The team ultimately concluded that horses might benefit from greater amounts of selenium in the diet compared to NRC recommendations to increase glutathione peroxidase activity. | Photo: Photos.com

Selenium (Se) plays an integral role in many of the equine body’s functions, including production of the enzyme glutathione peroxidase, an antioxidant that’s vital in preventing and repairing oxidative damage to cells. In horses residing and grazing in selenium-deficient geographic areas (including the Pacific Northwest, Great Lakes, and New England regions of the United States), this antioxidant capacity could be compromised if owners don’t provide selenium supplementation. Impaired immunity, elevated blood levels of muscle enzymes, and tying up have all been reported in horses with selenium deficiencies.

In the recent UK study, which took place over 18 months, Mieke Brummer, PhD; Laurie Lawrence, PhD; and colleagues randomly assigned 28 pasture-kept horses (eight mature geldings and 20 nonpregnant, mature mares) to one of four treatment groups: low selenium (LS), adequate selenium (AS), high organic selenium (SP), or high inorganic selenium (SS). The AS horses served as controls, and the researchers maintained them on a diet formulated to provide 120% of National Research Council (NRC)-recommended dietary selenium intake throughout the study.

To deplete horses’ selenium stores, the other three treatment groups consumed a diet consisting of 60% of the NRC’s recommended selenium intake for the first 196 days. Blood samples taken during this period confirmed that horses’ selenium stores had been depleted