**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** MEAT PRODUCTION IS THE PRIMARY GOAL OF THE TURKEY INDUSTRY. SELECTION FOR GROWTH PRODUCTION HAS NEGATIVELY IMPACTED THE REPRODUCTIVE PERFORMANCE OF BREEDING HENS. THE NUMBER OF EGGS LAID PER HEN GREATLY IMPACTS THE NUMBER OF YOUNG TURKEYS (POULTS) THAT CAN BE REARED FOR MEAT PRODUCTION. LOW EGG PRODUCING HENS COST THE INDUSTRY ROUGHLY $50 MILLION A YEAR IN LOST POULT PRODUCTION (250 MILLION TURKEYS/YEAR AT $1-$2 PER FERTILE TURKEY EGG). INCREASING THE NUMBER OF EGGS LOW EGG PRODUCING HENS LAY IN A GIVEN CYCLE WOULD BE BENEFICIAL TO THE TURKEY INDUSTRY, THOUGH THE BIOLOGICAL MECHANISMS LEADING TO LOWERED EGG PRODUCTION ARE NOT WELL CHARACTERIZED. EGG PRODUCTION IS GOVERNED BY THE REPRODUCTIVE AXIS BUT OTHER NEUROENDOCRINE AXES CAN INFLUENCE THE ACTIVITY OF THE REPRODUCTIVE AXIS. OUR PREVIOUS RESEARCH ASSOCIATED INCREASED THYROID AXIS ACTIVITY WITH THE LOW EGG PRODUCTION PHENOTYPE, LEADING TO THE HYPOTHESIS THAT HEN EGG PRODUCTION RATES ARE REGULATED BY THYROID HORMONES. THE CURRENT PROPOSAL AIMS TO DEFINE THE REGULATORY ROLE OF THYROID HORMONE IN THE CONTROL OF EGG PRODUCTION RATES IN TURKEY HENS. OUR SPECIFIC OBJECTIVES ARE TO: 1) DEFINE THE HORMONAL PROFILES OF THE REPRODUCTIVE AND THYROID AXES IN LOW EGG PRODUCING TURKEY HENS (LEPH), AVERAGEEGG PRODUCING TURKEY HENS (AEPH), AND HIGHEGG PRODUCING TURKEY HENS (HEPH) DURING THE OPEN PERIOD; 2) DETERMINE THE INFLUENCE OF CIRCULATING THYROID HORMONE LEVELS ON THE REPRODUCTIVE AXIS DURING PEAK EGG PRODUCTION; AND 3) CHARACTERIZE PITUITARY RESPONSIVENESS TO THYROID AXIS STIMULATION IN LEPH AND HEPH. TAKEN TOGETHER THESE SPECIFIC OBJECTIVES WILL INTERROGATE THE RELATIONSHIP BETWEEN THE THYROID AND REPRODUCTIVE AXES AND THE IMPLICATION OF THIS RELATIONSHIP IN OBSERVED HEN EGG PRODUCTION RATES. COMPLETION OF THIS RESEARCH WILL PROVIDE THE POULTRY INDUSTRY WITH BIOMARKERS INDICATIVE OF EGG PRODUCTION RATES THAT CAN BE USED IN BREEDING PROGRAMS TO INCREASE HEN REPRODUCTIVE PERFORMANCE, ULTIMATELY INCREASING THE NUMBER OF POULTS PRODUCED PER HEN. IMPROVEMENTS TO HEN REPRODUCTIVE PERFORMANCE WILL INCREASE THE EFFICIENCY OF THE POULTRY INDUSTRY, UNDERPINNING MEAT PRODUCTION FOR THE GROWING HUMAN POPULATION.