Comparing organic selenium sources

There is a growing interest in using selenium-based products as an antioxidant, not only for breeding stock but also for commercial animals. A wide range of products is available. The question is how to select the most efficient one. Chemical analysis does not appear to be sufficient to fully appreciate the bioavailability of the large range of dietary sources of selenium (Se) available for animal feed. Tissue selenium deposition is a reliable criterion to evaluate the bio-efficacy of various selenium sources. A wide range of products is available, from inorganic, sodium selenite or selenate coated or not and nanoparticles to organic forms such as selenised yeasts, chelates of selenomethionine (SeMet), pure forms of SeMet or hydroxy-selenomethionine (HMSeBA) and some complex sources of selenium based on mixing mineral selenium with glycinates, proteinates etc. It has been confirmed that, compared with mineral selenium, its organic forms are better absorbed and therefore serve selenium needs more effectively. Research has revealed that selenium incorporated as selenocysteine (SeCys) is the key amino acid (AA) supporting the antioxidant properties of most of the 25 selenoproteins identified in animal species or humans, such as glutathione peroxidase, thioredoxin reductase and methionine sulfoxide reductase. However, this SeCys has to be synthetised de novo by the cells and cannot be supplied through feeds. Dietary SeCys undergoes complete transformation to selenide (H2Se) to synthesise de novo SeCys.