Selenium Help

["G & J Thom" <thomlabs@netbistro.com>]

Since we are on the topic of Selenium.  I bought a mineral
my vet recommended.  
Here is what is in it:   Sel  30mg/kg
                                Calcium  17%
                                Phos       17%
                                Fluorine    1700mg
                                Cobalt          35mg
                                Copper      2300mg
                                Iodine          100mg
                                Manganese  6500mg
                                Zinc             5900mg
This is a 55lb bag.  I noticed there is no Vit E and listening
to everyone it should be fed with the selenium.
Was wondering how much of this mineral I should be feeding?
Or does anything think I should find a different mineral?
I have a mare that is deficient in Sel and Calcium and she is in
foal.

Thanks for any help
Julia