**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** BOVINE RESPIRATORY DISEASE (BRD) IS A LEADING CAUSE OF MORBIDITY AND MORTALITY IN THE BEEF AND DAIRY INDUSTRIES. ECONOMIC COSTS TO THE CATTLE INDUSTRY DUE TO BRD HAVE BEEN ESTIMATED AS HIGH AS $3 BILLION ANNUALLY. PROPER NUTRITION PLAYS A CRITICAL ROLE IN MAINTAINING OPTIMAL HEALTH, AND HAS BEEN IDENTIFIED AS A KEY FACTOR AFFECTING THE INCIDENCE OF BRD. VITAMIN A (VA) IS A FAT-SOLUBLE VITAMIN THAT PLAYS A VITAL ROLE IN THE IMMUNE SYSTEM. ZINC (ZN) IS AN ESSENTIAL TRACE MINERAL THAT ALSO PLAYS A CRITICAL ROLE IN PROMOTING IMMUNITY. THESE TWO NUTRIENTS WORK TOGETHER IN MANY IMPORTANT ASPECTS OF GROWTH AND FUNCTIONING OF THE IMMUNE SYSTEM. STRESS AND DISEASE HAVE BEEN SHOWN TO ADVERSELY IMPACT THE WAY THE BODY ABSORBS AND USES VA AND ZN. CATTLE THAT ARE HIGH RISK FOR INFECTION ARE OFTEN FED HIGHER AMOUNTS OF VA AND ZN TO COUNTERACT THIS EFFECT; HOWEVER, THERE IS NO CLEAR EVIDENCE TO SHOW THAT THIS STRATEGY IS EFFECTIVE. FURTHER, IT IS NOT KNOWN HOW MUCH VA OR ZN A SICK ANIMAL NEEDS IN ORDER TO RECOVER FROM A RESPIRATORY INFECTION, WHILE MAINTAINING OPTIMUM GROWTH.THIS PROJECT WILL INVESTIGATE HOW VA AND ZN CONTRIBUTE TO OPTIMAL FUNCTION OF THE IMMUNE SYSTEM IN CATTLE WITH RESPIRATORY DISEASE. CATTLE WILL BE FED DIETS WITH VARYING CONCENTRATIONS OF VA AND/OR ZN TO DETERMINE HOW NUTRITION AFFECTS RESISTANCE TO A RESPIRATORY INFECTION. IT IS EXPECTED THAT ANIMALS RECEIVING OPTIMAL AMOUNTS OF VA AND ZN WILL BE MOST RESILIENT AGAINST RESPIRATORY DISEASE. THIS PROJECT WILL ALSO TEST A NEW APPROACH TO SUPPLEMENTINGVA AND ZNTO SICK CATTLE TOBE MORE EFFICIENT. THIS APPROACHIS INTENDED TO SPECIFICALLY 'FEED THE IMMUNE SYSTEM' OF AN ANIMAL THAT IS TRYING TO FIGHT OFF A RESPIRATORY INFECTION.THESE EXPERIMENTS WILL PROVIDE IMPORTANT INFORMATION ABOUT THE IMPACT OF VA AND ZN ON THE OUTCOME OF RESPIRATORY DISEASE IN FEEDLOT CATTLE, AND IN TURN, ON THE IMPACT OF RESPIRATORY INFECTIONS ON THE NUTRIENT REQUIREMENTS OF GROWING CATTLE. VITAMIN AND MINERAL PREMIXES ARE EXPENSIVE, AND THE INDISCRIMINATE USE OF HIGH-DOSE SUPPLEMENTATION IS A STRATEGY THAT MAY UNNECESSARILY INCREASE THIS COST. RECENT YEARS HAVE SHOWN A MOVEMENT TOWARDS PRECISION AGRICULTURE IN ANIMAL PRODUCTION. AT THE FOREFRONT OF THIS MOVEMENT IS THE FOCUS ON THE PERFORMANCE AND WELL-BEING OF EACHINDIVIDUAL ANIMAL,WITH THE GOAL OF MAXIMIZING ANIMAL PROFITABILITY. DEVELOPMENT OF A RATIONAL APPROACH TO NUTRITIONAL SUPPLEMENTATION, FOCUSING ON THEINDIVIDUAL ANIMAL WHICH IS MOST AT RISK FOR DISEASE AND NUTRITIONAL DEFICIENCIES, IS EXPECTED TO PROVIDE OPTIMUM BENEFIT TO THE ANIMAL AND TO MAXIMIZE PRODUCER PROFIT.