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RE: [RC] where is selenium high/low? - Susan E. Garlinghouse, DVM

This brings up a really good point.  We ran into a lot of horses in central
Oregon with levels really "bottomed out" that >absolutely WOULD NOT increase
their levels even being fed fairly high levels of supplemental selenium.
The selenium yeast >was not available then, so the injectable was really the
only method we had to get the selenium actually into the blood <stream.
Once we GOT these horses to an acceptable whole blood level, they seemed to
MAINTAIN just fine on oral products.>

I suspect that this is the same thing that Susan is seeing, but she is
using a more bioavailable oral product that can't be >so easily just shunted
on down the GI tract and into the manure pile.  Even so, I gather that she
is having to hammer these >horses pretty hard to get the levels up to par in
the first place.

Another factor that probably played into it was that while the PNW is
notoriously low in selenium, So Cal has traditionally been thought of as
being 'adequate' in selenium, and horses weren't often even evaluated or
treated for deficiencies.  Even less so given that the published 'normal'
range for Se values is considerably lower than what seems to be optimal for
many horses.

Given those regional differences, that might be why I rarely have to use
injectable selenium to start to get some response from oral dosing, and
never had to more than twice in one horse (and the really interesting thing
is that that one stubborn horse had originally come down from the Klamath
area, virtually on the borders of Oregon).  Even when we had deficiency
issues, the horses probably never get to the same extremely low levels you'd
be likely to see in the PNW, FL and some of the Great Lakes and other
extremely deficient regions.

I have no scientific proof of this hypothesis, but I always believed (given
the known role of selenium as a cofactor in >enzyme functions in cell
membranes) that the selenium-deficient cells of the lining of the GI tract
were incapable of taking >up the very selenium that they needed, but once
they had some on board, they worked just fine at getting it out of the gut.

That sounds like a reasonable hypothesis to me.  We know there are other
failures in GI uptake when the system is starved of that substrate, thus
many of the developments in parenteral nutrition under extreme conditions.

Susan Garlinghouse, DVM


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RE: [RC] where is selenium high/low?, heidi