Excerpted with permission from Root Kustritz MV. Optimal age for gonadectomy in dogs and cats. Clinical Theriogenology 2010;2:177-181.
Ovariohysterectomy and castration are the surgeries most commonly performed by small animal practitioners in the United States.
Exhaustive reviews of the benefits and detriments of gonadectomy at various ages have been published. This is a brief review
of the literature to inform decisions regarding best age at which to perform castration or ovariohysterectomy in dogs or cats.
Optimal age at which to perform ovariohysterectomy (OHE) or castration of dogs and cats is not defined by the veterinary literature.
In the United States, most veterinarians recommend cats and dogs be spayed or castrated when about 6 months of age, prior
to puberty, which is defined as acquisition of normal breeding behavior and semen quality in males and first estrus in females.
In other countries, veterinarians recommend that dogs and cats be spayed after their first estrus, or do not recommend elective
surgical sterilization be performed at any age. Indeed, in some countries, elective gonadectomy is considered unethical and
is either strongly discouraged or illegal. For this discussion, it is assumed that the veterinarian is comfortable with the
ethics of elective gonadectomy and practices in a country in which such surgery is considered acceptable by professional associations
and society at large.
Dogs and cats can be considered as part of a larger population of animals or as individuals. Recommendation for age at which
to perform elective gonadectomy must take this into account. Animals at humane organizations that are not yet associated with
a responsible owner or guardian should be evaluated as part of the larger population. Dogs and cats with an owner or guardian
may be considered either as part of a larger population or as an individual.
Dogs and cats with no owner or guardian
In the United States, a serious problem with pet overpopulation exists, such that millions of unowned dogs and cats are euthanized
yearly. Some of these are feral animals, some are abandoned and brought to the humane association as strays, and many are
relinquished. Intact animals are much more likely to be relinquished than are spayed or castrated animals and animals that
are adopted out from the humane association while still intact may either be returned or repopulate that shelter with their
offspring. While most intact animals are adopted out with a spay-neuter contract, compliance with such contracts has been
demonstrated to be less than 60%. There is a significant lack of knowledge among pet owners regarding normal reproduction;
studies have demonstrated that up to 57% of bitch owners were unaware that bitches cycle at least twice yearly, up to 83%
of queen owners were unaware that queens are polyestrous from spring to early fall, and up to 61% of dog and cat owners were
unsure or believed that their animal would somehow be "better" after having had at least one litter. In one survey of dog-
and cat-owning households, 56% of 154 canine litters and 68% of 317 feline litters were unplanned, with the majority of those
owners reporting that they did not know the female had been in heat. While everyone would like to believe that better education
of pet owners would lead to more responsible pet ownership, and while increasing education is a worthy goal that should be
pursued, gonadectomy of dogs and cats prior to adoption is one weapon in the fight against overpopulation that should be employed
at this time. Multiple studies have been published demonstrating safety of gonadectomy in puppies and kittens as young as
7 weeks of age. To that end, I recommend that all male and female dogs and cats should be spayed or castrated prior to adoption
from humane organizations.