We performed preference trials with 3 adult captive giraffes and a group of 3 juveniles in which the animals could choose between a regular pelleted feed and a pelleted feed of the same composition with an addition of 3 % (original weight) tannic acid. One animal completely refused the new diet item, another animal and the juvenile group ate the new diet item in varying amounts, and one animal ingested increasing amounts of the tannic acid item until it had replaced the regular pellet in its diet nearly completely. However, after 8-16 days, the intake of the new diet item decreased again in those animals that accepted it. For the two adult animals which included the tannic acid containing feed in their diet, overall daily dry matter intake increased significantly by 0.9-1.2 kg. The new diet item had no discernable influence on apparent digestibility coefficients. Our results indicate that the outcome of preference trials depends to a great extent on individual preferences, and on the duration of the choice period. The increase in food intake may have been due to the inclusion of tannic acid, or may simply have been an effect of increased food variety.