“How much Selenium is in Horse Guard and why?”
Answer from Equine Nutritionist, Del Johnson:
All of our multi-vitamin/mineral products provide 3 mg. of organic selenium to a 1000 lb horse. Horse Guard provides it in a 2 ounce dose.
Nutritional recommendations vary greatly no matter the element to which they refer. Most nutritionists are not from a selenium deficient area and know little about the deficiency. We were the first company to provide an oral equine supplement for selenium in 1978. Selenium research was started at Oregon State University. Before that research there was no recommendation for selenium. Dr. Stowe at the Michigan State University did original work with selenium in equines. His work included horses that were not being used or stressed. The NRC recommendations that followed were for 1 mg per day for a 1000 lb horse. After that time most recommendations by nutritionist were for 1 mg per day.
Research in the early eighties showed that baby pigs under stress of weaning did much better on a diet of .3 ppm selenium. As a result of testing horses we began recommending a higher level of selenium for horses under stress at 3 mg per day. As you know horses are typically under much more stress than farm production animals.
Nutritional science really does not know enough about selenium metabolism. As a result we are currently funding a selenium study at West Texas A&M. This work is being done by my daughter who is completing her PhD work. The study takes selenium sufficient horses and puts them on a selenium deficient diet with hay from Central Oregon.
We monitor the depletion of selenium in the blood over time. That phase is complete. All of the horses were significantly deficient at day 112.
We are currently in repletion phase and are now monitoring the repletion by adding organic selenium to the diet with Horse Guard.
The recommendation for Horse Guard is 1 ounce per 500 lbs body weight. That provides 2 ounces of Horse Guard per 1000 lbs. Two ounces of Horse Guard provides 3 mg of organic selenium per 1000 lb horse per day. The toxic level of selenium is above 20 mg per day. You would have to feed almost 8 times the recommended dose of Horse Guard each day to reach toxicity.
I hope this helps. I apologize for the length of the response but we take great pride in our leadership in equine nutrition especially when it comes to selenium.