HEAT STRESS IS A COSTLY PROBLEM FOR THE US DAIRY INDUSTRY, NEGATIVELY IMPACTING MILK YIELD, FERTILITY, AND CATTLE HEALTH AND WELFARE. CURRENT HEAT ABATEMENT SOLUTIONS USING WATER AND/OR FANS HAVE SIGNIFICANT SHORTFALLS, AND VENTILATION SYSTEMS ARE TYPICALLY DESIGNED FOR BARN-LEVEL AIR EXCHANGE WITHOUT CONSIDERING THE MICROCLIMATE IN THE LYING STALLS WHERE COWS SPEND HALF OF THEIR DAY. PUBLISHED DATA ARE LACKING ON THE MINIMUM AIRSPEED REQUIRED TO PROMOTE SUFFICIENT CATTLE RESTING TIME IN HOT WEATHER, AND NO STUDIES ON AIR FLOW AND HEAT EXCHANGE HAVE BEEN CONDUCTED ON HIGH-PRODUCING COWS IN FREESTALLS. DATA ARE NEEDED TO SUPPORT PRACTICAL SOLUTIONS FOR REDUCING HEAT STRESS TO IMPROVE HEALTH AND WELFARE IN HIGH-PRODUCING COWS. WE HYPOTHESIZE THAT DIRECTING CONSISTENT FAST-MOVING AIR TO THE COWS' LEVEL WILL REDUCE HEAT STRESS, IMPROVE COW COMFORT AND TIME BUDGETS, AND INCREASE MILK YIELD. OUR GOAL IS TO PROVIDE DAIRY PRODUCERS TOOLS TO CHARACTERIZE THE MICROCLIMATES THROUGHOUT THEIRBARNS, ASSESS ANIMAL INDICATORS OF HEAT STRESS, AND IDENTIFY SOLUTIONS FOR THEIR HERDS. WE PROPOSE TO 1) GENERATE EXPERIMENTAL DATA TO SUPPORT RECOMMENDATIONS FOR BEST HEAT ABATEMENT PRACTICES AND 2) DELIVER A MULTI-PLATFORM TECHNOLOGY-TRANSFER PROGRAM EXTENDING ACROSS THE US DAIRY SECTOR. AS A RESULT, WE EXPECT AN IMPROVED UNDERSTANDING OF ALLEVIATING HEAT STRESS BY TARGETING THE COWS' MICROENVIRONMENTS, ALONG WITH RAPID ADOPTION OF OUR EVIDENCE-BASED BEST PRACTICES. OUR PROJECT WILL FILL THE EVIDENCE AND TRAINING GAP TO GIVE DAIRY PRODUCERS, CONSULTANTS, AND VETERINARIANS THE TOOLS NEEDED TO MAKE THE BEST DECISIONS FOR EACH HERD. ULTIMATELY, IMPROVING DAIRY CATTLE WELL-BEING, WILL RESULT IN IMPROVED PUBLIC PERCEPTION OF FOOD ANIMAL PRODUCTION, HELPING TO ENSURE THE LONG-TERM SUSTAINABILITY OF U.S. DAIRY PRODUCTION.