Energy consumption and subsequent partitioning in lactating black-tailed deer

The voluntary feed intake of lactating Odocoileus hemionus columbianus does was measured to 4 months after parturition. Similar measures of consumption by nonlactating does showed average dry matter intakes of 67 g∙kg −0.75 ∙day −1 (247 kcal digestible energy∙kg −0.75 ∙day −1 ; 1 cal = 4.1868 J). At peak consumption rates, 4–5 weeks after parturition, lactating does with twin fawns consumed 170% of the intake of nonlactating does. For does with single fawns the rate was 135%. Body weight changes in early lactation varied between does, with some individuals utilizing body reserves to maintain milk production whereas others remained in a positive caloric balance. For the rest of lactation, voluntary feed intakes were sufficiently high to allow all does to both produce milk and increase in body weight.