** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** IN MODERN BROILERS, THE FIRST WEEK POST-HATCH IS ASSOCIATED WITH RAPID MUSCLE GROWTH AND REPRESENTS ALMOST 20-25% OF THE TOTAL PRODUCTION PERIOD. HENCE, ANY NUTRIENT AND ENERGY LIMITATIONS DURING THIS CRITICAL PHASE, SUCH AS EXPERIENCED DURING POST-HATCH FEED DEPRIVATION, CAN LIMIT MUSCLE GROWTH AND OVERALL PRODUCTIVITY. TOWARDS THIS, EARLY NUTRITIONAL SUPPLEMENTATION VIA IN-OVO FEEDING WAS IDENTIFIED AS A POTENTIAL APPROACH TO JUMP-START DEVELOPMENT IN CHICKS. ALONG THESE LINES, ALTHOUGH WIDELY USED AS A GROWTH PROMOTER, PROBIOTICS HAVE NOT BEEN EVALUATED AS AN IN-OVO INTERVENTION TO MINIMIZE THE DEFICIENCIES CAUSED BY DELAYED FEED ACCESS. IN THIS REGARD, DATA FROM A SYNERGISTIC USDA GRANT DEMONSTRATE THAT IN-OVO SPRAY APPLICATION OF PROBIOTICS PROMOTED EMBRYONIC GROWTH, ENERGY RESERVES IN THE PERINATAL EMBRYO AND POST-HATCH PERFORMANCE. FURTHER, PRELIMINARY OBSERVATIONS INDICATE A ROLE FOR PROBIOTICS IN PROMOTING MUSCLE DEVELOPMENT INCLUDING SATELLITE CELL ACTIVITY, MYOFIBER HYPERTROPHY AND MUSCLE GROWTH IN CHICKS SUBJECT TO DELAYED FEED ACCESS. HOWEVER, THIS WARRANTS FURTHER INVESTIGATION. THEREFORE, AS A NEXT STEP, THE PROPOSED RESEARCH AIMS TO DETERMINE THE EFFECTS OF IN-OVO PROBIOTIC SUPPLEMENTATION ON MUCLE DEVELOPMENT IN CHICKS SUBJECT TO POST-HATCH FEED DEPRIVATION AND ELUCIDATE THE UNDERLYING MOLECULAR MECHANISMS. ULTIMATELY, WE EXPECT THAT IN-OVO PROBIOTIC APPLICATION CAN BE INTEGRATED WITH ROUTINE MANAGEMENT PRACTICES TO ACHIEVE OPTIMAL MUSCLE GROWTH AND SUBSEQUENT MEAT PRODUCTION IN BROILERS, THEREBY PROMOTING THE POULTRY INDUSTRY.