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