THE GOAL FOR THE U.S. FOOD SYSTEM IS TO PROVIDE ACCESS TO AFFORDABLE AND NUTRITIOUS FOOD. FOR FOOD ANIMAL PRODUCTION SYSTEMS THIS MEANS REARING HEALTHY ANIMALS AND MANAGING INPUT COSTS. ANTIBIOTICS ARE A TOOL OFTEN USED TO CONTROL HEALTH ISSUES SUCH AS NEONATAL CALF GASTROINTESTINAL (GI) DISEASE, WHICH REMAINS ONE OF THE MOST PROBLEMATIC DISEASES IN DAIRY CALVES. HOWEVER, ANALYTIC ACCURACY OF GI DISEASE PHENOTYPES AND PRUDENT USE OF ANTIBIOTICS ARE HINDERED BY LIMITED DIAGNOSTICS AND FEW POSTMORTEM EVALUATIONS. THIS PROJECT'S OBJECTIVES ADDRESS THESE LIMITATIONS BY DELINEATING DAIRY CALF GI DISEASE PHENOTYPES, APPLYING AND EVALUATING FECAL MICROBIOTA TRANSPLANTS (FMT) FOR THE TREATMENT OF GI DISEASES AS AN ALTERNATIVE TO ANTIBIOTIC USE, AND GENERATING AND DISSEMINATING INFORMATION REGARDING ENHANCED DIAGNOSTIC AND THERAPEUTIC OPTIONS FOR NEONATAL DAIRY CALF GI DISEASE. SPECIFICALLY, DAIRY CALF GI DISEASE GRADIENTS WILL BE ASSESSED BASED ON MODIFICATIONS IN FECAL MICROBIOTAS, INTERLEUKIN-6 LEVELS, GI EPITHELIAL CELL GENE EXPRESSION, AND PATHOLOGIC OUTCOMES. THE INTEGRATION OF THESE PARAMETERS WILL INFORM NOVEL PHENOTYPIC CLASSIFICATIONS OF GI DISEASE AND ALLOW FOR THE DEVELOPMENT AND ASSESSMENT OF THERAPEUTIC FMT. THE SUCCESS OF THIS STUDY WILL BE WITHIN THE DISSEMINATION OF APPLICABLE KNOWLEDGE TO RELEVANT STAKEHOLDERS INCLUDING FOOD ANIMAL PRACTITIONERS. WE WILL CREATE AND DELIVER AN EXTENSION PROGRAM ADDRESSING NEONATAL CALF MANAGEMENT, INCLUDING DIAGNOSTIC OVERSIGHT, THERAPEUTIC ALTERNATIVES TO ANTIBIOTIC USE, AND IMPACTS OF DISEASE. THESE OUTCOMES ALIGN WITH THE MISSION OF CROSSCUTTING PROGRAM A1701 TO SUPPORT FARM EFFICIENCY, PROFITABILITY, AND SUSTAINABILITY WHILE MITIGATING CONSTRAINTS ON FOOD PRODUCTION.