THE PROPOSED PROJECT SEEKS TO EVALUATE IF A NATIONAL GENOMIC EVALUATION FOR HEAT STRESS TOLERANCE IN THE UNITED STATES HOLSTEIN POPULATION. IS FEASIBLE.THE CURRENT NATIONAL EVALUATION DOES NOT INCLUDE INFORMATION ABOUT HEAT STRESS NOR CONSIDERS SEASONAL FLUCTUATIONS AS CONSEQUENCES OF ANIMALS' INDIVIDUAL GENETIC FACTORS. THEREFORE, WE AIM TO IDENTIFY HEAT TOLERANT BULLS WITHIN THE POPULATION.THE EFFECTS OF HEAT STRESS IN DAIRY CATTLE ACROSS THE US ARE WELL DESCRIBED IN THE LITERATURE. ADDITIONALLY, BASED ON PREVIOUS PUBLICATIONS GENETICS PLAY AN IMPORTANT ROLE IN TOLERANCE TO HIGH TEMPERATURES. TO FULFILL OUR GOALS, WE WILL MODIFY THE MODELS USED IN THE NATIONAL EVALUATION TO INCLUDE WEATHER INFORMATION IN THE EVALUATION PROCESS. THIS PROJECT COUNTS WITH A COLLABORATIVE TEAM OF ANIMAL BREEDERS WITH COMPLEMENTARY BACKGROUNDS. WE ALSO COUNT ON THE COLLABORATION OF STAKEHOLDERS, WHICH WILL PROVIDE ACCESS TO THE NATIONAL US HOLSTEIN DATABASE, INCLUDING PEDIGREE, PHENOTYPES, AND GENOTYPES.WE WILL SHOW HOW THE GENETICS FOR MILK,PROTEIN AND FAT YIELD, AND SOMATIC CELL COUNT ARE ASSOCIATED WITHTHE TEMPERATURE AND RELATIVE HUMIDITY OF THE AIR. WE WILL PROVIDE ANIMAL EVALUATION FOR SPECIFIC ENVIRONMENTS, AND WE WILL WORK WITH THE STAKEHOLDERS TO COMMUNICATE OUR RESULTS INMEANINGFUL WAY FOR DAIRY PRODUCERS. WE WILL PERFORM A GENOME-WIDE ASSOCIATION STUDY TO LEARN ABOUT THE GENES UNDERLYING THE HEAT STRESS TOLERANCE IN THE US HOLSTEIN POPULATION. THIS SEED GRANT WILL HELP START A COLLABORATIVE TEAM TO STUDY THE INTERACTION OF GENETICS AND ENVIRONMENT IN THE US DAIRY POPULATION. WE INTEND TO GENERATE INITIAL DATA FOR A FUTURE NIFA STANDARD APPLICATION ADDRESSING THE HIGH PRIORITY AREA OF ANIMAL HEALTH AND PRODUCTION AND ANIMAL PRODUCTS BY DEVELOPING A NATIONAL BREEDING STRATEGY TO ADDRESS ABIOTIC STRESS CAUSED BY CLIMATE VARIABILITY.