OVER THE PAST TWO DECADES, A REPRODUCTION REVOLUTION HAS OCCURRED IN THE DAIRY INDUSTRY THAT HAS LED TO DRAMATIC INCREASES IN REPRODUCTIVE PERFORMANCE IN HIGH-PRODUCING COWS. A CONSEQUENCE OF INCREASED REPRODUCTIVE PERFORMANCE WAS A CONCURRENT INCREASE IN REPLACEMENT HEIFER INVENTORIES WHICH DROVE DOWN REPLACEMENT HEIFER VALUES. TO COMPENSATE FOR THESE CHANGING ECONOMIC CONDITIONS, FARMERS HAVE TURNED TO USE OF SEXED SEMEN IN BOTH NULLIPAROUS HEIFERS AND PRIMIPAROUS COWS TO RIGHT-SIZE REPLACEMENT HEIFER INVENTORIES AND MAXIMIZE PROFIT.THIS PROJECT WILL USE BOTH BIOLOGICAL AND REPRODUCTIVE MANAGEMENT RESEARCH DATA WITH NOVEL ECONOMIC MODELING TOOLS TO FOSTER POSITIVE CHANGE IN THE DAIRY INDUSTRY THROUGH PROACTIVE EXTENSION PROGRAMMING TO: 1) ADDRESS CRITICAL KNOWLEDGE GAPS IN THE BIOLOGY AND PRACTICAL IMPLEMENTATION OF USE OF SEXED SEMEN ON DAIRY FARMS THROUGH ON FARM FIELD TRIALS AND IN VITRO EXPERIMENTS; 2) DEVELOP ECONOMIC DECISION-MAKING TOOLS FOR OPTIMIZING HEIFER INVENTORY MANAGEMENT, HERD TURNOVER RATE, AND SEMEN TYPE USE IN DAIRY HERDS; AND 3) DELIVER RESEARCH-BASED DATA SUPPORTED BY ECONOMIC DECISION MAKING TOOLS TO THE U.S. DAIRY INDUSTRY THROUGH A NATIONWIDE MULTI-PLATFORM EXTENSION PROGRAM. BIOLOGICAL DATA THAT ADDRESS CRITICAL KNOWLEDGE GAPS REGARDING SEXED SEMEN SUPPORTED BY ECONOMIC MODELING TOOLS THAT HELP DAIRY FARMERS OPTIMIZE DAIRY HERD STRUCTURE AND TURNOVER RATE ARE CRITICALLY NEEDED AT THIS JUNCTURE IN THE DAIRY INDUSTRY. THUS, THE LONG-TERM GOAL OF THIS PROPOSAL IS TO OPTIMIZE STRATEGIES FOR USE OF SEXED SEMEN IN DAIRY HERDS.