Voles were fed diets low in protein, fat, sodium, and calcium, the pellets being coated with a chemical additive: 0.5% gramine, 5% quercetin, or 5% tannic acid. Survivorship, changes in body mass and food intake, and variations in kidney and liver masses and histopathology were measured. All diets caused a reduction in body mass. Duration of treatment and sex were the most important factors affecting mass loss. Mineral deficiencies affected kidney structure more severely than other dietary factors, but addition of secondary metabolites and a longer period of treatment did not accentuate the trend. The capacity of voles for long-term survival on diets that are nutritionally deficient and with secondary metabolites added shows their great ability to use low-quality food.