** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** ACHIEVING MAXIMAL GROWTH, DEVELOPMENT, AND PRODUCTIVITY IN THE DAIRY COW'S UDDER DEPENDS ON THE UNRESTRICTED DELIVERY OF NUTRIENTS FROM THE BLOOD. WHILE IT IS WELL APPRECIATED THAT BLOOD VESSELS DELIVER THE NUTRIENTS TO THE MILK SYNTHESIZING TISSUES IN THE COW'S UDDER AND REMOVE METABOLIC WASTE PRODUCTS, IT IS UNKNOWN HOW AND WHEN BLOOD VESSELS GROW AND DEVELOP WITHIN THE COW'S UDDER DURING KEY DEVELOPMENTAL TIME POINTS AND LACTATION. THE OVERARCHING HYPOTHESIS BEING TESTED HERE IS THAT THE MILK SYNTHESIZING TISSUES OF THE COW'S UDDER DIRECTS BLOOD VESSEL GROWTH AND FUNCTION. THE FIRST RESEARCH OBJECTIVE IS TO IDENTIFY THE MECHANISMS THAT DRIVE BLOOD VESSEL GROWTH DURING FIRST PREGNANCY, WHICH IS WHEN THE UDDER'S SECRETORY TISSUE IS RAPIDLY GROW AND DEVELOP IN PREPARATION FOR LACTATION. THE SECOND OBJECTIVE IS TO DETERMINE IF BLOOD VESSEL GROWTH CONTINUES INTO EARLY LACTATION AND IDENTIFY THE MECHANISMS THAT REGULATE BLOOD VESSEL FUNCTION AND SUBSTRATE EXCHANGE. WE EXPECT THAT BLOOD VESSEL GROWTH WILL CONTINUE INTO EARLY LACTATION, AS MILK PRODUCTION INCREASES, AND THAT BLOOD VESSEL GROWTH AND FUNCTION WILL BE SIGNIFICANTLY ASSOCIATED AND INFLUENCED BY THE PRODUCTIVITY OF THE COW'S UDDER. THE SIGNIFICANCE OF THIS RESEARCH IS THAT WE WILL DETERMINE WHEN AND HOW BLOOD VESSELS GROW AND INCREASE THEIR FUNCTIONALITY TO ALLOW THE MILK SECRETING TISSUE TO REACH IT'S MAXIMAL POTENTIAL. ALLOWING THE UDDER TO BE FULLY DEVELOPED AND UNHINDERED INCREASE MILK PRODUCTION EFFICIENCY WHICH IMPROVES DAIRY PRODUCTION SUSTAINABILITY AND PRODUCER PROFITABILITY.