ABSTRACT: Objective: Our objectives were to compare the effects of feeding eucalyptus bark or eucalyptus wood chips, both by-products from the pulp industry, on voluntary feed intake, animal performance, and physiological variables of heifers finished on high-concentrate diets. Materials and Methods: Forty-eight British-breed heifers (Angus, Hereford, and their crosses) that were 22 to 24 mo of age and had an initial BW of 355 ± 8 kg were used. Four heifers were allocated to each of the 12 pens (experimental units). The experiment was a randomized complete block design with 2 treatments and 6 replications each. The 2 different fiber sources (wood chips or bark) were included in the fattening diet in the same proportion (8.9% DM basis). The rest of the ingredients in the diet were the same. The final diet was offered 3 times per day, and heifers were fed for 84 d. Results and Discussion: Fiber source (wood chips vs. bark) did not affect ADG or G:F (P > 0.10). However, DMI (P