1. WHAT IS THE CURRENT PROBLEM? THE PROJECT DIRECTORS (PDS) HAVE CONDUCTED A NUMBER OF STUDIES DOCUMENTING THE DIFFERENCES IN GROWTH AND METABOLISM BETWEEN MARBLING AND OTHER CARCASS FAT DEPOTS IN BEEF CATTLE. THE MAIN GOAL OF THE PDS HAS BEEN TO INCREASE THE PROFITABILITY OF BEEF CATTLE BY INCREASING BEEF CARCASS QUALITY GRADE (IN OTHER WORDS, INCREASE MARBLING), WITHOUT INCREASING OVERALL CARCASS FATNESS. HOWEVER, OVER 30 YEARS OF RESEARCH HAS NOT PROVIDED SUFFICIENT INSIGHT INTO DIFFERENCES BETWEEN MARBLING AND CARCASS FAT DEPOTS TO ALLOW FOR THE MORE EFFICIENT PRODUCTION OF MARBLING WITHOUT ALSO EXACERBATING CARCASS FATNESS. AN INCREASED UNDERSTANDING OF KEY DIFFERENCES BETWEEN MARBLING AND CARCASS FAT COULD ALLOW FOR SPECIFIC TECHNOLOGIES TO BE DEVELOPED THAT WOULD INCREASE MARBLING WITHOUT ALSO INCREASING CARCASS FATNESS.2. WHAT BASIC METHODS AND APPROACHES WILL BE USED TO COLLECT AND PRODUCE DATA/RESULTS AND SUBSEQUENTLY INFORM TARGET AUDIENCES? CATTLE PRODUCE LIPID (FAT) FROMACETATE AND GLUCOSE, AND OLEIC ACID IS PRODUCED IN HIGH AMOUNTS IN MARBLING OF CATTLE FED CORN-BASED DIETS. INCREASING THE AMOUNT OF OLEIC ACID IN MARBLING IMPROVES THE OVERALL PALATABILITY OF BEEF, AND THE PDS HAVE DOCUMENTED THAT BEEF HIGH IN OLEIC ACID REDUCES RISK FACTORS FOR CARDIOVASCULAR DISEASE IN MEN AND WOMEN. IN THIS PROJECT, WE WILL TEST HOW ACETATE AND OLEIC INTERACT TO PROMOTE AN INCREASE IN MARBLING IN BEEF CATTLE.SOURCES OF MARBLING AND SUBCUTANEOUS FAT. ANGUS CROSSBRED STEER CALVES WILL BE WEANED AT 8 MONTHS OF AGE AND THEN FED A CORN-BASED FEEDLOT DIET DESIGNED TO INCREASE THE AMOUNT OF MARBLING IN THEIR MUSCLES. STEERS WILL BE SLAUGHTERED AT 12, 16, AND 20 MONTHS OF AGE (8 FOR EACH AGE GROUP). WE ESTIMATE THE CATTLE WILL GRADE USDA SELECT, LOW CHOICE, AND HIGH CHOICE AT 12, 16, AND 20 MONTHS OF AGE, RESPECTIVELY.LABORATORY ACTIVITIES. WE WILL OBTAIN MARBLING AND SUBCUTANEOUS FAT FROM THE STEERS IMMEDIATELY AFTER SLAUGHTER (AT WHICH TIME THE MARBLING AND SUBCUTANEOUSFAT ARE STILL LIVING AND VIABLE). IN THE LABORATORY, WE WILL TEST THE EFFECTS OF COMPOUNDS PRODUCED BY CATTLE AND COMMON IN THE BLOOD STREAM (ESPECIALLY ACETATE AND OLEIC ACID) ON LIPID ACCUMULATION IN MARBLING AND SUBCUTANEOUS FAT. LABORATORY ANALYSES WILL INCLUDE MEASUREMENTS OF A NUMBER OF BIOCHEMICAL COMPOUNDS THAT ARE RELATED TO MARBLING AND SUBCUTANEOUS FAT GROWTH. WE PREDICT THAT OLEIC ACID WILL HAVE THE GREATEST EFFECT ON PROMOTING LIPID ACCUMULATION IN MARBLING FROM THE HIGH CHOICE STEERS.3. WHAT ULTIMATE GOALS DOES THE PROJECT HOPE TO ACHIEVE? A GOAL OF THIS PROJECT IS TO SUSTAIN THE ECONOMIC VIABILITY OF FARM OPERATIONS, AND TO ENHANCE THE QUALITY OF LIFE FOR FARMERS. MANY FARM OPERATIONS IN THE U.S. ARE BARELY PROFITABLE, AND PRODUCERS ARE SEEKING PRACTICAL MEANS BY WHICH TO INCREASE THE VALUE OF THEIR BEEF CATTLE. IF COW/CALF PRODUCERS AND/OR BEEF CATTLE FEEDLOT SYSTEMS CONSISTENTLY PRODUCE CATTLE THAT WILL GRADE IN THE UPPER RANGE OF QUALITY GRADES, THEN THIS WILL PROVIDE THE OPPORTUNITY FOR THEM TO TARGET BRANDED BEEF PROGRAMS, DIRECTLY BENEFITING THEIR BEEF CATTLE OPERATIONS BY INCREASING BEEF CARCASS VALUE. THE SUCCESSFUL ACCOMPLISHMENT OF THE GOALS OF THE PROJECT WILL PROVIDE INFORMATION ABOUT A NOVEL MECHANISM BY WHICH THE GPR43 RECEPTOR INCREASES MARBLING IN BEEF CATTLE. IF ACTIVATION OF THE GPR43 BY OLEIC ACID TRULY INCREASES MARBLING ACCUMULATION, THEN THIS RESEARCH COULD LEAD TO DIFFERENT NUTRITIONAL STRATEGIES THAT WOULD INCREASE OLEIC ACID INTAKE FROM THE DIET AND/OR INCREASE THE ENDOGENOUS PRODUCTION OF OLEIC ACID BY MARBLING. AN INCREASED UNDERSTANDING OF THE DIFFERENCES BETWEEN MARBLING AND OTHER CARCASS FAT DEPOTS WOULD ALLOW FOR SPECIFIC TECHNOLOGIES TO BE DEVELOPED TO INCREASE MARBLING, CONCOMITANTLY INCREASING CARCASS QUALITY AND THEREFORE VALUE OF BEEF AND BEEF PRODUCTS. IF WE CAN CONFIRM THAT MARBLING HAS DIFFERENT RESPONSES TO OLEIC ACID THAN OTHER CARCASS FAT DEPOTS, THEN THIS WILL ALLOW PRODUCERS FOR THE FIRST TIME TO SPECIFICALLY TARGET INCREASES IN MARBLING WHILE NOT INCREASING CARCASS FATNESS IN BEEF CATTLE. THIS WOULD DIRECTLY IMPACT THE SUSTAINABILITY AND PROFITABILITY OF ANIMAL AGRICULTURE IN THE U.S. BY PROVIDING A UNIQUE MECHANISM BY WHICH CARCASS QUALITY COULD BE IMPROVED.