Sodium selenite is the inorganic compound with the formula Na₂SeO₃. This salt is a colourless solid. The pentahydrate Na₂SeO₃(H₂O)₅ is the most common water-soluble selenium compound.

Selenium is a essential element in almost all living organisms. Therefore it is widely used as a dietary supplement, both for human and animal consumption.

It is most commonly found in pet foods and animal feed. 

Often it is available in a 1% or 2% blended product. Find out more here