**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** SUSTAINABLE BEEF PRODUCTION REQUIRES EFFICIENT REPRODUCTIVE PERFORMANCE IN THE COW HERD. SUB-OPTIMAL REPRODUCTIVE PERFORMANCE IS CAUSED BY THE INABILITY OF FEMALES TO SUPPORT THE GROWTH OF AN EMBRYO AND MAINTAIN A PREGNANCY. A LARGE PROPORTION OF FAILURE OCCURS DURING EARLY GESTATION, BECAUSE OF A NON-RECEPTIVE UTERUS. THERE IS A CRITICAL NEED TO DEFINE THE NATURE AND THE ABUNDANCE OF MOLECULES PRESENT IN THE UTERINE LUMEN WHEN A PREGNANCY SUCCEEDS. WE PROPOSE EXPERIMENTS TO COMPARE THE ENDOMETRIAL TRANSCRIPTOME AND METABOLOME OF ANIMALS THAT SUCCEEDED OR FAILED TO BECOME PREGNANT, IN SEQUENTIAL PREGNANCY OPPORTUNITIES (EXPERIMENT 1). WE ALSO PROPOSE TO TEST A STRATEGY TO MORE ADEQUATELY PROGRAM UTERINE FUNCTION TO INCREASE RECEPTIVITY TO THE EMBRYO AND BETTER SUPPORT GESTATION (EXPERIMENT 2). THE BASIC AND APPLIED ASPECTS OF THE CURRENT PROPOSAL HAVE MANY PREDICTED POSITIVE OUTCOMES. FOR EXAMPLE, WE WILL FOR THE FIRST TIME CHARACTERIZE THE MOLECULAR FACTORS ASSOCIATED WITH EMBRYO RECEPTIVITY. SUCH EVIDENCE HAS THE POTENTIAL TO LEAD TO THE GENERATION OF NON-GENOMIC MARKERS THAT CAN BE USED FOR THE SELECTION OF EMBRYO RECIPIENTS. MARKERS MAY BE USED IN FUTURE STUDIES, FOR EXAMPLE, TO STUDY THE INFLUENCE OF BREEDS AND CROSSES, SEASON, STRESS, LACTATION, SYNCHRONIZATION STRATEGIES, NUTRITIONAL STRATEGIES, ENERGY STATUS ETC. ON THE UTERINE ENVIRONMENT AND ITS ABILITY TO SUPPORT PREGNANCY. MOLECULAR DIFFERENCES BETWEEN PREGNANT AND NON-PREGNANT ANIMALS WILL BE USED BOTH AS MARKERS FOR PROGNOSTICS OF PREGNANCY OUTCOME AND AS TARGETS TO RESEARCH ON UTERINE FUNCTION TO SUPPORT PREGNANCY. NEW INFORMATION GENERATED FROM OUR PRE-ESTRUS PROGRAMMING OF UTERINE RECEPTIVITY TO ESTRUS EXPERIMENT WILL SERVE AS THE BASIS FOR THE OPTIMIZATION OF STRATEGIES FOR ESTRUS SYNCHRONIZATION AIMING ARTIFICIAL INSEMINATION OR EMBRYO TRANSFER. WE ANTICIPATE HAVING GENERATED NEW KNOWLEDGE AND TOOLS TO BE USED FOR BASIC AND APPLIED RESEARCH, AS WELL AS USED BY BEEF PRODUCERS TO INCREASE PREGNANCYSUCCESS IN COW-CALF OPERATIONS. BECAUSE REPRODUCTIVE EFFICIENCY IS A CORE ASPECT OF SUSTAINABLE BEEF COW-CALF OPERATIONS, PRODUCTION OF STRATEGIES AND TOOLS THROUGH SUCCESSFUL COMPLETION OF OUR PROPOSED RESEARCH IS EXPECTED TO CONTRIBUTE DIRECTLY TO LONG-RANGE IMPROVEMENT AND SUSTAINABILITY OF US AGRICULTURE AND FOOD SYSTEMS.