Selenium Supplementation in Exercising Horses

Selenium plays many important roles in a horse’s body, one of which involves fighting off damaging free radicals produced during exercise. The mitochondrion—also known as the powerhouse of the cell—is a prodigious producer of free radicals during exercise. Trainers attempt to ward off free radicals by supplementing diets with selenium. Unfortunately, this strategy may negatively impact the mitochondrion’s ability to respond and adapt to exercise for maximal energy production to fuel working muscles.

To determine the effect of selenium on the mitochondrion’s ability to adapt to athletic training, one research team* recruited 30 Quarter Horse yearlings. The horses were divided into two groups, a training and a nonexercised group. Within each of those groups, horses were supplemented with either 0.1 or 0.3 selenium mg/kg dry matter (DM). After 14 weeks, horses underwent submaximal exercise tests and researchers evaluated mitochondrial function.

“The National Research Council currently recommends 0.1 mg/kg DM of selenium daily; however, optimal dietary selenium during periods of high demand, such as training, remain unclear and could, in fact, be higher,” explained Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research (KER).

Nonexercised horses receiving 0.3 mg selenium/kg DM had higher citrate synthase activity—a measure of mitochondrial mass (the amount of energy-producing mitochondria in muscle)—than horses receiving only 0.1 mg selenium/kg DM. Further, when horses were originally supplemented with 0.3 mg selenium/kg DM then offered only 0.1 mg selenium/kg DM, a significant decrease in mitochondrial activity occurred (measured via the activity level of the cytochrome c oxidase enzyme), suggestive of impaired mitochondrial function.

These findings prompted the researchers to suggest the following:

In addition to the antioxidant benefits of selenium, supplementation with selenium may also improve mitochondrial biogenesis, an increase in mitochondrial mass to improve energy production;
The reported improvements in mitochondrial density (as evidence by increased citrate synthase activity) in response to dietary selenium supplementation may improve diets for elite equine athletes; and
It may not be prudent to decrease dietary selenium during an exercise training program to preserve mitochondrial function during exercise.
“This is a fascinating study because it provides some proof that the National Research Council recommended levels are minimal and perhaps not optimal like nutritionists have speculated. That said, owners need to appreciate that selenium has a narrow range of toxicity. Selenium supplementation should not exceed 2 mg/kg DM intake, which equates to approximately 20 mg selenium in the total diet for a 1,100-lb (500-kg) horse,” shared Crandell.

Looking for an effective antioxidant supplement to help support your working horse’s mitochondria for maximal energy? Preserve PS fits the bill.

“Preserve PS is a powdered supplement containing a blend of powerful antioxidants, including selenium and vitamin E to help exercising horses ward off the damaging effects of free radicals,” Crandell relayed. “Preserve PS contains 2 mg of selenium per 30 g serving, as well as 1,500 IU of vitamin E.”