** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** COW-CALF SYSTEMS ARE THE FOUNDATION FOR THE US BEEF INDUSTRY, REPRESENTING 86% OF BEEF OPERATIONS AND 84% OF THE BEEF CATTLE POPULATION IN THE COUNTRY. REPRODUCTIVE FAILURE IS A KEY FACTOR LIMITING COW-CALF PRODUCTIVITY, AND PREGNANCY LOSS HAS BEEN RECOGNIZED AS ONE OF THE MAIN REPRODUCTIVE CHALLENGES IN CATTLE. THE MAJORITY OF PREGNANCY LOSSES OCCUR DURING THE FIRST 28 DAYS OF GESTATION, AND ARE CLASSIFIED AS EARLY EMBRYONIC LOSS. HENCE, MANAGEMENT TO MINIMIZE EARLY EMBRYONIC LOSS IS CRITICAL TO OPTIMIZE EFFICIENCY OF THE US COW-CALF INDUSTRY.OUR GROUP PROVIDED EVIDENCE THAT SUPPLEMENTING BEEF COWS WITH A LIPID SOURCE RICH IN OMEGA-6 FATTY ACIDS DURING THE EARLY EMBRYONIC PERIOD INCREASED PREGNANCY SUCCESS, BY PROMOTING CONCEPTUS DEVELOPMENT AND ESTABLISHMENT/MAINTENANCE OF THE PREGNANCY. THESE RESULTS DIVERGED FROM THE TRADITIONAL CONCEPT THAT OMEGA-6 FATTY ACIDS ARE DETRIMENTAL TO EARLY PREGNANCY BY FAVORING LUTEOLYTIC PATHWAYS. THE MECHANISMS BY WHICH OMEGA-6 FATTY ACIDS IMPROVED PREGNANCY SUCCESS WARRANT FULL CLARIFICATION, WHICH WILL PROVIDE BIOLOGICAL SUPPORT TO NUTRITIONAL INTERVENTIONS THAT MINIMIZE EARLY EMBRYONIC LOSS. THE AIMS PLANNED HEREIN WILL ADDRESS THIS LACK OF KNOWLEDGE BY: #1) COMPARING DIFFERENT LEVELS OF SUPPLEMENTAL OMEGA-6 FATTY ACIDS DURING THE EARLY EMBRYONIC PERIOD USING A COMPREHENSIVE ARRAY OF PHYSIOLOGICAL AND TRANSCRIPTOME ANALYSES; #2) CONTRASTING MOLECULAR AND PHYSIOLOGICAL EFFECTS OF SUPPLEMENTAL OMEGA-6 AND OMEGA-3 FATTY ACIDS ON PREGNANCY ESTABLISHMENT/MAINTENANCE, INCLUDING REPRODUCTIVE AND PRODUCTIVE RESPONSES RELEVANT TO COW-CALF SYSTEMS. COLLECTIVELY, THIS PROPOSAL WILL SUPPORT MANAGEMENT STRATEGIES THAT MITIGATE EARLY EMBRYONIC LOSS; A MAJOR CAUSE OF REPRODUCTIVE AND ECONOMIC LOSSES TO THE US BEEF INDUSTRY.