ZINC IS A TRACE MINERAL REQUIRED BY ANIMALS AND PLAYS AN IMPORTANT ROLE IN MANY BIOLOGICAL PROCESSES THAT SUPPORT HEALTH AND GROWTH. INCREASING ZINC BEYOND DOCUMENTED REQUIREMENTS IN RAPIDLY GROWING CATTLE CAN FURTHER IMPROVE GROWTH. HOWEVER, THE REASON WHY INCREASING ZINC IN THE DIET OF CATTLE IMPROVES GROWTH IS POORLY UNDERSTOOD. THE GOAL OF THIS PROJECT IS TO DETERMINE THE BIOLOGICAL MECHANISMS BY WHICH INCREASING ZINC SUPPLEMENTATION WELL ABOVE DOCUMENTED REQUIREMENTS INCREASES CATTLE GROWTH. OUR WORKING HYPOTHESIS IS THAT RAPID GROWTH INCREASES ZINC REQUIREMENTS OF CATTLE, REGARDLESS OF WHETHER GROWTH IS INCREASED THROUGH USE OF GROWTH PROMOTING TECHNOLOGIES OR DIETARY ENERGY INTAKE. WE WILL CONDUCT A SERIES OF EXPERIMENTS, UTILIZING OUR TRACE MINERAL, CATTLE GROWTH, AND MUSCLE BIOLOGY EXPERTISE TO ADDRESS THE FOLLOWING OBJECTIVES: 1) DETERMINE THE EFFECT OF ALTERING CATTLE GROWTH RATE ON ZINC RETENTION RELATIVE TO MUSCLE GROWTH; 2) DETERMINE IF THE ENHANCEMENT OF CATTLE GROWTH THROUGH ZINC SUPPLEMENTATION IS SPECIFIC TO GROWTH INDUCED WITH TECHNOLOGIES; AND 3) DETERMINE HOW ZINC SUPPLEMENTATION ABOVE CURRENT RECOMMENDATIONS INFLUENCES THE POOL OF ZINC AVAILABLE IN TISSUES CRITICAL TO GROWTH. WE EXPECT TO IDENTIFY SPECIFIC WAYS IN WHICH INCREASING DIETARY ZINC SUPPORTS RAPID GROWTH OF CATTLE, INCLUDING CHANGES IN ZINC ABSORPTION, STORAGE LOCATIONS IN THE BODY, AND CHANGES TO PROTEINS FOUND IN CATTLE MUSCLE. KNOWLEDGE GAINED IN THIS PROJECT COULD IMPROVE SUSTAINABILITY OF THE BEEF INDUSTRY BY SUPPORTING STRATEGIC SUPPLEMENTATION OF ZINC TO INCREASE BEEF PRODUCTION PER ANIMAL, WHICH WILL DECREASE RELIANCE ON NATURAL RESOURCES AND IMPROVE FOOD SECURITY BY POSITIVELY IMPACTING PRODUCER PROFITABILITY.