Northeast Research and Demonstration Farm
Ration formulation for dairy cows just prior to parturition must control the dietary cation-anion difference (DCAD) if hypocalcemia and milk fever are to be avoided. One key to reducing hypocalcemia is to avoid incorporation of high-K forages into the ration. The excessive K content of these forages can cause metabolic alkalosis in the cow and subsequently hypocalcemia and milk fever. Alfalfa and other cool-season grasses are often used in dairy rations. Reducing K content of forages can be achieved by restricting K fertilization so that soils do not support luxury consumption. Since K is the major cation contributing to highDCAD diets, an obvious solution is to limit K fertilization of the forage crop to avoid luxury consumption of K. However, some forages may have reduced yield and increased winter kill if K concentrations are less than 2.0%, particularly alfalfa. Thus, producing alfalfa with less than 2% K may not be profitable, especially in northern regions. In addition to decreasing forage K, the producer can also increase the Cl content of the forages, and the resulting DCAD will be more favorable for the late-gestation cows.
Iowa State University
Horst, Ronald L.; Goff, Jesse; Thoreson, Dale R.; Moore, Kenneth J.; Brummer, E. Charles; Russell, James R.; and Pecinovsky, Kenneth T., "Development of Methodologies to Reduce the DCAD of Hay Forages for Transition Dairy Cows" (2006). Iowa State Research Farm Progress Reports. 1101.