AT REPRODUCTIVE MATURITY, FEMALE RAINBOW TROUT PRODUCE GREATER THAN 3,000 EGGS, EACH CONTAINING A COPY OF HER DNA. REGIONS OF THIS DNA ARE METHYLATED, A PROCESS CALLED EPIGENETIC MODIFICATION, THAT CAN REGULATE GENE EXPRESSION IN THE OFFSPRING AND AFFECT RATES OF DEVELOPMENT AND GROWTH PERFORMANCE. DIETARY INGREDIENTS SUCH AS METHIONINE AND CHOLINE ARE KEY COMPONENTS OF DNA METHYLATION PROCESS BUT THESE NUTRIENTS ARE LOW IN COMMERCIAL AQUAFEEDS CONTAINING HIGH LEVELS OF SUSTAINABLE PLANT PROTEINS. WHILE AQUAFEEDS ARE SUPPLEMENTED WITH FREE-METHIONINE TO PREVENT A NUTRITIONAL DEFICIENCY, CHOLINE IS OFTEN NOT ADDED WHICH MAY LIMIT THE CAPACITY FOR MATERNAL IMPRINTING, OR THE ABILITY OF THE FEMALE BROODSTOCK TO PASS EPIGENETIC MODIFICATIONS TO OFFSPRING. EPIGENETIC REGULATION OF GENE EXPRESSION IN FISH IS POORLY UNDERSTOOD AND THE POTENTIAL TO IMPROVE OFFSPRING GROWTH THROUGH MATERNAL IMPRINTING STRATEGIES, SUCH AS THOSE INDUCED THROUGH DIETARY INTERVENTION, HAS RECEIVED LITTLE ATTENTION. HOWEVER, RESULTS FROM OUR RECENT STUDY SUPPORTS THAT THESE STRATEGIES MAY BE FEASIBLE FOR IMPROVING GROWTH PERFORMANCE IN RAINBOW TROUT.THIS PROJECT WILL TEST THE OVERARCHING HYPOTHESIS THAT SPECIFIC DIETARY NUTRIENTS, METHYL DONORS, CAN BE SUPPLEMENTED TO FEMALE RAINBOW TROUT BROODSTOCK TO ENHANCE GROWTH PERFORMANCE IN OFFSPRING VIA EPIGENETIC MODULATION. TO ACCOMPLISH THIS, WE WILL CONDUCT THE FOLLOWING OBJECTIVES: 1) IDENTIFY HOW CHOLINE LEVELS IN RAINBOW TROUT BROODSTOCK DIETS AFFECT GROWTH AND FILLET YIELD IN THE NEXT GENERATION; 2) DETERMINE IF INCREASED CHOLINE CONCENTRATIONS IN RAINBOW TROUT EGGS AFFECT FRY PERFORMANCE; AND 3) IDENTIFY HOW CHOLINE AFFECTS PHYSIOLOGICAL AND METABOLIC PATHWAYS IN RAINBOW TROUT LIVER AND MUSCLE CELLS. THESE OBJECTIVES BUILD ON RECENT FINDINGS INDICATING THAT SUPPLEMENTING A COMMERCIAL BROODSTOCK DIET WITH CHOLINE INCREASED BODY WEIGHT IN OFFSPRING BY APPROXIMATELY 17%. THIS PROJECT WILL IDENTIFY, THROUGH "BIG DATA" APPROACHES, MECHANISMS OF GENETIC, GENOMIC, AND NUTRITIONAL INTERACTIONS THAT IMPROVE OFFSPRING PERFORMANCE. IN ADDITION, TREATING THE EGGS DIRECTLY WILL ELIMINATE EFFECTS OF MATERNAL IMPRINTING, DETERMINING THE EXTENT TO WHICH INCREASED CHOLINE LEVELS IN YOLK PROVIDES BETTER NUTRITION TO THE DEVELOPING EMBRYO AND SACFRY. THIS APPROACH WILL IDENTIFY THE PROMINENT MECHANISM (IE: EPIGENETIC MODIFICATION VERSUS IMPROVED YOLK NUTRITION) DRIVING THE OFFSPRING GROWTH RESPONSE. OVERALL, THIS PROJECT WILL ESTABLISH THAT BROODSTOCK NUTRITION STRATEGIES CAN HAVE BENEFICIAL AND PERMANENT EFFECTS ON OFFSPRING GROWTH PERFORMANCE AND INTRODUCES A NOVEL MANAGEMENT APPROACH FOR IMPROVING AQUACULTURE PRODUCTION CAPACITY (INDUSTRY PROGRESSION). AN ANTICIPATED IMPACT OF THIS PROJECT IS IDENTIFYING THE BENEFITS OF CHOLINE-SUPPLEMENTATION FOR BROODSTOCK DIETS, A STRATEGY THAT CAN BE EASILY ADOPTED BY AQUAFEED MANUFACTUERS. IN ADDITION, THIS PROJECT WILL IDENTIFY EPIGENETIC AND TRANSCRIPTOMIC SIGNATURES INDICATIVE OF MATERNAL IMPRINTINGTHAT WILL LEAD TO IDENTIFYING CANDIDATE BIO-MARKERS CENTRAL FOR REFINING NUTRITIONAL STRATEGIES THAT EXPLOIT THESE MECHANISMS (SCIENTIFIC ADVANCEMENT).