** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** HEAT STRESS IMPAIRS ANIMAL PERFORMANCE AND HEALTH, LEADING TO ANNUAL LOSSES OF $1.2 BILLION FOR DAIRY, BEEF, AND SWINE INDUSTRIES IN THE U.S. CURRENT HEAT STRESS KNOWLEDGE WAS OBTAINED FROM STUDIES USING FEEDLOT BEEF AND DAIRY BOS TAURUS CATTLE, WHICH HAS LIMITED IMPLICATIONS TO AN UNDERSTUDIED BUT CRUCIAL ANIMAL POPULATION FOR THE U.S. BEEF INDUSTRY (BOS INDICUS-INFLUENCED CATTLE IN GRAZING SYSTEMS) DUE TO DIFFERENCES IN MANAGEMENT AND HOW THIS BREED RESPONDS TO HEAT STRESS. THE RATIONALE OF OUR PROPOSAL IS THAT THE USE OF HEAT ABATEMENT (ACCESS TO SHADE) DURING CRITICAL PERIODS OF PRODUCTION (GESTATION AND EARLY LIFE) IS EXPECTED TO IMPROVE THE PERFORMANCE OF GRAZING BOS INDICUS-INFLUENCED BEEF COWS AND MODULATE THE FUTURE GROWTH, IMMUNE FUNCTION, AND REPRODUCTION OF THEIR OFFSPRING. OUR PRIMARY HYPOTHESIS IS THAT HEAT ABATEMENT OF PREGNANT COWS FOLLOWED BY HEAT ABATEMENT OF THEIR OFFSPRING AFTER BIRTH WILL HAVE THE GREATEST ADDITIVE IMPACTS ON OFFSPRING GROWTH, IMMUNOCOMPETENCE ANDREPRODUCTION. OUR OBJECTIVES ARE TO: (1) IDENTIFY METABOLITES THAT CAN BE USED TO PREDICT COW AND CALF HEAT STRESS RESPONSES; AND (2) EVALUATE THE INDIVIDUAL AND COMBINED IMPACTS OF GESTATIONAL AND EARLY LIFE HEAT STRESS ABATEMENT ON PERFORMANCE AND METABOLIC RESPONSES OF GRAZING BEEF CATTLE. WE EXPECT THAT: (1) MULTIPLE METABOLITES, PHYSIOLOGICAL AND PERFORMANCE RESPONSES WILL DIFFER BETWEEN PREGNANT COWS PROVIDED OR NOT ACCESS TO HEAT ABATEMENT, AND SUCH DIFFERENCES WILL ILLUSTRATE THE PRECISE IMPACTS OF HEAT STRESS IN GRAZING BOS INDICUS-INFLUENCED BEEF COWS; AND (2) HEAT STRESS EXPOSURE DURING GESTATION WILL ALSO ALTER MULTIPLE MOLECULAR, METABOLIC, AND PHYSIOLOGICAL MECHANISMS OF THE OFFSPRING, LEADING TO IMPAIRED ABILITY OF THE OFFSPRING TO COPE WITH HEAT STRESS DURING EARLY LIFE. THIS PROPOSAL WILL LEAD TO A BETTER UNDERSTANDING OF THE CAUSES AND PROVIDE THE FOUNDATION TO DEVELOP MANAGEMENT PRACTICES TAILORED TO IMPROVE THE PRODUCTIVITY OF BOS INDICUS-INFLUENCED BEEF CATTLE IN TROPICAL/SUBTROPICAL ENVIRONMENTS AND ADDRESS A FUNDAMENTAL STEP TO MEET THE RISING GLOBAL DEMAND FOR BEEF.