**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** REPRODUCTIVE FAILURE WEIGHS HEAVILY ON THE MINDS OF CATTLE PRODUCERS. ESTIMATED PERCENTAGE OF FEMALES FAILING TO BECOME PREGNANT AFTER A SINGLE INSEMINATION RANGES FROM 35 TO 40% IN BEEF AND MAY BE AS HIGH AS 50 TO 70+% IN DAIRY CATTLE. FAILURES OF THIS MAGNITUDE ARE NOT SUSTAINABLE AND ARE INCREDIBLY COSTLY TO THE US CATTLE INDUSTRY. WHILE BASIS FOR FAILURE IS MULTI-FACTORIAL, HEIGHTENED LEVELS OF ESTRUS ACTIVITY MATTER WHEN PREGNANCY IS A DESIRED OUTCOME AFTER BREEDING. ACTIVITY IS A MAJOR DRIVER OF ELEVATED BODY TEMPERATURE IN FEMALES EXHIBITING ESTRUS. THE CENTRAL HYPOTHESIS TO BE TESTED IN THIS PROPOSAL IS HIGHER ESTRUS-ASSOCIATED BODY TEMPERATURES (HEAT) IS FUNCTIONALLY IMPORTANT TO MAXIMIZE PREGNANCY OUTCOMES THROUGH DIRECT EFFECTS ON OVULATORY FOLLICLE COMPONENTS, ESPECIALLY THE OOCYTE AND ITS SURROUNDING CUMULUS CELLS. TO TEST HYPOTHESIS, TWO SPECIFIC AIMS WILL BE PURSUED: 1) DETERMINE THE EXTENT TO WHICH AN ACUTE EPISODE OF ELEVATED BODY TEMPERATURE IN ESTRUAL FEMALES DIRECTLY IMPACTS OVULATORY FOLLICLE COMPONENTS, AND 2) IDENTIFY CUMULUS-OOCYTE FACTORS PROMOTING MEIOTIC MATURATION WHEN APPROPRIATELY ACTIVATED BY HEAT. THIS NOVEL RESEARCH UTILIZES ORIGINAL AND COMPLEMENTARY BASIC AND APPLIED STUDIES. IF CONFIRMED, OUTCOMES WOULD PROVIDE INVALUABLE INSIGHT REGARDING INEXPENSIVE APPROACHES TO IMPROVING FERTILITY IN CATTLE. ANSWERS TO THIS INTERESTING QUESTION COULD LEAD TO SIGNIFICANT GAINS IN THE MANAGEMENT OF REPRODUCTION TO IMPROVE PREGNANCY RATES.