At 02:59 PM Tuesday 7/19/2005, jana lashmit wrote:
>   I think a lot of vets go by what they have witnessed directly.  One of
> the vets I work for has been in practice 40 years, he prefers that the
> females have at least one heat and the males fully grown (varies by
> breed).  He believes that waiting longer decreases the chances of
> obesity, joint problems, cruciate ruptures, as well as incontinence, and
> blockages in male cats.  Our new vet, fresh from school, firmly believes
> that earlier is better.

Sounds like your older vet has been really observant.    It's not
necessarily easy to spot these trends.

ALL of the things your older vet mentioned as adverse effects of
spay/neuter in dogs are documented in the veterinary medical
literature.  Not only as individual preferences, but as statistically
significant findings when whole populations of intact and s/n dogs were
compared.  Few of these studies, however, actually looked into whether
delaying spay/neuter has an impact.. most looked only at intact and
spay/neutered populations without regard for age at s/n.  Your vet may be
entirely right that these things are mostly issues if the dog is s/n before
maturity.  For some things, we know this is true.

There was a study that found that osteosarcoma is twice as likely in s/n
dogs than in intact dogs.  A later study looked into this as a function of
age at s/n.  Turns out it was only dogs s/n before 12 mo. of age who had
the statistically significant increase in osteosarcoma... for them it was
3-4 times more likely than dogs left intact.  For the population of dogs
s/n after 12 mo., they were no more likely to develop osteosarcoma than
intact dogs.  Incidentally, I suspect this may tie in with the known fact
(shown in studies) that s/n before the growth plates in the bones close
causes the bones to continue growing for a much longer period of time.   If
so, 12 mo. isn't the magic number, it's whenever the growth plates close,
which may be a bit later than 12 mo.  For farmcollie sized dogs, my vet
says that the growth plates will not all be closed by 12 mo. of age, but
will be by 24 mo. of age (not sure exactly when in between 12-24 mo it
occurs).  This hormonal impact on bone growth may tie in with joint
problems too.

Laura Sanborn