** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** INCREASING THE AMOUNT AND EFFICIENCY OF CHICKEN MEAT PRODUCTION IS IMPORTANT TO THE POULTRY INDUSTRY AND TO THE GROWING WORLD POPULATION. GROWTH IN CHICKENS IS CONTROLLED IN PART BY THE CHICKEN'S PRODUCTION OF ITS OWN HORMONES, INCLUDING GROWTH HORMONE (GH) WHICH IS SECRETED FROM THE CHICKEN'S PITUITARY GLAND. A BETTER UNDERSTANDING OF THE MECHANISMS REGULATING GH SECRETION IS ESSENTIAL TO DEVELOP GENETIC MARKERS FOR IMPROVING GROWTH PERFORMANCE IN BROILER CHICKENS. WE REPORTED THAT TREATMENT WITH THE ADRENAL GLUCOCORTICOID HORMONE CORTICOSTERONE (CORT) CAN INDUCE GH PRODUCTION DURING CHICKEN EMBRYONIC DEVELOPMENT. WE SHOWED THAT PREMATURE INDUCTION OF GH IS ASSOCIATED WITH IMPROVED GROWTH RATES OF CHICKENS AFTER HATCH. FUTURE SELECTION OF BREEDING STOCK BASED ON MARKERS WITHIN THE CORTICOTROPIC, THYROTROPIC, AND SOMATOTROPIC AXES HAS POTENTIAL FOR IMPROVING GROWTH AND FEED EFFICIENCY THROUGH MODULATING ENDOGENOUS CORT, T3, AND GH PRODUCTION AND THEIR TARGET TISSUE RESPONSES. HOWEVER, THE BROADER EFFECTS OF EMBRYONIC CORT AND GH ON POST-HATCH METABOLISM AND GENE EXPRESSION WITHIN THE SOMATOTROPIC, CORTICOTROPIC, AND THYROTROPIC AXES ARE NOT KNOWN. FURTHERMORE, WE HAVE YET TO DEFINE ALL OF THE TRANSCRIPTION FACTORS REQUIRED FOR CORT INDUCTION OF GH DURING EMBRYONIC DEVELOPMENT.THE SPECIFIC AIMS OF THIS PROPOSAL ARE TO: (1)DETERMINE EFFECTS OF IN OVO ADMINISTRATION OF CORT ON PRODUCTION OF THE MAJOR HORMONES THAT REGULATE GROWTH IN CHICKENS; (2)DEFINE EFFECTS OF EMBRYONIC CORT TREATMENT AND PREMATURE INDUCTION OF GH ON INDICATORS OF ADIPOSE TISSUE FUNCTION DURING POSTHATCH DEVELOPMENT; AND (3)IDENTIFY NOVEL REGULATORY ELEMENTS UPSTREAM OF THE GH GENE AND THEIR TRANSCRIPTION FACTOR PROTEINS. WE ARE NOT ADVOCATING FOR THE USE OF HORMONES IN BROILER PRODUCTION. RATHER, WE ARE STUDYING HOW HORMONES REGULATE GROWTH AND EFFICIENCY IN BROILER CHICKENS AND THE GENES INVOLVED IN THIS NORMAL PROCESS. COMPLETION OF THIS RESEARCH WILL LEAD TO NEW INFORMATION AND THE IDENTIFICATION OF GENES INVOLVED IN CONTROLLING GROWTH AND EFFICIENCY IN BROILER CHICKENS THAT CAN BE USED TO REFINE GENETIC MARKERS FOR ANIMAL SELECTION IN BROILER BREEDING PROGRAMS FOR THE POULTRY INDUSTRY TO PRODUCE MORE FOOD MORE EFFICIENTLY FOR THE GROWING WORLD'S POPULATION.