Innovative Selenium Research

LogoKelsey Johnson Nonella, Ph.D certified equine nutritionist for Horse Guard Supplements.

“It takes the body a long time to recover from a selenium depletion, and this

study emphasizes the importance of continuous organic selenium

supplementation of 0.3 ppm.” – Dr. Kelsey Johnson Nonella

September 2014


In search of more knowledge of selenium, an essential trace mineral that is extremely deficient in the northwest, Horse Guard funded an extensive research trial at West Texas A&M University. The study took ten Quarter Horse geldings through a 4-month selenium depletion period and 4-month selenium repletion period, during which they were fed a grass hay grown in the Northwest. We monitored whole blood selenium concentrations monthly.


The depletion diets provided only 7.6% of selenium that weiStock_000000093736Small, at Horse Guard, recommend. All of the horses had normal blood selenium before the start of the trial.  After 56 days, the horses’ whole blood selenium concentrations (136 ng Se/ mL whole blood) indicated that the horses were sub-clinically deficient in selenium.To gain more knowledge about the effects of selenium deficiency on horses in the Northwest, we kept the horses on the selenium-deficient diet for two more months. At the end of depletion, the horses’ whole blood selenium concentrations averaged 109 ng Se/ mL whole blood, which is considered sub-clinically deficient. With the less severe deficiency (sub-clinical) the horse has lowered immunity, decreased muscle function, lower conception rates and other maladies that cannot be seen with simple observation. 


After being fed the deficiGrazing_Smallent diet for 4 months, the horses were then put on a repletion diet for 4 months (the selenium repletion phase). They were fed the same deficient hay and Horse Guard, containing two different levels of selenium.  One group was fed  0.1 ppm (the level of most supplements) or 0.3 ppm organic selenium (the level in Horse Guard Products).  The horses consuming 0.3 ppm organic selenium supplementation increased more rapidly and had significantly greater whole blood selenium concentrations by day 28 as compared to horses supplemented with 0.1 ppm organic selenium, and continued to have higher values throughout the rest of the trial. It is very important to note that after 4 months of organic selenium supplementation after being depleted, with a hay grown in the Northwest, that the horses’ whole blood selenium concentrations did not reach levels that are considered adequate.


This information indicates that it takes the body a long time to recover from a selenium depletion, and this study emphasizes the importance of continuous organic selenium supplementation of 0.3 ppm.  This university research is validation that Horse Guard Products provide the critical levels of organic selenium for optimum health.

– Dr. Kelsey Johnson Nonella Ph.D. P.A.S, Equine Nutritionist at Horse Guard Inc.

About Dr. Kelsey J. Nonella Ph.D., P.A.S.

Kelsey J. Nonella, Ph.D. is an equine nutritionist who was riding horses before she could walk. Her love for horses drives her to help educate people on what their horses’ needs in order to have happy, healthy horses. Kelsey went to Cal Poly receiving a Bachelor’s of Science in Animal Science and then onto West Texas A&M, where she got her Masters and eventually her Doctorates in Equine Science. At A&M, Dr. Nonella did extensive research on Selenium within horses. Click here to view her research. Kelsey’s colleagues have mentioned her as one of the United States equine Selenium experts.
View all posts by Dr. Kelsey J. Nonella Ph.D., P.A.S.

4 Responses to “Innovative Selenium Research”

  1. Dave Albin says:

    It’s interesting that you didn’t make it back up to where you started, and that the repletion lines have plateaued. Does this have long-term health consequences? I suppose that’s the next logical question after this data here. Would it be possible to increase Se bioavailability from feeds by extrusion or processing?

    • mm Dr. Kelsey Johnson Nonella says:

      So sorry for the late response. You bring up a good question. The horses being fed a diet that has adequate selenium will eventually reach adequate whole blood selenium concentrations as seen in other research trials. Looking back I wish that I could have kept supplementing these horses until they reach adequate selenium levels and monitored how long it took. Unfortunately, the depletion and repletion periods had been predetermined when writing the grant proposal. Processing feeds such as soybeans and oats can make the selenium more available to the horses. However, in this situation the concentrated selenium yeast was used in a pelleted product. Thank you for the comment.

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