NUTRITIONAL MANAGEMENT OF PREGNANT FEMALES IN THE BEEF COW HERD CAN HAVE DIRECT INFLUENCES ON THE DEVELOPMENT AND PERFORMANCE OF THEIR OFFSPRING THROUGHOUT THEIR POST-NATAL LIVES. COW HERDS OFTEN EXPERIENCE DRAMATIC CHANGES IN QUALITY AND QUANTITY OF AVAILABLE FORAGES AS THE SEASONS TRANSITION FROM FALL INTO WINTER; A TIME DURING WHICH A MAJORITY OF COWS IN THE US ARE IN MID-GESTATION. PROVIDING PROTEIN/ENERGY SUPPLEMENTS DURING MID-GESTATION CAN BE BENEFICIAL FOR MEETING REQUIREMENTS OF BOTH THE DAM AND THE DEVELOPING CALF. IN ADDITION, GROWTH RATES AFTER WEANING OF CALVES CAN ALTER GROWTH PERFORMANCE, CARCASS CHARACTERISTICS, AND SEMEN QUALITY.HOWEVER, THE INDIVIDUAL AND INTERACTIVE EFFECTS OF PRE-NATAL AND POST-WEANING NUTRITION ON BULL CALF METABOLISM, GROWTH, AND REPRODUCTIVE CHARACTERISTICS REMAINS UNEXPLORED. WE HYPOTHESIZE THAT MATERNAL NUTRITION DURING PREGNANCY AND DIFFERING POST-WEANING PLANES OF NUTRITION WILL IMPACT OFFSPRING GROWTH AND REPRODUCTIVE CHARACTERISTICS. OUR SPECIFIC OBJECTIVES ARE TO EVALUATE THE INDIVIDUAL AND INTERACTIVE IMPACTS OF PRE-NATAL AND POST-WEANING NUTRITION IN BULL CALVES ON SEMEN PRODUCTION AND QUALITY, TESTICULAR CHARACTERISTICS, FEED AND GROWTH EFFICIENCY, CARCASS COMPOSITION, SKELETAL MUSCLE CHARACTERISTICS, METABOLIC PHENOTYPE, AND TRANSCRIPTOMIC PROFILES OF TESTICULAR PARENCHYMA. WE ANTICIPATE THAT THAT BULL CALF GROWTH AND METABOLISM, SKELETAL MUSCLE, AND GAMETE FORMATION AND FUNCTION WILL BE IMPACTED BY PRE-NATAL AND POST-WEANING DIETARY TREATMENTS. THESE OBSERVATIONS WILL UNCOVER THE LONG-TERM IMPLICATIONS OF PRE-NATAL MANAGEMENT OF PREGNANT BEEF HEIFERS AND POST-WEANING MANAGEMENT OF MALE OFFSPRING TO ENHANCE BEEF PRODUCER PROFITABILITY THROUGH THE INCREASED GAIN, FEED EFFICIENCY, AND SEMEN QUALITY. PROJECT RESULTS WILL ALSO POSE CRITICAL QUESTIONS AND PROVIDE SAMPLES FOR FUTURE RESEARCH EFFORTS TO UNDERSTAND HOW THE INFLUENCE OF PRE- AND POST-NATAL NUTRITION IN BULLS CAN EXTEND TO IMPACT PRODUCTION EFFICIENCIES THROUGH MULTIPLE FUTURE GENERATIONS.