SOME PROTEINS PRODUCED IN AND RELEASED BY SKELETAL MUSCLE REGULATE GROWTH OF THE MUSCLE ITSELF AND ARE REFERRED TO AS; MYOKINES. MYOKINES HAVE BEEN STUDIED IN HUMANS AND RODENTS, BUT UNDER STUDIED IN LIVESTOCK. MANY PHYSIOLOGICAL, GENETIC AND PRODUCTION ADVANCEMENTS HAVE IMPROVED THE EFFICIENCY AND RATE OF MUSCLE GROWTH IN BEEF CATTLE. THIS PROPOSAL INVESTIGATES A NEW PATH TOWARDS UNDERSTANDING THE REGULATION OF MUSCLEGROWTH, POTENTIALLY IDENTIFYING NEW NATURAL MEANS OF FURTHER IMPROVING MUSCLE GROWTH IN MEAT ANIMALS. THIS REQUIRES EVALUATION OF SEVERAL MYOKINES AT THE GENE AND PROTEIN LEVEL USING HARVESTED BOVINE MUSCLE STEMCELLS (BSCS). THE FIRST STEP IS TO CHARACTERIZE THE PATTERN OF MYOKINE RELEASE FROM CULTURED BSCS ACROSS NORMAL DEVELOPMENT AND MATURATION STAGES. STUDIES IN NON-LIVESTOCK ANIMALS INDICATE THAT MYOKINES INCREASE FOLLOWING EXERCISE AND CONTRIBUTE TO BENEFICIAL MUSCLE GROWTH ASSOCIATED WITH CONTRACTION. THE SAME MECHANISMS FOR INDUCED MUSCLE GROWTHLIKELY EXIST IN BEEF CATTLE AND MAY BE PROMOTED IN OTHER WAYS; PERHAPS EVEN NUTRITIONALLY. FURTHER, DIFFERENCES IN MYOKINE PRODUCTION IN MUSCLE CELLS FROMYOUNG CALVES VERSUS MUSCLE CELLS MID-PRODUCTION AGED CALVES, TWO IMPORTANT TIMES FOR SKELETAL MUSCLE GROWTH WILL BE ASSESSED.THIS WILL BE THE FIRST RESEARCH TO PROVIDE CATTLESPECIFIC MYOKINE EXPRESSION DATA. THEREFORE, IT WILL ADVANCE IN OUR UNDERSTANDING SKELETAL MUSCLE GROWTH IN BEEF CATTLE. THIS PROJECT WILL PROVIDE THE INSIGHT AND DATA NECESSARY FOR IMPROVEMENTS IN MUSCLE GROWTH AND EFFICIENCY IN LIVESTOCK SPECIES USING MORE COMPLETE UNDERSTANDING OF THE NATURAL PHYSIOLOGICAL REGULATION OF MUSCLE GROWTH.WE ANTICIPATE THAT THIS WILL PAVE THE WAY FOR TARGETED ASSESSMENT OF MYOKINES IN LIVE BEEF CATTLE, UNDER VARIED NUTRITIONAL INTERVENTIONS, WITHIN DIFFERENT BREEDS AND SPECIES ALL WITH THE POTENTIAL TO ENHANCE SKELETAL MUSCLE GROWTH IN MEAT PRODUCING LIVESTOCK.