PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS (PRRSV) CAUSES THE MOST COSTLY DISEASE TO SWINE PRODUCTION IN THE UNITED STATES. DISEASE CAUSED BY THIS VIRUS OFTEN INVOLVES SECONDARY BACTERIAL PATHOGENS, WHICH EXACERBATES RESPIRATORY DISEASE AND INCREASES ANTIMICROBIAL ADMINISTRATION IN YOUNG GROWING PIGS. ALTHOUGH COMMERCIAL VACCINES ARE USED TO REDUCE THE EFFECTS OF PRRSV ON SWINE HEALTH, THE CURRENTLY AVAILABLE VACCINES ARE CONSIDERED INADEQUATE FOR DISEASE CONTROL. ALTERNATIVE STRATEGIES FOR CONTROL OF PRRSV IS NEEDED TO MAINTAIN SWINE HEALTH AND WELFARE WHILE LESSENING THE ECONOMIC EFFECTS OF THIS DISEASE ON PORK PRODUCERS. THE GOAL OF THIS WORK IS TO INVESTIGATE THE GUT MICROBIOME AS AN ALTERNATIVE TOOL FOR PRRSV CONTROL DUE TO ITS IMPACT ON THE IMMUNE SYSTEM AND OUTCOME AFTER INFECTION. OBJECTIVES OF THE WORK INCLUDE INVESTIGATING THE EFFECTS OF MICROBIOME MODULATION ON OUTCOME OF SWINE WITH RESPIRATORY DISEASE AND IDENTIFYING WHAT BENEFICIAL MICROBES ARE ASSOCIATED WITH IMPROVED HEALTH. WE ANTICIPATE THE DATA GENERATED IN THIS PROJECT WILL ALLOW US TO CHARACTERIZE AND DETERMINE THE GUT MICROBES WHICH IMPROVE PIG HEALTH IN THE PRESENCE OF PRRSV. OUR GOAL IS TO DETERMINE HOW BENEFICIAL GUT MICROBES MAY BE USED AS A PREVENTATIVE MEDICINE TOOL TO REDUCE THE EFFECTS OF RESPIRATORY DISEASE AND DECREASE THE NEED FOR ANTIMICROBIALS IN SWINE. THE IMPACTS OF THIS WORK WILL IMPROVE ANIMAL WELFARE AND ANIMAL HEALTH, LESSEN THE ECONOMIC LOSSES TO PRODUCERS ASSOCIATED WITH PRRSV, AND REDUCE THE RISK OF ANTIMICROBIAL RESISTANCE IN SWINE.