Selenium

Selenium (Se) is an essential constituent of certain antioxidant enzymes through which it helps to combat free radicals. It also has a stimulatory effect on immunity and therefore helps generally in the body’s defence reactions.

Se is a trace element that is essential in small amounts, but is toxic at high doses. Se plays an important role in antioxidant defense and immune function in horses.

The levels and chemical forms of Se vary according to the composition and Se content of soil in which the plants are grown.

Selenium supplements are available in several forms. Sodium selenite and sodium selenate are inorganic forms of selenium. Sodium selenate is almost completely absorbed, but a significant amount is excreted in the urine before it can be incorporated into proteins. Sodium selenite is only about 50% absorbed but is better retained than selenate once it is absorbed.

Chronic selenium toxicity (selenosis) may occur with smaller doses of selenium over long periods of time.