Characterization of dry- and fresh-period mammary plasma flow and metabolism and their association with colostrum production in multiparous Holstein cattle

began to steadily increase starting at wk-2, while mammary acetate and glc uptake only began to increase at wk-1 and d-4, respectively. The earlier increase in mammary acetate uptake may suggest its role in providing energy for mammogenesis and lactogenesis I, while mammary glc uptake may coincide with lactogenesis II and copious milk production. Assuming the complete oxidation of mammary acetate and glc uptakes, the average daily rate of energy expenditure of the dry mammary gland was 0.93 Mcal/d and equated to a total energy expenditure of 56.1 Mcal throughout the entire dry period. Correlation and regression analyses highlighted the importance of achieving adequate dry-off during the far-off period of high-producing cows in promoting colostrum production, as greater previous lactation milk yield and far-off mammary acetate uptake were negatively associated with colostrum yield. In summary, the mammary gland appears to achieve a non-secretory, low metabolic state between wk-6 to wk-4 relative to calving, and this period appears to be of greater importance in driving colostrum production than the close-up period. Future work should aim to uncover the relationships between dry period mammary metabolism, especially the non-secretory state during the far-off period, and prepartum mammogenesis and colostrogenesis.