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Re: [RC] Vitamin E/Selenium supplements - Heidi Smith

>Good Morning:  Hoping someone has advice for muscle cramping issues.  My horse has had several incidences of mild cramping during training rides and this past weekend was pulled for lameness due to muscle cramping in the hind end.
>Several riders recommended supplementing him with Vit E/Selenium.
>I went to my feed mill and they do have a supplement there.  Label states Vitamin E 11,200 IU/LB.  Selenium 154 PPM
>Ok, since I'm math handicapped  :) - how do I figure out how much to feed?
Another poster already helped with the math.  Basically, the supplement has 4+ mg per oz, and likely was intended to be fed at the level of 1/4 to 1/2 oz per day, per FDA recommendations.  That doesn't even come close, if you are in a deficient area, but since this is a supplement of only E and Se, you can feed more if you have to without screwing up your other minerals.
Bravo to the vet who said that you need to supplement 3 mg per day.  That's more than most will recommend.  But according to Oregon State University, the horse's daily requirement is 8-10 mg per day, and having tested scores of horses over the years in central Oregon where our forage levels were purt-near zero, we had to supplement purt-near that whole amount to have blood levels in the normal range.  To supplement the entire amount, you'd have to feed 2 oz of the supplement. 
FWIW, the toxic level for chronic toxicity (meaning something you'd have to feed every day for awhile) is 60-90 mg per day--something you are only apt to achieve in the few tiny pockets of the country that have near-toxic levels in the soil. 
As for blood testing--you can draw blood yourself and send it in--and the lab fee at Michigan State University's diagnostic lab is somewhere between $20 and $30.  And personally, I wouldn't send a selenium assay to just any old lab, as most don't do that many of them.  Also beware the "normal" ranges published by labs who don't do a lot--many suggest that the "normal" range is around 160 ppb to 190 ppb, but more recent work suggests normal is 200 to 250 ppb, and that we've been looking at borderline deficiencies all along because they are "average." 
Horses DO have a considerable difference between individuals in how deficient they will be, given a marginal to deficient selenium level in the diet--some are much more able to absorb it than others, apparently.
As for testing before supplementation--if you live in a known selenium deficient area, I wouldn't hesitate to supplement accordingly, even without testing.  ALL commercial feeds are "selenium deficit" feeds--ie, you need a selenium density of about 0.9 to 1 ppm average in all your feeds for the diet to have enough in it.  Senior feeds run 0.3 ppm.  Some "high" selenium feeds run 0.6-0.7 ppm.  So unless your forage has oodles in it, you can safely supplement.  (Your ag extension agent can give you a pretty good idea what your forage is apt to run in your area.)
As I previously mentioned, in central Oregon I didn't hesitate to supplement the entire daily requirement--8 mg per day.  Here in central Idaho, I supplement about half or more of the daily requirement to the actively working endurance horses, and give it to the broodmares by injection, since they don't get a daily concentrate.  (Our forages here are pretty good on other stuff.)

[RC] Vitamin E/Selenium supplements, Joslyn Seefeldt