From:
Brett Middleton
Date: 2001-03-30 17:25:00 UTC
Subject: Re: Dr. Williams - Experience begets Understanding?
"Bruce Williams, DVM" <williams@e...> wrote:
> The only way to generate valid data of this type would be to split a
> colony of ferrets in half - neuter 50% early, 50% late, and see what
> happens over a lifetime.
Wouldn't it be even better to split the late neuters into two groups,
doing some prepuberal and some postpuberal?
> Once again, not economically feasible.
An excellent point, given what's happened to research funding. It
seems like you can't get a grant unless you're doing applied science
that's so far back from the frontiers of knowledge that you can
guarantee success, and promise that somebody will make millions off the
results within two years. Yet, at the same time we're talking about a
problem that is definitely of economic importance, so there ought to be
a way to shake out the money *somewhere*. The problem seems to be that
the economic impact is on the consumer (pet owner), rather than the
producer, and it's hard to get enough of us organized to guarantee the
necessary level of funding. If there was an economic feedback hitting
the producers in the wallet, I'd bet funding would materialize PDQ.
Which makes me hope that veterinary medical insurance for ferrets
becomes *really* popular, because the insurance company would then have
the bucks to get this done, and a serious economic incentive to fund
research that would reduce their payout. (Or, they could simply refuse
to insure farm ferrets, which would give the farms incentive to solve
the problem, assuming that few people would want to buy an uninsurable
fuzzy. B-)
> My personal belief is that it is genetically bred into the American
> ferrets, which started with a relatively small gene pool producing
> the vast majority of animals for the pet trade.
I'm still not convinced that we know any such thing about the size of
the initial gene pool, despite what our intuition tells us. And our
experience in establishing various breeds of livestock here seems to
show that we can produce large populations of healthy animals starting
from surprisingly restricted gene pools. (Though admittedly we don't
know just how much secret crossbreeding was going on behind closed barn
doors. B-)
It's a shame that we've got such good information on livestock
importations going back to colonial days, but don't seem to have
anything equivalent for companion animals. But, it seems likely to me
that there must have been a number of early ferret importations from
different sources, and that the various current-day farms would have
been drawing from somewhat different pools before closing their
bloodlines. That makes it a little hard to believe that they all got
the same jokers in their genetic woodpiles, while small closed
populations such as Australia did not.
> We also have a very high incidence of other diseases, such as
> cardiomyopathy in American bloodlines.
Again, do we really have a reasonable degree of certainty that there
*is* a true difference in the incidence rate of these diseases, or are
there simply differences in detection and reporting because of
husbandry practices? Is it possible that American house fuzzies are
simply observed more closely, that we are more alert to these diseases,
and/or that we're more indulgent to our pets and thus more likely to
seek veterinary care for every sneeze and sniffle?
> Other people may point to dietary influences, the influence of
> photoperiod, etc., but a genetic background appears to be the most
> able to explain the tremendous differences in ferquency between
> American and non-American bloodlines.
I would agree that genetic effects are likely to be significant, but
I'm not ready to say they're *most* significant. After all, we
consider a trait to be highly heritable if additive genetic variation
explains only 30-40% of the phenotypic variation, leaving 60-70% to be
explained by environmental causes. And *that* occurs ONLY among groups
of animals born in the same year/season, in the same herd, and managed
alike. When you look at variation *across* herds, the genetic portion
drops precipitously.
Given that there are genetic differences among countries, those
differences are presently almost totally confounded with management
effects. Someone else suggested that the rising incidence of
"American" diseases in Sweden may be due to the importation of American
bloodlines. But that certainly couldn't be the cause of the rising
incidence in Australia, since that population has been closed for
decades. The only thing that *both* countries are likely to be
importing from the US is our style of husbandry. Their ferrets are
increasingly being moved indoors and switched to commercial pet foods.
I don't know if we'll ever get the data to sort this all out, but it
sure is a fun problem! B-)
Brett
*SLMW 1.0* "Back off man, I'm a scientist!" -- P Venkman, PhD