** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE DAIRY INDUSTRY PLAYS A MAJOR ROLE IN THE U.S. NATIONAL AGRICULTURAL ECONOMY. DAIRY ANIMALS HAVE UNDERGONE A RAPID IMPROVEMENT IN MILK PRODUCTIVITY - BUT NOT WITHOUT A COST. FOR MANY YEARS, THIS INCREASE IN THE GENETIC MERIT OF DAIRY COWS FOR IMPROVED MILK YIELDS, HAS BEEN ASSOCIATED WITH FERTILITY DECLINE. EARLY EMBRYONIC LOSS IS A MAJOR CAUSE OF THIS FERTILITY DECLINE, WHICH IS ACCOMPANIED WITH CONSIDERABLE NEGATIVE ECONOMIC IMPLICATIONS. OUR LONG-TERM GOAL IS TO IMPROVE THE FERTILITY OF MODERN DAIRY COWS BY UNCOVERING THE MOLECULAR MECHANISMS REGULATING PREIMPLANTATION EMBRYO DEVELOPMENT, PRIOR TO MANIPULATING THESE MECHANISMS TO IMPROVE EMBRYO QUALITY, THEREBY IMPROVING REPRODUCTIVE EFFICIENCY. WE PREVIOUSLY SHOWED THAT REGULATING CATHEPSIN B (A PROTEASE ENZYME) IS A PROMISING APPROACH TO IMPROVING EMBRYO QUALITY. OUR SPECIFIC AIMS ARE TO: (1) DETERMINE THE UNDERLYING MOLECULAR MECHANISMS BY WHICH CATHEPSIN B PERTURBS EMBRYO QUALITY, AND (2) IDENTIFY OTHER PROTEASES THAT SIMILARLY COMPROMISE BOVINE EMBRYO QUALITY. SUCCESSFUL COMPLETION OF THE PROPOSED AIMS IS EXPECTED TO FILL A SUBSTANTIAL GAP IN OUR KNOWLEDGE OF HOW EARLY EMBRYO DEVELOPMENT IS CONTROLLED, AND TO PROVIDE NEW APPROACHES TO IMPROVING EMBRYO QUALITY.DISSECTING THE MOLECULAR MECHANISMS UNDERLYING HOW CATHEPSINS COMPROMISE EARLY EMBRYO DEVELOPMENT AND QUALITY IS EXTREMELY IMPORTANT TO DEVELOPING EFFECTIVE APPROACHES TO IMPROVING THE EFFICIENCY OF BOVINE IN VITRO EMBRYO PRODUCTION, WHILST SIMULTANEOUSLY REVEALING SOLUTIONS FOR ENHANCING REPRODUCTIVE EFFICIENCY IN HIGH-YIELDING DAIRY COWS; SUBSEQUENTLY IMPROVING THE ANIMAL PRODUCTION ECONOMY OF THE USA.