**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** METRITIS IS A POST-CALVING UTERINE INFECTION THAT AFFECTS ABOUT 20% OF DAIRY CATTLE IN THE UNITED STATES. THE MOST COMMON TREATMENT METHOD FOR METRITIS IS ANTIBIOTICS, AND WHILE THEY ARE EFFECTIVE, THE GROWTH OF ANTIBIOTIC RESISTANCE MEANS THIS THERAPEUTIC OPTION MIGHT NOT BE AVAILABLE IN THE FUTURE. METRITIS IS SCIENTIFICALLY PROVEN TO BE A PAINFUL DISEASE, AND THEREFORE, NOT PROVIDING ADEQUATE TREATMENT IS SEEN AS AN ANIMAL WELFARE ISSUE. SEVERAL ALTERNATIVE TREATMENTS HAVE BEEN TESTED BY RESEARCHERS; HOWEVER, THIS STUDY GOES ONE STEP FURTHER AND SUGGESTS A PREVENTATIVE MEASURE FOR THE DEVELOPMENT OF METRITIS- A SINGLE DOSE OF ASPIRIN. ASPIRIN IS CLASSIFIED AS A NON-STEROIDAL ANTI-INFLAMMATORY DRUG MEANING IT ALTERS THE WAY THE BODY RESPONDS TO INJURY OR INFECTION. THE INFLAMMATORY RESPONSE OF THE COW TRANSITIONING THROUGH CALVING AND LACTATION STARTS AROUND 14 DAYS PRE-CALVING. THE STUDY WILL ADMINISTER A SINGLE DOSE OF ASPIRIN (OR A PLACEBO) AT THAT TIME AND THEN MONITOR THE LEVELS OF INFLAMMATION IN THE REPRODUCTIVE TRACT AFTER CALVING ALONG WITH DOCUMENTING WHETHER COWS DEVELOP METRITIS. THE OTHER AIM OF THIS STUDY IS TO MONITOR CHANGES IN THE COWS' REPRODUCTIVE MICROBIOME, WHICH ARE THE BACTERIA THAT LIVE WITHIN A GIVEN ORGAN SYSTEM AND SUPPORT NORMAL PHYSIOLOGICAL FUNCTIONS. THIS STUDY TESTS THE RESEARCH HYPOTHESIS THAT COWS ADMINISTERED ASPIRIN WILL HAVE LESS INFLAMMATION IN THE POST-CALVING PERIOD AND LESS CHANGES IN THEIR REPRODUCTIVE MICROBIOME, THUS LEADING TO LESS INCIDENCE OF METRITIS. THE IMPACT OF THIS PROJECT WILL NOT ONLY REDUCE ANIMAL DISEASE, BUT ALSO DECREASE ANTIBIOTIC USE IN DAIRY CATTLE, THUS PRESERVING ANTIBIOTIC USAGE FOR CRITICAL AREAS OF NEED SUCH AS HUMAN HEALTH. THE RESULTS OF THE STUDY WILL BE DISSEMINATED TO MULTIPLE STAKEHOLDER GROUPS INCLUDING FOOD ANIMAL VETERINARIANS, EXTENSION AGENTS, AND DAIRY PRODUCERS IN BOTH SCIENTIFIC PUBLICATIONS AS WELL AS EXTENSION ARTICLES ACCESSIBLE TO THE GENERAL PUBLIC.