** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** EXCESSIVE LIPOLYSIS (I.E. FAT BREAKDOWN) DURING THE TRANSITION PERIOD IN DAIRY COWS IS ASSOCIATED WITH INCREASED DISEASE SUSCEPTIBILITY AND CELLULAR DAMAGE WITHIN THE ADIPOSE TISSUE. SUPPLEMENTING COWS WITH OLEIC ACID DURING THE EARLY LACTATION PERIOD REDUCES BODY WEIGHT AND BODY CONDITION SCORE LOSSES. THIS SUGGESTS THAT OLEIC ACID FAVORS FAT STORAGE OVER LIPOLYSIS IN ADIPOSE TISSUE. OUR PRELIMINARY DATA SUGGEST THAT OLEIC ACID PROMOTES LIPID ACCUMULATION IN BOVINE FAT CELLS (ADIPOCYTES) AND INCREASES THE NUMBER OF MITOCHONDRIA IN PERIPARTURIENT COWS' ADIPOSE TISSUE. HOWEVER, THE SPECIFIC MECHANISMS UNDERLYING OLEIC ACID'S EFFECT ON CONTROLLING LIPID METABOLISM IS STILL UNKNOWN. THE OBJECTIVE OF THIS PROPOSAL IS TO DEFINE THE MECHANISM BY WHICH OLEIC ENHANCES LIPID ACCUMULATION AND IMPROVES MITOCHONDRIAL FUNCTION IN BOVINE ADIPOCYTES. WE WILL ALSO DETERMINE IF THIS MECHANISM REDUCES OXIDATIVE DAMAGE DURING LIPOLYSIS. THECENTRAL HYPOTHESISIS THAT OLEIC ACID REDUCES REACTIVE OXYGEN SPECIES PRODUCTION BY ENHANCING LIPID ACCUMULATION, COUNTERACTING LIPOLYSIS, AND IMPROVING MITOCHONDRIAL FUNCTION THROUGH PLIN5 PROTEIN. WE WILL DEVELOP THE HYPOTHESIS IN TWO AIMS. AIM 1 WILL DEFINE THE MECHANISM BY WHICH OLEIC ACID LIMITS LIPOLYSIS AND ENHANCES LIPID ACCUMULATION IN BOVINE ADIPOCYTES. AIM 2 WILL DETERMINE THE EFFECT OF OLEIC ACID ON MITOCHONDRIAL FUNCTION AND REACTIVE OXYGEN SPECIES PRODUCTION IN BOVINE ADIPOCYTES DURING LIPOLYSIS. UPON COMPLETION OF THIS PROJECT, WE WILL BE ABLE TO DETERMINE THE ROLE OF OLEIC ACID IN LIMITING EXCESSIVE LIPOLYSIS AND ADIPOSE TISSUE DYSFUNCTION. THIS WORK WILL ENRICH OUR CURRENT KNOWLEDGE IN DAIRY CATTLE LIPID METABOLISM AND ON FARM APPLICATION TO IMPROVE OVERALL COW HEALTH AND PRODUCTION.