PROFITS FROM BEEF PRODUCTION IN GREAT PLAINS FEEDLOTS ARE INCREASINGLY OFFSET BY HEALTH ISSUES. IN THE PAST DECADE, IT WAS OBSERVED THAT FAT-CATTLE CAN SUFFER FROM PULMONARY HYPERTENSION, A BUILDUP IN BLOOD PRESSURE BETWEEN THE HEART AND LUNGS. ALSO, IT IS VERY CONCERNING THAT THIS CONDITION MAY BE MADE WORSE IF AN ANIMAL CONTRACTS A RESPIRATORY DISEASE, ESPECIALLY LATE IN THE FATTENING PHASE. THE PROJECT WILL FOCUS STUDY ON FATTENING ANGUS STEERS, WITH AND WITHOUT PULMONARY HYPERTENSION, AND THEN EVALUATE THE IMPACT OF VIRAL INFECTION IN THE CATTLE SUFFERING FROM THE CONDITION. MORE SPECIFICALLY, THESE STUDIES WILL EVALUATE HOW HIGH-PRESSURE BETWEEN THE HEART AND LUNGS IN FATTENING STEERS INFLUENCES HEART AND LUNG TISSUES, THE IMMUNE SYSTEM, AND OVERALL BEHAVIOR; SPECIFICALLY, ELECTRONIC DATA SYSTEMS WILL RECORD ACTIVITY AND FEED INTAKE OF HEALTHY AND CATTLE SUFFERING FROM HIGH-PRESSURE BETWEEN THE HEART AND LUNGS AND INFECTED WITH A RESPIRATORY VIRUS.PULMONARY HYPERTENSION (PH) APPEARS TO BE RESPONSIBLE FOR FATTENING-INDUCED CHANGES IN THE LEFT-SIDE OF THE HEART, WHICH IS A SLIGHTLY DIFFERENT OUTCOME THAN OBSERVED IN CATTLE SUFFERING FROM LACK OF OXYGEN BECAUSE OF HIGH MOUNTAIN (I.E., BRISKET-RIGHT HEART) DISEASE. WE HYPOTHESIZE THAT INFLAMMATION COMBINED WITH ELEVATED METABOLIC DEMAND FROM FATTENING CONTRIBUTE TO LOW OXYGEN IN BLOOD AND DEVELOPMENT OF PH IN FEEDLOT CATTLE AT LOW ELEVATION. USING FATTENED ANGUS STEERS WEANED FROM LOW ELEVATION COW-CALF OPERATIONS, WE WILL EXECUTE THESE SPECIFIC AIMS: 1) UTILIZE MARKER MOLECULES IN BLOOD TO EVALUATE THE CONSEQUENCES OF PH; 2) UTILIZE THESE MARKER MOLECULES TO ASSESS INFLAMMATION AND LOW OXYGEN DELIVERY IN HEART AND LUNGS; AND 3) DETERMINE THE INFLUENCE OF PH ON (A) CATTLE BEHAVIOR AND PERFORMANCE CHARACTERISTICS, AND (B) THE RESPONSE TO EXPERIMENTAL INFECTION WITH BOVINE RESPIRATORY SYNCYTIAL VIRUS, A COMMON PATHOGEN OF CATTLE THAT CAUSES RESPIRATORY DISEASE. THIS RESEARCH WILL IDENTIFY BLOOD MARKERS THAT PREDICT DISEASE RISK TO BENEFIT SELECTIVE BREEDING, PRE-CONDITIONING, AND FATTENING PROGRAMS, LEADING TO IMPROVED CATTLE HEALTH.