WITH MORE SEVERE AND FREQUENT HIGH ENVIRONMENTAL TEMPERATURES, HEAT STRESS (HS) IS ONE OF THE MOST DETRIMENTAL ISSUES THE PORK INDUSTRY FACES. HEAT STRESS IS COMPLEX, NEGATIVELY IMPACTING ANIMAL GROWTH, REPRODUCTION, CARCASS QUALITY, AND OVERALL ANIMAL WELFARE. TOGETHER, THESE LOSSES APPROACH $1 BILLION ANNUALLY IN THE UNITED STATES, EVEN WITH MITIGATION STRATEGIES. EVEN WITH INNOVATIONS IN HEAT ABATEMENT STRATEGIES SUCH AS FACILITY COOLING SYSTEMS, REDUCED PRODUCTION STILL PERSISTS AND COOLING FAILS TO ADDRESS THE UNDERLYING CELLULAR PATHOLOGIES ASSOCIATED WITH HS. GAPS IN KNOWLEDGE, INCLUDING THE IMPACT OF BIOLOGICAL SEX, LIMITS THE TREATMENT AND PREVENTION OF HS-MEDIATED PATHOLOGIES. CONSEQUENTLY, THERE IS A CRITICAL NEED TO ESTABLISH TO WHAT DEGREE HS DIFFERENTIALLY IMPACTS MUSCLE IN GILTS AND BARROWS. EMERGING EVIDENCE FROM OUR LAB GROUP AND OTHERS SUGGESTS A SEX EFFECT IN THE HS RESPONSE. MY CENTRAL HYPOTHESIS IS THAT SKELETAL MUSCLE COLLECTED FROM BARROWS WILL BE MORE RESILIENTTO HS-MEDIATED DYSFUNCTION THAN MUSCLE FROM HEAT-STRESSED GILTS. IN AIMS 1 AND 2 I WILL PERFORM PROTEOMICS AND PHOSPHO-PROTEOMICS IN SKELETAL MUSCLE AND MITOCHONDRIA FRACTIONS ISOLATED FROM SKELETAL MUSCLE COLLECTED FROM HEAT-STRESSED AND TN BARROWS AND GILTS. IN AIM 3 I WILL PERFORM TRANSCRIPTOMICS ON SKELETAL MUSCLE TO GAIN MORE INSIGHT INTO HS-MEDIATED CHANGES IN BARROWS AND GILTS. THE DATA COLLECTED FROM THESE AIMS WILL BE USED TO PUBLISH SCIENTIFIC RESEARCH PUBLICATIONS AND PRESENTED AT SCIENTIFIC CONFERENCES. MORE IMPORTANTLY, THE IDENTIFIED DIFFERENCES MAY LEAD TO IDENTIFICATION OF NOVEL TARGETS FOR THERAPEUTIC STRATEGIES TO MITIGATE THE NEGATIVE IMPACTS OF HS ON ANIMAL WELFARE AND PRODUCTION. ADDITIONALLY, THESE CAN LEAD TO ALTERATIONS IN MANAGEMENT STRATEGIES AND ENCOURAGE SINGLE SEX PRODUCTION SYSTEMS AND EVEN IMPACT THE DISTRIBUTION OF SEXES WITHIN PRODUCTION SYSTEMS.