?CHOLINE IS METABOLIZED IN MANY ORGANS INTO A VARIETY OF METABOLITES THAT SERVE MULTIPLE PURPOSES. PHOSPHOLIPIDS DERIVED FROM CHOLINE, SUCH AS PHOSPHATIDYLCHOLINE, PLAY A MAJOR ROLE IN LIPID TRAFFICKING. DESPITE A SIGNIFICANT OUTPUT OF LIPIDS IN THE FORM OF MILK FAT, CHOLINE METABOLISM IN THE MAMMARY GLAND IN THE CONTEXT OF MILK FAT PRODUCTION IS LARGELY UNKNOWN. DAIRY PRODUCERS STRIVE TO MAXIMIZE MILK FAT PRODUCTION AS IT IS A MAJOR DRIVER OF THE ECONOMIC VALUE OF MILK, THUS THERE IS A GREAT INTEREST TO DEVELOP STRATEGIES TO INCREASE MILK FAT PRODUCTION. TO DEVELOP SUCH STRATEGIES, IT IS NECESSARY TO HOLISTICALLY UNDERSTAND MAMMARY LIPOGENESIS AND THE FACTORS THAT AFFECT IT. THE MAJOR OBJECTIVE OF THIS PROPOSAL IS TO FURTHER OUR UNDERSTANDING OF CHOLINE METABOLISM IN THE MAMMARY GLAND IN THE CONTEXT OF MILK FAT PRODUCTION.TO COMPLETE THESE OBJECTIVES, A SERIES OF EXPERIMENTS WILL BE DONE WITH LACTATING DAIRY COWS TO ASSESS THE EFFECT OF STAGE OF LACTATION, NUTRITION, AND CHOLINE SUPPLEMENTATION ON CHOLINE METABOLISM IN THE MAMMARY GLAND AND ITS RELATIONSHIP WITH MILK FAT PRODUCTION. THE RESULTS WILL BE COMMUNICATED IN THREE MAJOR WAYS: 1) ABSTRACT PRESENTATIONS AT RELEVANT SCIENTIFIC CONFERENCES, 2) PEER-REVIEWED PUBLICATIONS IN SCIENTIFIC JOURNALS, AND 3) EXTENSION TALKS WITH PRODUCERS OF THE NORTHEAST AREA OF THE US AND FARM TOURS WITH 4H AND FFA STUDENTS AT THE PENNSYLVANIA STATE UNIVERSITY. WE EXPECT THAT THE RESULTS OF THIS RESEARCH WILL FURTHER INFORM RESEARCHERS AND NUTRITIONISTS WHEN DEVELOPING STRATEGIES TO MAXIMIZE MILK FAT PRODUCTION. FURTHERMORE, IT WILL ALSO SHED A LIGHT INTO THE IMPORTANCE OF CHOLINE METABOLISM IN THE MAMMARY GLAND IN THE CONTEXT OF MILK FAT PRODUCTION.