Selenium (Se) is an essential trace element in animal nutrition, and exerts multiple actions
related to animal production, fertility and disease prevention. Glutathione peroxidase (GSHPX) enzyme was the first proven selenoenzyme that can prevent oxidative damage of the
cellular membrane. Actually more than 30 selenoenzymes have been described and a hierarchy process for expression in the animal has been established. White muscle disease
(WMD) was the first recognized condition associated with Se deficiency. WMD causes new
born mortality, especially in ruminants, and impaired production condition in growing and
adult animals. Selenium is critical to thyroid hormone synthesis and it is also very important for converting T4 (thyroxin inactive form) to T3 (active form). A good immune response
requires Se too. Selenium status in soil, plants and animal blood and tissue can be used in
the diagnosis of Se deficiency. Diverse forms of Se supplements are available, but many
factors affect their activity and efficacy, such as its chemical form and animal’s health and
production condition. The relationships between foetus Se metabolism and pregnant dam
Se status are critical for productivity and need further research