**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** EARLY PREGNANCY FAILURES CONTINUE TO BE A MAJOR PROBLEM IN THE BEEF AND DAIRY INDUSTRIES RESULTING IN MILLIONS OF DOLLARS LOST IN MEAT AND MILK PRODUCTION. THE MOST SIGNIFICANT WINDOW OF PREGNANCY LOSS OCCURS AROUND DAY 14 - 18 AFTER MATING WHEN SLOW DEVELOPING EMBRYOS FAIL TO PREVENT ONSET OF THE NEXT ESTROUS CYCLE. IMMATURE EMBRYOS ARE UNABLE TO ROBUSTLY COMMUNICATE THEIR PRESENCE, AND THUS PROSTAGLANDIN F2A ESCAPES THE PREGNANT UTERUS AND DESTROYS THE CORPUS LUTEUM (LUTEOLYSIS) AND ITS ESSENTIAL PROGESTERONE SUPPORT TO THE NASCENT PREGNANCY. DATA SHOW THAT SUPPLEMENTING DIETARY OMEGA-3 FATTY ACIDS FROM FISH OIL EXTENDS THE PREGNANCY RECOGNITION WINDOW BY DE-SENSITIZING THE CORPUS LUTEUM TO UTERINE PROSTAGLANDIN F2A, BUT THE UNDERLYING MECHANISMS ARE STILL LARGELY UNKNOWN. A MATURE CORPUS LUTEUM EXPOSED TO PROSTAGLANDIN F2A EXPERIENCES A RAPID (WITHIN 6 HOURS) REDUCTION IN BLOOD FLOW AND DIMINISHED PROGESTERONE PRODUCTION DUE TO DOWNREGULATION OF CRITICAL PROGESTERONE SYNTHESIS GENES. IT IS HYPOTHESIZED THAT DIETARY OMEGA-3 FATTY ACIDS FROM FISH OIL WILL PREVENT PROSTAGLANDIN F2A-INDUCED REDUCTIONS IN LUTEAL BLOOD FLOW AND PROGESTERONE PRODUCTION. THE OBJECTIVES OF THE CURRENT STUDY WILL BE TO DELIVER A NATURAL DOSE OF PROSTAGLANDIN F2A TO CATTLE SYNCHRONIZED TO DAY 14-18 OF THE ESTROUS CYCLE AND DETERMINE WHETHER DIETARY OMEGA-3 FATTY ACIDS PRESERVE LUTEAL: 1) BLOOD FLOW, 2) PROGESTERONE PRODUCTION, AND 3) ABUNDANCE OF KEY PROGESTERONE SYNTHESIS PROTEINS. IT IS ANTICIPATED THAT DIETARY OMEGA-3 FATTY ACIDS FROM FISH OIL WILL REDUCE SENSITIVITY OF THE CORPUS LUTEUM TO A NATURAL PROSTAGLANDIN F2A CHALLENGE, PRESERVING LUTEAL BLOOD FLOW AND SUSTAINING PROGESTERONE SECRETION. OUTCOMES FROM THESE STUDIES WOULD SUGGEST THAT THE REPRODUCTIVE EFFICIENCY OF CATTLE OPERATIONS COULD BE IMPROVED THROUGH DEVELOPMENT OF NOVEL, COST-EFFECTIVE OMEGA-3 FATTY ACID SUPPLEMENTATION STRATEGIES THAT REDUCE LUTEAL PROSTAGLANDIN F2A SENSITIVITY AND MAINTAIN PROGESTERONE SUPPORT FOR THE EMBRYO DURING THE CRITICAL WINDOW THAT A PREGNANCY IS TRYING TO ESTABLISH.