It sits in the reticulum, the front part of the rumen, and slowly releases selenium. It does not dissolve and causes no harm to the animal. It resides there much as a magnet does when given.

The bolus is designed to be given with a standard balling gun. No special equipment is needed.

Selenium deficiency can cause weight loss, diarrhea, poor weight gains, retained placenta, abortions, infertility, poor response to vaccines, white muscle disease, light hair coat, decreased immune response and decreased resistance to disease.

Selenium deficiency is the most commonly diagnosed beef cattle health problem in California. A simple blood sample can be used for analysis to determine if an animal or a herd is normal, deficient or marginal.