Lack of potassium-anion interaction in diet selection by captive meadow voles

An experiment was conducted to test whether selective avoidance of high-potassium diets by captive meadow voles (Rodentia: Microtus pennsylvanicus) depends on the anions with which potassium is associated. Voles were presented simultaneously with a) low- and high-potassium diets formulated with either potassium sulfate, potassium chloride, or a mixture of potassium chloride and potassium citrate; or b) paired combinations of high-potassium diets containing different anions. In the first part of the experiment, voles preferentially selected the low-potassium diets, with the degree of selectivity virtually completely independent of the associated anion. These results confirm previous suggestions that potassium avoidance may be a component in diet selection by herbivores, especially during spring and summer. There is only weak indication that anion content affects selection of diets with fixed potassium content.