Name one nutritional requirement that is unique to pregnant animals.

During pregnancy, animals have specific nutritional needs to support the developing fetus. Increased energy intake is essential for pregnant animals because their metabolic demands rise significantly as they provide nourishment to the growing offspring. This additional energy supports fetal growth and development, as well as prepares the mother's body for the demands of lactation after birth.

While fiber, protein, and calcium are also important for overall health and can be increased during pregnancy, the most critical aspect in terms of immediate energy needs is the increased caloric intake. This ensures that both the mother and her developing young receive the necessary energy to thrive, making it a unique requirement during gestation.