Is there an optimal cation-anion difference for lactation diets?

Because of the increased use of the cation-anion difference (CAD) concept in dry cow nutrition, many dairy nutritionists have been asking whether or not CAD is important in lactation diets. Two common questions are: (1) should CAD be monitored in rations formulated for lactating dairy cows?; and, (2) what is the optimal CAD for high producing dairy cows? A project was initiated to answer these questions. We combined data from ten macromineral nutrition experiments and conducted a regression analysis. This data base contained a wide range (+5.8 to +61.2) of dietary CAD (defined as the meq of Na + K − Cl per 100 grams of diet DM). Regression models indicated that the optimal CAD for lactation rations was between +25 and +50. Dietary CAD should be routinely monitored in rations fed to high producing dairy cows, however, commercial diets with CAD values outside the optimal range are probably uncommon.