The objective of this study was to investigate the effect of Pansengold (1.58 mol of calcium propionate, 65 mmol of glycerol, 1.3 mu mol of riboflavin) on rumen flora and fauna and on calcium and energy balance in dairy cows. Twenty cows each were administered after calving with Pansengold via stomach tube (cases) or left untreated (controls). Before administration as well as 1, 3, 6, and 24 hours later rumen and blood samples were taken. Rumen samples were used for methylene blue test; the numbers of mobile (active) or immobile (inactive) rumen protozoa were counted and the percentage of active protozoa was calculated; ruminal pH was measured. Blood samples were used to determine total calcium and beta-hydroxybutyrate (BHB). Pansengold significantly speeded up methylene blue test 3-24 hours after administration, increased the number of active protozoa 3-24 h p. a., lowered the number of inactive protozoa 1-24 h p. a., increased the percentage of active protozoa 1-24 h p. a., and lowerd ruminal pH 1-24 h compared to untreated controls. Pansengold significantly increased blood total calcium 3-6 h p. a., and lowered blood BHB 1-6 h p. a. compared to untreated controls. Pansengold proofed effective to activate rumen flora and fauna and to supply calcium and energy in dairy cows.