MORE THAN HALF OF THE CATTLE IN THE WORLD, INCLUDING 40-45% OF CATTLE IN THE US, ARE MAINTAINED IN HOT ENVIRONMENTS WHERE HEAT STRESS CONDITIONS IMPEDE GROWTH, PRODUCTION AND REPRODUCTION. GREATER DEMAND FOR ANIMAL PROTEINS TOGETHER WITH THE NEGATIVE EFFECTS OF RAPID CLIMATE CHANGE, IF NOT DEALT WITH, ARE LIKELY TO CREATE LARGE PRODUCTIVITY GAPS IN THE NEAR FUTURE. TWO APPROACHES CAN BE USED TO MITIGATE THE EFFECTS OF HEAT STRESS ON BEEF CATTLE PRODUCTION: MANAGEMENT INTERVENTIONS TO CONTROL THE CLIMATE AND SELECTION FOR INCREASED THERMOTOLERANCE. BEEF CATTLE, PARTICULARLY THOSE IN THE COW-CALF SEGMENT, ARE TYPICALLY REARED IN EXTENSIVE SYSTEMS WITH LIMITED OPPORTUNITIES FOR CONTROLLING ENVIRONMENTAL STRESS. GENETIC IMPROVEMENT OF THERMOTOLERANCE IS ONE OF THE FEW FEASIBLE STRATEGIES FOR ENSURING ADEQUATE AND SUSTAINABLE PRODUCTION OF BEEF PROTEIN IN AN INCREASINGLY HOTTER WORLD.OUR LONG-TERM GOAL IS TO DEVELOP THE KNOWLEDGE AND TOOLS THE CATTLE INDUSTRY WILL USE TO INCREASE TOLERANCETO HEAT STRESS, WHILE SIMULTANEOUSLY ALLOWING FOR INCREASED EFFICIENCY OF PRODUCTION, REPRODUCTION, AND MEAT QUALITY. THE GOAL OF THIS PROPOSAL IS TO IDENTIFY AND INTEGRATE FUNCTIONAL GENOMICS INFORMATION ABOUT HEAT EXCHANGE ABILITY INTO GENOMIC EVALUATION FOR INCREASED PRODUCTIVITY.WE WILL GENERATE WHOLE-GENOME SEQUENCE AND GENE EXPRESSION DATA TO DEFINE THE TRANSCRIPTOME AND IDENTIFY DNA VARIATION FOR INCREASED HEAT EXCHANGE ABILITY (OBJECTIVE 1). WE WILL INTEGRATE RNA-SEQ, CHIP-SEQ AND ATAC-SEQ TO DETERMINE FUNCTIONAL ROLES OF GENOME REGULATORY REGIONS (OBJECTIVE 2). FUNCTIONAL GENOMICS DATA WILL BE INTEGRATED INTO GENOMIC EVALUATION TO INCREASE ACCURACY AND INCREASE THERMOTOLERANCE WITHOUT NEGATIVE IMPACT ON PRODUCTIVITY (OBJECTIVE 3).GENOMIC SELECTION TO IMPROVE THERMAL ADAPTATION WILL PROVIDE A PATHWAY TOWARD A SUSTAINABLE INTENSIFICATION OF PRODUCTION TO ADDRESS THE INCREASED DEMAND FOR ANIMAL PROTEIN AND MEET THE CHALLENGE OF GLOBAL CLIMATE CHANGE.