Triennial Growth Symposium--Novel roles for vitamin D in animal immunity and health.

Recent years have seen significant advances in the generation, validation, and implementation of nutritional supplements for food production animals. Examination of their impact on animal performance and health requires collaboration among animal scientists, nutritionists, biochemists, immunologists, veterinarians, and others. Each provides a unique perspective on the mechanisms of action, short and long-term impacts, and most effective strategies for implementation into continuously evolving industrial practices. In this review we provide a comparative immunology perspective on the impact of vitamin D on animal performance and health, describe the differential contributions of vitamin D3 and of a commercial hydroxylated version of vitamin D3, 25-hydroxyvitamin D3 (25(OH)D3 or HyD) to swine immunity, and highlight recent advances in the technologies that can be used to dissect the cellular and molecular mechanisms that impact production animal immunity and health. Among others, we pay particular attention to how these novel approaches help decrease the variability often observed in immune-associated datasets. From a practical perspective, this is critical for evaluation of in vivo effects for this nutritional supplement as small but meaningful changes to specific immune responses are typical under normal physiological conditions. Furthermore, as the range of reagents and technologies expands for comparative animal models, it is imperative that continued efforts are placed on the capacity to compare results across different experimental platforms.