THE BIOLOGICAL ROLES OF SELENIUM AND VITAMIN E IN LIVESTOCK: IMPLICATIONS FOR GROWTH, IMMUNITY, REPRODUCTION, AND ANIMAL WELFARE

ZOOLOGY

Selenium and vitamin E are essential micronutrients that play critical roles in maintaining health, productivity, and physiological balance in livestock. Although required in small quantities, these nutrients regulate vital biological processes, including antioxidant defense, immune function, reproduction, growth, and stress adaptation. Selenium functions primarily through incorporation into selenoproteins, such as glutathione peroxidases and thioredoxin reductases, which protect cells against oxidative damage and maintain redox homeostasis. Vitamin E acts as a lipid-soluble antioxidant that prevents membrane lipid peroxidation and preserves cellular integrity. The synergistic interaction between selenium and vitamin E enhances antioxidant capacity and improves resilience against oxidative stress caused by intensive production, environmental challenges, and disease conditions. This review highlights the biological functions of selenium and vitamin E in livestock, with emphasis on their effects on growth performance, feed efficiency, meat and milk quality, immune modulation, disease resistance, reproductive efficiency, and animal welfare. Adequate supplementation of these micronutrients has been associated with improved antioxidant status, enhanced immune responses, better reproductive outcomes, and increased tolerance to stressors such as heat stress and transportation. Conversely, deficiencies can lead to disorders including nutritional myopathy, reduced productivity, reproductive problems, and increased susceptibility to infections. The review also discusses dietary sources, bioavailability, deficiency causes, and supplementation strategies for optimizing selenium and vitamin E status in livestock. Understanding the physiological and molecular roles of these nutrients provides valuable insights into their application as functional components of sustainable livestock production systems aimed at improving animal health, productivity, and welfare.

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