HEAT STRESS NEGATIVELY IMPACTS SWINE WELL-BEING RESULTING IN GREATERMORTALITY, AND REDUCED WELFARE CONTINUES TO OCCUR DESPITE ADVANCES IN LIVESTOCK COOLING SYSTEM TECHNOLOGIES AND MANAGEMENT STRATEGIES. WITH AN INCREASE IN THE MAGNITUDE AND FREQUENCY OF EXTREME HOT WEATHER EVENTS OCCURRING GLOBALLY, THE NEED TO REFINE AND RE-DEVELOP HEAT STRESS MITIGATION AND MANAGEMENT STRATEGIES IS OF UTMOST IMPORTANCE. THE FIRST STEP IN DEVELOPING MITIGATION STRATEGIES IS TO IDENTIFY WHEN SOWS ARE EXPERIENCING HEAT STRESS. DESPITE THE NEED FOR THIS BASIC INFORMATION, CURRENT HEAT STRESS GUIDELINES FOR SWINE ARE BASED ON DATA THAT IS OVER 30 YEARS OLD. THEREFORE, IT IS LIKELY THAT THESE GUIDELINES ARE INACCURATE CONSIDERING THAT IMPROVEMENTS IN SOW PRODUCTIVITY HAVE INCREASED METABOLIC RATE BY 16% IN MODERN SOWS. FURTHERMORE, THE AVAILABILITY OF A USER-FRIENDLY DECISION SUPPORT TOOL FOR SWINE PRODUCERS TO PREDICT WHEN SOWS ARE EXPERIENCING HEAT STRESS IS NON-EXISTENT. THE OVERALL OBJECTIVE OF THIS PROPOSAL IS TO RE-EVALUATE TEMPERATURE THRESHOLDS THAT RESULT IN HEAT STRESS IN MODERN SOWS AND DEVELOP A DECISION SUPPORT TOOL TO ASSIST SWINE PRODUCERS WITH MANAGEMENT DECISIONS DURING TIMES OF HEAT STRESS. SPECIFIC OBJECTIVES ARE TO: 1) RE-EVALUATE THERMAL PREFERENCES BASED ON SOW PERCEPTION, 2) DETERMINE PHYSIOLOGICAL RESPONSE TO INCREASING AMBIENT TEMPERATURES, AND 3) DEVELOP A DECISION SUPPORT TOOL TO IMPROVE SOW WELFARE DURING HEAT STRESS. SUCCESSFUL COMPLETION OF THIS PROPOSAL WILL UPDATE OR VALIDATE THE CURRENT RECOMMENDATIONS FOR HEAT STRESS IN MODERN SOWS AND PROVIDE SWINE PRODUCERS WITH A DECISION SUPPORT TOOL TO DETERMINE WHEN TO INTERVENE DURING TIMES OF HEAT STRESS.