The Role of Selenium in Sheep Health

Abstract Selenium (Se) is an essential mineral for animal health. Due to widespread soil Se deficiency in global regions, selenium must be supplemented in sheep diets to prevent harmful conditions such as white muscle disease (WMD). Previous research has also demonstrated the beneficial immunomodulatory properties of Se in improving antibody production and reducing inflammation. Beyond its role in disease prevention and immunomodulation, Se functions as a potent antioxidant, promotes thyroid hormone metabolism, and improves reproductive outcomes. Strategies for improving animal Se status can include adding Se to mineral premixes, salt blocks and feed additives, enriching crops with soil Se, and even Se injections. Se primarily comes in either organic or inorganic forms. Though organic Se is more bioavailable, it is costlier than inorganic Se. This case study evaluates the impact of organic versus inorganic Se supplementation on ewe Se status and immunocompetence in 110 Dorset-Rideau ewes during the late pregnancy and lactation periods. The sheep were located in Ponsonby, Ontario, Canada. Though immunocompetence was not significantly different between treatment groups, the ewes in the organic treatment groups had higher serum Se concentrations after trial day 40, showing the benefit of organic Se in improving Se status over time. Information © The Authors 2025