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Pet Health Watch with Dr. Childs
The Health Effects of Spaying and Neutering
T
he decision to spay or neuter companion animals has
been a subject of much debate for decades. When
looking at population control alone, the answer seems
simple. Humane society organizations estimate that 7.6
million animals enter the shelters in this country each
year. Unfortunately, many of these animals do not find
homes and are euthanized. Given this staggering number,
decreasing births through spaying and neutering seems
logical. In this article we will dig a little deeper.
This question still needs to be
answered by further research.
Studies on osteosarcoma (bone
cancer) and mast cell cancer were
mixed. Some show a connection
between the presence of sex
hormones and the cancer, versus
the absence of sex hormones and
the same cancer. Clearly other
factors are likely influencing the study and more research
needs to be completed.
Research is beginning to look at specific breeds
and diseases with the intent to determine if spay or
neuter plays a role in these diseases. These studies are
retrospective in nature; meaning the study looks back at
a particular population of pets. In these studies neutered
pets are compared to intact pets, however other factors
like diet, environment, medications and the like are
not controlled or consistent between subjects. Clearly
there’s a limitation to the credibility of the studies, and
never prove a true cause and effect relationship between
neutering and disease.
Relative to canine behavior it appears that the neutered
male is less likely to show roaming, mounting, urine
marking and aggressive behavior. However in the areas
of separation anxiety, storm phobias, and fear behavior
there may be a link to the animal neutered prior to six
months. These studies involved small numbers and no
firm conclusions were made.
Orthopedic conditions have been looked at as well with
some preliminary retrospective studies showing that early
spay or neuter could be linked to the development of hip
dysplasia, elbow dysplasia, and injury to the anterior crucial
ligament. Again these studies are crude and not controlled.
I admire the scientific query here, and the desire to
determine new ways to limit the expression of disease.
Yet, there is limited evidence to link gonadectomy
to various diseases. Further there is clear evidence
to support that neutered animals are associated with
increased longevity.
The quest to link disease to neutered animals needs to
be further studied with appropriately designed research
studies. The decision to spay or neuter should be
made individually with the veterinarian. At this time the
evidence leading to the decision to delay neutering to
attain health benefits is not founded.
Perhaps the most meaningful finding of these
retrospective studies is that neutered animals are
associated with an increased lifespan. Despite this
general statement it might play out differently with
certain diseases and breeds. Let’s look at a couple
specific studies.
It’s possible that pet owners who neuter their pets also visit
their veterinarian more regularly. The more regular visits
lead to more and earlier diagnoses, which in turn effects
the studies. This compares to the intact dog that rarely
visits the veterinarian, yielding no documented diagnoses
to be found in the studies. The most telling finding in these
studies, is likely that neutered pets live longer.
In the case of hemangiosarcoma, a malignancy of
the blood vessel which often effects the spleen, there
appears to be an increased incidence in the spayed
female especially in the Swiss Mountain Dog and
Vizsla. The real question is whether sex hormones
have a protective effect on the body against cancer.
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