Q: "Crap Bob...if ferrets need sunlight to make vitamin d and if
ferrets are prone to getting sick from too much vitamin d, what are
we supposed to do? What are your wise thought?"

A: Sorry, I have a wise ass, but no wise thoughts. Wait, I have one:
"Those that can, do. Those that can't do, teach. Those that can't
teach, warn." Sorry, that is all I have the Yoda-Bob archive.

I am actually covering this subject in great detail in the diet posts
I'll be starting in a few weeks, so I don't want to spend a lot of time
on it here. In a very basic sense, ferrets have some potential problems
with vitamin D, but since there is little published research, any
viewpoint is somewhat conjectural -- regardless of the alphabet soup
after your name. I do wonder if having "PhD" after your name makes your
"I don't know" somehow better.

Indoor ferrets probably don't get enough pure sunlight. Vitamin D is
created in the skin by an interaction of the UV component of sunlight,
cholesterol, and a few other things. The skin reaction is generally
self-limiting and does not result in toxic levels of the nutrient. I am
of the opinion that if a ferret's body can do things naturally, there
is no reason to supplement them. Thus, I allow veterinarians -- not
sage advisers, nor even nutritionists -- to determine true cases of
vitamin D deficiencies based on blood serum levels, and prescribe the
appropriate remedies. In some states, that actually may be the law. ;-)

In some strict carnivores, such as cats, vitamin D is poorly
synthesized in the skin, and nutrient requirements are met when the cat
eats whole prey. Research in ferrets has not yet placed ferrets in the
same category as cats in this regard. Nonetheless, if I was a 'warner',
I might say it would be prudent to place ferrets on a whole carcass
diet to insure an "evolutionary proper" amount of vitamin D in their
food.

Since most cat species are strictly nocturnal, and most polecats are
crepuscular, I would postulate cats lost their ability to use sunlight
to synthesize vitamin D through random chance, and since they had a
ready supply of the vitamin in the bodies of prey, it didn't matter.
The more crepuscular polecat could have gone through the same process,
but if so, someone needs to provide some evidence that supports the
idea. Until then, since giving a ferret sunlight will not hurt them,
and since it could actually help them by providing them with an
important nutrient, I say, "Damn the torpedoes...full steam ahead!"
It is a win-win situation.

It is important to note that UV light is required to make vitamin D in
the skin. UV is a normal component of sunlight. If the glass in your
windows filters UV light, your ferret can sun all they like and it will
not help them make vitamin D (assuming they can, which I don't think
is a bad assumption without contrary empirical data). A lot of modern
windows filter UV, so again, it helps to take your ferrets outside and
let them sun as much as they like. If you don't know if your window
filters UV, assume it does.

There is another problem with ferrets and vitamin D. Vitamin D is
fat-soluble. If you eat a lot of fat, the lipids in the poo can hang on
to the vitamin D and shoot it out the back end. This is especially true
when there are fast bowel transit times present and fiber in the diet
is low. Ferrets are unique in that they have a lot of "risk" factors
for low vitamin D. This could a serious problem in those animals fed
kibble, because the vitamin D supplement is added to the oils that are
sprayed on the surface of the kibble after extruding. If the oils that
contain the vitamin D are not digested and are eliminated, there is a
good possibility that much of the vitamin D rides out with them. This
problem can be worsened by giving other supplements at the same time,
such as vitamin A. Giving something like cod liver oil could make the
situation worse because it is so effective in transporting vitamin D;
it has been implicated in stripping fat-soluble nutrients from foods
traveling down the gastrointestinal highway.

Another thing to consider is that bile from the gallbladder is required
to properly absorb fats. Fats don't like water, so without bile they
clump up into large droplets and tend to shoot out the other end. Bile
emulsifies fats, meaning it makes the fat drops in the food bolus
smaller and helps in getting them out of the intestine and into the
body. Some very interesting European research shows a lot of ferrets
have gall bladder disease. I watched a vet remove diseased gall
bladders from ferrets, open them up, and looked at the stones. It is
very possible that ferrets with gall bladder disease could have a
problem getting enough vitamin D.

It should be interesting to note that polecats don't seem to have these
problems. How do I know? Because I study their skeletons and I know how
to recognize osteoporosis. Since vitamin D is a necessary nutrient for
good bone health, animals with healthy bones probably do not have a
problem ingesting or synthesizing the nutrient. Since my studies are
showing wild polecats, feral ferrets, and ferrets kept out of doors
and fed an evolutionary diet have very dense bones, regardless of
other dietary issues, we know they are meeting their minimum vitamin D
requirements. Bone loss doesn't mean they have a vitamin D problem, but
healthy bones generally means they don't.

This is just the tip of the vitamin iceberg. Wait for the diet posts
I'll be sending in soon. Unfortunately, I'll be on the road for the
next 2 weeks, so I can't respond to future replies to this post until I
get back. Now is your chance to get at me while my back is turned. ;-)

Bob C
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[Posted in FML 5554]