This presentation will update our understanding of the role in dietary cation anion difference (DCAD) in dairy cattle nutrition during both the prepartum and postpartum periods. During the prepartum period, decreasing the DCAD improves calcium metabolism and decreases hypocalcemia as evidenced by a number of studies and recent meta analyses. During the postpartum period, increasing the dietary DCAD appears to improve milk and milk component yield; however, in many cases it may be difficult to separate the effect of DCAD with increased ruminal buffering capacity based upon the supplements used to increase the dietary DCAD.