RATIONALE:ESTABLISHING A HEALTHY AND EFFICIENT GUT MICROBIOME EARLY IN LIFE PLAYS A CRITICAL ROLE IN DETERMINING LONG-TERM ANIMAL PERFORMANCE AND PRODUCTIVITY. THE PREWEANING PERIOD IN DAIRY CALVES PRESENTS A UNIQUE OPPORTUNITY TO GUIDE MICROBIAL DEVELOPMENT IN WAYS THAT SUPPORT GROWTH, FEED EFFICIENCY, AND DIGESTIVE HEALTH THROUGHOUT LIFE. THIS PROJECT EXPLORES THE USE OF TARGETED PROBIOTIC SUPPLEMENTS, CULTURED FROM NATURAL GUT COMMENSALS OF PREWEANED CALVES, TO IMPROVE MICROBIAL COLONIZATION PATTERNS. THE GOAL IS TO ENHANCE CALF PERFORMANCE BY PROMOTING BENEFICIAL FERMENTATION PATHWAYS AND REDUCING COLONIZATION BY LESS DESIRABLE MICROBIAL POPULATIONS. FINDINGS FROM THIS STUDY WILL PROVIDE VALUABLE INSIGHT INTO THE POTENTIAL OF EARLY-LIFE MICROBIAL INTERVENTIONS TO IMPROVE OVERALL ANIMAL HEALTH AND PRODUCTIVITY IN DAIRY SYSTEMS.HYPOTHESIS:THIS PROJECT HYPOTHESIZES THAT NEONATAL SUPPLEMENTATION WITH SPECIFIC PROBIOTIC BACTERIAL ISOLATES ADMINISTERED ALONE OR IN COMBINATION WITH SELECTED DIETARY ADDITIVES--WILL PROMOTE STABLE, BENEFICIAL MICROBIAL COLONIZATION AND FERMENTATION PATTERNS IN THE DEVELOPING RUMEN. SPECIFICALLY, WE PROPOSE THAT STIMULATING ACETATE-DEPENDENT BUTYRATE SYNTHESIS WILL ENHANCE MICROBIAL HYDROGEN UTILIZATION EFFICIENCY, SUPPORT BETTER NUTRIENT CONVERSION, AND SUPPRESS COLONIZATION BY COMPETING MICROBIAL GROUPS. THESE MICROBIAL SHIFTS ARE EXPECTED TO LEAD TO MEASURABLE IMPROVEMENTS IN GROWTH, RUMEN DEVELOPMENT, AND LONG-TERM PERFORMANCE.SPECIFIC AIMS/OBJECTIVES:OBJECTIVE 1: EVALUATE THE ORAL ADMINISTRATION OF FAECALIBACTERIUM SPP. AND OTHER PROBIOTICS IN DAIRY CALVES. THIS OBJECTIVE WILL ASSESS COLONIZATION POTENTIAL, IMPACTS ON RUMEN AND GUT MICROBIAL PROFILES, AND EFFECTS ON CALF GROWTH AND HEALTH DURING THE PREWEANING PHASE AND AT ONE YEAR OF AGE.OBJECTIVE 2: USE IN VITRO FERMENTATION SYSTEMS TO DETERMINE THE EXTENT TO WHICH MICROBIAL COMMUNITY DYNAMICS AND FERMENTATION PATTERNS CAN BE INFLUENCED BY COMBINING THE PROBIOTIC COCKTAIL WITH SELECTED DIETARY ADDITIVES (E.G., 3-NOP, SEAWEED BLENDS, CHLOROFORM). THESE ASSAYS WILL MEASURE CHANGES IN HYDROGEN FLUX, FERMENTATION END PRODUCTS, AND MICROBIAL COMPETITION.OBJECTIVE 3: IDENTIFY THE MOST EFFECTIVE COMBINATIONS OF PROBIOTIC AND DIETARY STRATEGIES THAT PROMOTE ACETATE-DEPENDENT BUTYRATE SYNTHESIS AND BENEFICIAL MICROBIAL REMODELING IN THE RUMEN, WITH THE GOAL OF SUPPORTING SUSTAINED IMPROVEMENTS IN GROWTH, FEED EFFICIENCY, AND ANIMAL HEALTH.EXPECTED RESULTS:THIS PROJECT AIMS TO ACHIEVE THREE MAIN OUTCOMES: EARLY-LIFE ADMINISTRATION OF TARGETED PROBIOTICS CAN PROMOTE BENEFICIAL MICROBIAL COLONIZATION; ACETATE-DEPENDENT BUTYRATE PRODUCTION CAN BE ENHANCED, IMPROVING ENERGY AVAILABILITY AND RUMEN FUNCTION; LONG-TERM IMPROVEMENTS IN ANIMAL PERFORMANCE AND DIGESTIVE EFFICIENCY CAN BE ACHIEVED THROUGH EARLY MICROBIAL PROGRAMMING.ANTICIPATED IMPACT:THIS WORK WILL PROVIDE EVIDENCE-BASED STRATEGIES FOR OPTIMIZING MICROBIAL DEVELOPMENT IN DAIRY CALVES DURING A CRITICAL EARLY-LIFE WI,NDOW. THE ANTICIPATED BENEFITS INCLUDE IMPROVED FEED EFFICIENCY, GROWTH, AND OVERALL ANIMAL HEALTH. BY ADVANCING PRACTICAL TOOLS FOR PRODUCERS TO INFLUENCE GUT HEALTH FROM THE START, THIS PROJECT SUPPORTS THE LONG-TERM SUSTAINABILITY AND PRODUCTIVITY OF MODERN DAIRY OPERATIONS.