**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** SELECTION OF A SINGLE DOMINANT FOLLICLE IS A KEY REPRODUCTIVE PROCESS. IN SOME SITUATIONS, TWO OR MORE FOLLICLES MAY BE SELECTED AND THIS IS THE PRIMARY REASON FOR THE HIGH TWINNING RATE IN LACTATING DAIRY COWS. THUS, WE ARE TRYING TO UNDERSTAND AND POTENTIALLY CONTROL DOUBLE OVULATION AND TWINS. IN ADDITION, ALL THE IMPORTANT REPRODUCTIVE BIOTECHNOLOGIES, SUCH AS EMBRYO PRODUCTION AND TRANSFER, REQUIRE COLLECTION OF OOCYTES FROM NORMALLY DEVELOPED FOLLICLES. WE DO NOT UNDERSTAND THIS PROCESS SUFFICIENTLY. THIS PROJECT WILL HELP US TO UNDERSTAND WHAT CONTROLS THE PROCESS OF FOLLICLE SELECTION AND NORMAL FOLLICLE DEVELOPMENT.WE HYPOTHESIZE THAT PULSES OF TWO HORMONES, LH AND FSH, ARE KEY FOR CONTROLLING THE PROCESS FOR SELECTING A SINGLE DOMINANT FOLLICLE. WE WILL TEST THIS IDEA UNDER NORMAL CONDITIONS IN HEIFERS AND IN LACTATING DAIRY COWS. THIS WILL DEFINE THE NORMAL HORMONAL CHANGES ASSOCIATED WITH FOLLICLE SELECTION.WE WILL ALSO DETERMINE HOW HORMONES FROM THE OVARY, ESTRADIOL AND PROGESTERONE, REGULATE LH AND FSH PULSES. WE DETERMINE HOW CHANGING LH AND FSH PULSES WILL CHANGE PATTERNS OF FOLLICLE GROWTH. WE WILL ALSO TEST HOW THE FOLLICLE CHANGES THE GENES THAT ARE EXPRESSED IN THE CELLS OF THE FOLLICLE DURING FOLLICLE SELECTION. THESE EXPERIMENTS WILL DIRECTLY TEST OUR IDEAS ABOUT FOLLICLE SELECTION AND ALLOW US TO MODIFY AND IMPROVE OUR MODEL. OUR FINAL OBJECTIVE IS TO DETERMINE WHAT CAUSES MANY HIGH PRODUCING DAIRY COWS TO SELECT TWO OR MORE FOLLICLES RATHER THAN A SINGLE DOMINANT FOLLICLE. THIS LEADS TO THE HIGH NUMBERS OF TWINS THAT ARE BORN TO LACTATING DAIRY COWS. BIRTH OF TWINS LEADS TO MAJOR METABOLIC AND DISEASE PROBLEMS IN THE COWS.THUS, THIS RESEARCH IS FOCUSED ON OBTAINING A DEEP UNDERSTANDING OF THE FOLLICLE SELECTION PROCESS. THIS DEEPER UNDERSTANDING WILL ALLOW US TO RATIONALLY DEVELOP PROGRAMS THAT WILL IMPROVE REPRODUCTION IN CATTLE INCLUDING REDUCING NUMBER OF TWINS IN DAIRY COWS.