Selenomethionine as a safer substitute for barium selenate in long-acting injectable Se supplements for food-producing animals

Supplementation with injectable selenium (Se) can treat and prevent Se deficiency in livestock. Among commercially available formulations, barium selenate (BaSeO4) is preferred because of its long-acting slow-release efficacy. When administered to food-producing animals however, it can become a health risk to humans if the concentrated depot of an injection site is consumed. Such use of BaSeO4 is now restricted in the EU. Selenomethionine (SeMet), a naturally occurring form of Se, is a possible replacement for BaSeO4 in long acting injections. In a series of proof of concept studies we showed that injection with SeMet can increase and maintain nutritionally adequate Se concentrations in the blood and tissues of young lambs in grazing flocks for at least 191 days, and in cattle for at least 95 days. Stereoisomer forms L- and DL-SeMet were found to be functionally equivalent. Further studies are needed to evaluate the safety and efficacy of long-acting SeMet injections in terms of animal performance responses when administered to Se-deficient livestock that are managed under various husbandry systems.