We compared energy intake of reproductive and nonreproductive female Brandt's voles (Microtus brandtii). Daily energy intake of pregnant voles was significantly higher than that of nonreproductive voles. Metabolizable energy intake increased after parturition and reached a maximum at the end of lactation (334.23 kJ/day), 323% of typical nonreproductive requirements. Moreover, pregnant females had significantly higher lipid mass than controls. During lactation lipid contents were lower than in controls. Over the course of lactation females decreased by 17.6% in body mass, suggesting that females have depleted their body reserve. Use of energy reserves and maximum metabolizable energy intake both were dependent on litter size. Our results indicate that Brandt's voles meet most of their energy demands for lactation by increasing food intake but also supplement that energy by using body reserves even before food intake is maximized.