Re: RC: Re: Selenium problem

[CMKSAGEHIL@aol.com]

In a message dated 2/10/00 1:03:41 PM Pacific Standard Time, 
mmieske@netonecom.net writes:

<< I have been told that 20 mg./daily over a prolonged period of time can
 actually cause SE toxicity and I have also read that TOO MUCH SE can
 actually show up in blood tests as a DEFICIENCY...I believe I read this a
 couple of years ago on a list in England. In fact, if I remember correctly,
 the lady who posted her story had gone so far as to give her horse SE shot
 after SE shot and in effect killed her horse by overdoing it.  >>

Numbers I got from Oregon State University several years ago for chronic 
toxicity were 60-90 mg per day.  Of course, this was the TOTAL intake--I can 
certainly see 20 mg of supplementation daily causing a problem if the feed is 
already quite high.

We did deal with a toxic horse when I was in vet school--this was back in the 
'70's.  Someone had heard that "selenium is good for endurance horses" and 
was giving weekly E-Se injections as well as feeding an oral supplement, 
while residing in an area of Nevada that already had overly high levels in 
the soil (and hence in the pasture grasses and local hay).

I'm not familiar with the concept of overloads causing lowered blood 
levels--did deal with one cow who had come from an overly abundant area that 
had blood levels around 900 ppb and showed no clinical effect.  (Normal for 
cows is the same as for horses--around 200 to 250 ppb.)

It has been our clinical experience that many severely deficient horses will 
apparently not absorb sufficient selenium to meet their needs until the 
levels are raised by injection first.  I don't know the exact mechanism of 
this, but I strongly suspect that it has something to do with abnormal cell 
membrane function in the GI tract, since selenium is a vital factor in cell 
membrane function in everything else from muscles to white blood cells.

Heidi