206 Beyond NRC Requirements: The Role of Non-nutritives in Equine Health and Performance

Abstract Billions of dollars are spent annually on dietary supplements, with similarities between products consumed by humans and those offered to horses and other animals. Dietary supplements encompass a variety of substances, some non-nutritive and others recognized as essential nutrients, but all are fed with the intent of providing a health or performance benefit beyond that supported by the normal diet. Though many of these products are sold without sufficient evidence of efficacy, their increasing popularity has driven horse owner curiosity and researcher interest. Over the past two decades, funding for research on dietary supplements in horses has exceeded that spent addressing knowledge gaps in the nutrient requirements of horses. Many of these substances are difficult to study (e.g., herbs, botanical extracts), due to their complex composition, unidentifiable active compounds, or broad biological effects that are difficult to characterize. Others have shown promise for reducing inflammation and improving immunocompetence, including various fatty acids, probiotics, prebiotic fibers, and antioxidants. Among these are well-known nutrients that are either being fed above current requirements (e.g., vitamins, minerals), or are presumed to be essential but requirements have not been established for the horse (e.g., essential fatty acids, amino acids, vitamins). In most cases, the benefits are not realized in an already healthy horse but are instead demonstrable in animals under high stress conditions (e.g., intense exercise, transport) or states of immunocompromise (e.g., inflammatory disease, senior horses, foals). Should dietary supplements be included in discussions of nutrient requirements and a future revision of the horse NRC publication? When does a compound become a nutrient – or a drug? Could there be a situational requirement for a dietary supplement if it returns the animal to homeostasis when the regular diet does not? This presentation will provide fodder for a group discussion on future directions of equine nutrition.