Modern animal production is associated with high animal performance. This is of course beneficial in terms of profit, but it also comes at the cost of a compromised health and increased level of stress (for example caused by high stocking densities), which in turn both negatively affect performance. Therefore, it is very important to reduce stress and optimize the health status of animals.

Selenium is important in the synthesis of selenoenzymes, such as glutathione peroxidase, which reduce the reactive oxygen species (ROS) that are often increased during stress. The incorporation in functional enzymes allows selenium to reduce stress and provide the animals with a better antioxidant status. Since the demand for selenium is increased during times of challenge, a safe deposit of selenium inside animal tissue can allow for a continuous selenium supply.

Such a safe deposit of stored selenium can be achieved by supplementing the feed with L-selenomethionine, the only form of selenium that can be stored in animal proteins. The effects of L-selenomethionine on stress, health and antioxidant status has been shown in several species such as in aquaculture, equine, pigs, poultry and ruminants.