MEASURING TOTAL ENERGY USE AND EFFICIENCY, AS WELL AS GREENHOUSE AND ODORANT GAS EMISSIONS, IS NECESARRY TO DEVOLOP NUTRITIONAL AND MANAGMENT APPROACHES TO IMPROVE THE SUSTAINABILITY OF THE BEEF CATTLE INDUSTRY. AN OPEN-CIRCUIT INDIRECT CALORIMETRY SYSTEM WITH CUSTOM-BUILT HEAD-HOOD BOXES WILL BE DEVELOPED FOR MEASURING GAS EXHANGE IN CATTLE. THE SYSTEM WILL ALLOW US TO MEASURE DIETARY ENERGY USE AND EFFICIENCY IN INDIVIDUAL CATTLE FED DIFFERENT DIETS OR UNDER DIFFERENT MANAGEMENT STRATEGIES. ADDITIONALLY, THE SYSTEM WILL ALLOW FOR THE MEASUREMENT OF GREENHOUSE AND ODORANT GAS EMISSIONS FROM INDIVIDUAL CATTLE. THE EQUIPMENT WILL ALLOW TO STUDY SPECIFIC RESEARCH FOCUS AREAS SUCH AS: 1) PHYSIOLOGICAL FACTORS INFLUENCING EFFICIENCY OF NUTRIENT UTILIZATION IN CATTLE, 2) EFFECTS OF NUTRITIONAL MANAGEMENT ON THE EFFICIENCY OF NUTRIENT UTILIZATION IN CATTLE, 3) EFFECTS OF NUTRITION ON NUTRIENT EXCRETION AND GREENHOUSE GAS EMISSIONS FROM CATTLE OPERATIONS, 4) EFFECTS OF ENVIRONMENT ON DIETARY ENERGY REQUIREMENTS, 5) ROLE OF DEVELOPMENTAL PROGRAMMING DURING EARLY FETAL OR NEONATAL GROWTH ON EFFICIENCY OF NUTRIENT UTILIZATION, AND 6) DEVELOPMENT OF IMAGING PROTOCOLS TO PREDICT ANIMAL CHARACTERISTICS AND/OR EFFICIENCY OF DIETARY NUTRIENT AND ENERGY UTILIZATION FOR USE IN PRECISION MANAEMENT PROGRAMS.