SKELETAL PROBLEMS, EXCESS FAT ACCUMULATION AND MUSCLE ABNORMALITIES ARE IMPORTANT ECONOMIC, HEALTH AND WELFARE ISSUES FOR THE POULTRY INDUSTRY. RAPID GROWTH IN BROILERS CAUSES BONE DISORDERS, MUSCLE DEGENERATION (MYOPATHY), AND FAT FORMATION IN ABDOMINAL, INTRAMUSCULAR AND BONE MARROW AREAS. THE CURRENT APPROACHES OF REDUCING SKELETAL, MUSCULAR, AND EXCESS FAT ISSUES ARE THROUGH NUTRITION STRATEGIES AND GENETIC SELECTION. WE IDENTIFIED CERTAIN OXIDIZED CHOLESTEROL METABOLITES SUCH AS 20S OXYSTEROL ARE POTENTIAL BIOACTIVE MOLECULES TO PROMOTE BONE AND MUSCLE GROWTH AND REDUCE FAT FORMATION. THUS, THE OVERALL HYPOTHESIS IS THAT 20S OXYSTEROL WILL ENHANCE BONE FORMATION AND MUSCLE DEVELOPMENT AND REDUCE FAT FORMATION BY REGULATING CELL DIFFERENTIATION. THERE ARE THREE SPECIFIC OBJECTIVES: 1) TO DETERMINE THE PRO-MYOGENIC MECHANISM OF 20S OXYSTEROL IN CHICKENS; 2) TO DETERMINE OPTIMAL DOSAGE AND TIMING OF 20S OXYSTEROL IN OVO INJECTION; AND 3) TO DETERMINE THE LONG-TERM EFFECTS OF 20S OXYSTEROL ON GROWTH PERFORMANCE, BONE/MUSCLE FORMATION, CARCASS YIELD, AND FEED EFFICIENCY. WE ANTICIPATE THAT 20S OXYSTEROL WILL STIMULATE BONE GROWTH AND MUSCLE DEVELOPMENT AND MINIMIZE FAT FORMATION, IMPROVING SKELETAL HEALTH, LEAN MEAT PRODUCTION AND FEED EFFICIENCY IN BROILERS. THE OUTCOMES OF THIS PROJECT WILL PROVIDE A NOVEL STRATEGY TO IMPROVE WELFARE CONDITIONS, MEAT-QUALITY, AND FEED NUTRIENT UTILIZATION, REDUCING PRODUCTION COST AND ECONOMIC LOSS, INCREASING PROFITS FOR THE POULTRY INDUSTRY, AND MAKING THE POULTRY INDUSTRY MORE SUSTAINABLE.