In a feeding trial with four captive giraffes, nutrient digestibility was determined using four different marker systems. Although cobalt-ethylenediaminetetraacetic acid proved to have no utility as a digestibility marker in this study, reasonable values could be obtained using C36 n-alkane, acid detergent lignin, and acid insoluble ash as markers. A comparison of methods and literature data suggests that the values derived from the C36 n-alkane assay are the most reliable absolute values. Apparent digestibility ranges thus determined were 63.5-74.3% for dry matter, 73.4-82.4% for crude protein, 49.9-62.2% for neutral detergent fiber, and 49.7-63.7% for acid detergent fiber. However, digestibility data gained by the ADL method provided the most stringent inter-individual comparisons. It is concluded that both alkanes and lignin can be used for giraffe digestibility studies. These captive giraffes ingested a smaller quantity of food than has been reported for other giraffes from both the wild and other zoos. Energetic calculations showed that these animals might be on the brink of an energy deficit. A similar situation has been described at least once before in captive giraffes, and the results are of direct relevance to the peracute mortality syndrome, a condition of captive giraffes in which severe depletion of body fat stores occurs. Reasons for the seemingly low food intake could not be elucidated, but observations suggested that these giraffes were ready to ingest more if more palatable or suitable food was offered. Monitoring food intake in other giraffe groups and designing a diet that is both palatable and nutritious are important objectives of captive giraffe management.