be stressed again that obesity is a multi-factorial problem. Even
an intact animal can become obese if a proper diet and exercise regimen is
not followed. Just as in humans, dietary indiscretions and lack of activity
are the real culprits in this case.
Growth
Many veterinarians erroneously believe that pediatric spay/neuter will stunt
the growth of animals. In fact, the exact opposite is true. This concern
about stunted growth following prepubertal gonadectomy has been refuted by
multiple studies.
In contrast to intact dogs, pups spayed or neutered at 7 weeks of age and
male pups neutered at 7 months of age had greater final radius and ulna
lengths. The removal of hormonal influences on the growth plates of the long
bones results in delayed closure, resulting in bones that are actually a
little longer. However, no clinical significance to this difference in size
has been found.
In cats, although prepubertal gonadectomy had a similar effect of delayed
closure of the growth plates, this did not lead to clinically significant
differences in the final length of the long bones.
Cranial Cruciate Ligament Rupture
In humans, cranial cruciate rupture (CCL) is more common in women than men
and may be more likely to occur during certain phases of the menstrual
cycle, which may be due to a hormonal effect on joint stability (Root
Kustritz). Reported incidence of rupture of the CCL in dogs is 1.8%, and
this is reportedly more common in sterilized female and male dogs than in
intact dogs (Root Kustritz).
The exact cause and effect relationship has not yet been defined, but in
addition to the suspected hormonal influence, heredity, body weight, and
body condition score may all play a role in CCL rupture (Root Kustritz).
There have not been any studies that have shown that delayed closure of the
growth plates of the long bones results in asynchrony and/or abnormalities
in joint formation as a cause of CCL rupture in dogs.
Hip Dysplasia
Long term studies have looked at the incidence of hip dysplasia in dogs and
the association of hip dysplasia with pediatric spay/neuter (Howe, personal
communication). The reported incidence of hip dysplasia is 1.7% with an
increased incidence in large and giant-breed dogs (Root Kustritz). In the
long term Cornell study, puppies that underwent pediatric spay/neuter before
5.5 months of age had an increased incidence of hip dysplasia. However, an
additional finding of this study was that dogs that were gonadectomized at
the traditional age were three times more likely to be euthanized for the
hip dysplasia as compared to the early gonadectomized group. The authors
suggest that early age gonadectomy may be associated with a less severe form
of hip dysplasia (Howe, personal communication).
Behavior
The effects of pediatric spaying and neutering on behavior remain largely
unknown. Sterilization and the subsequent decrease in related hormones have
been correlated with a decrease in gender-specific behaviors. Neutering at
any age reduces the urge of male animals to spray urine to mark territory,
roam and fight with other male animals. The demonstration of sexual
behaviors in male cats can make them undesirable house pets, and a decrease
in such behaviors is a powerful benefit of having them neutered. Also, the
trainability of working dogs is not altered by gonadectomy and does not vary
with age of the dog at time of surgery (Root Kustritz).
The large Cornell study of dogs sterilized before 5.5 months of age
indicates an increase in noise phobias and sexual behaviors and a decrease
in escaping, separation anxiety, and urination in the house when frightened
(Spain, Scarlett, Houpt, 2004). However, a different study showed no
difference in the incidence of overall or specific behavioral problems
between early-age and traditional-age sterilization (Howe, 2001).
There is some early evidence that animals that are gonadectomized at 7 weeks
or 7 months of age are more active and excitable, and that male and female
cats may be more affectionate than those left intact, but this is a fairly
subjective observation that requires more research to substantiate. There
does not appear to be any clinical significance to any observed behavioral
differences.
Lower Urinary Tract Disease
Pediatric spay/neuter has not been found to contribute to a higher rate of
urinary tract obstructions in male cats. Studies have been conducted on male
cats to determine the incidence of urinary tract obstructions in all
populations. It was found that the diameter of the penile urethra did not
vary between animals neutered at 7 weeks or 7 months of age or from intact
male cats.
It was originally believed that castrated cats had a higher incidence of
urinary tract blockages, but this is not the case. The penis in male dogs
castrated at 7 weeks of age is smaller as is the os penis, and preputial
development is juvenile in comparison with dogs castrated at 7 months of age
or left intact, but there has been no clinical significance attached to
Posts
