Abstract: Ninety Holstein yearling steers (467 kg) were used in a 116-d trial to evaluate the influence of maceration on the feeding value of rice straw. Treatments consisted of a steam-flaked corn-based diet containing 15% forage (DM basis) as sudangrass, rice straw or macerated rice straw. All forages were ground to pass through a 2.6 cm screen prior to incorporation into complete mixed diets. There were no treatment effects (P > 0.20) on dressing percentage. However, there was a forage by enzyme interaction (P < 0.10) on DMI and ADG. Enzyme supplementation increased (5%) DMI and ADG of cattle fed diets containing macerated rice straw. Enzyme supplementation did not affect (P > 0.20) dietary NE, thus the improvement in ADG with enzyme supplementation of the macerated rice straw supplemented diet was due to increased in DMI. Gain efficiency, and dietary NE were greater (5 and 4%, respectively; P < 0.05) for macerated rice straw than for ground rice straw supplemented diets. The estimated NEm and NEg values for ground rice straw were 0.72 and 0.22 Mcal/kg, respectively. The corresponding values for macerated rice straw were 1.45 and 0.86 Mcal/kg, respectively. Enzyme supplementation did not affect (P > 0.20) dietary NE. Six steers with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on digestion. There were no treatment interactions (P > 0.20). Ruminal digestion of organic matter was similar across treatments (60.9%, P = 0.35). Ruminal NDF digestion was greater (25%, P < 0.10) for sudangrass than for rice straw supplemented diets, averaging 54 and 44%, respectively. Likewise, ruminal ADF digestion was also greater (43%, P < 0.10) for sudangrass than for rice straw, averaging 30.6 and 21.4 %. respectively. Maceration of rice straw did not affect (P > 0.20) extent of ruminal fiber digestion. Maceration increased (8%, P < 0.05) ruminal degradation of feed N over that of ground rice straw. Enzyme supplementation did not enhance (P = 0.95) ruminal NDF digestion, but increased total tract digestion of DM (4%, P = 0.06), OM (4%, P = 0.06), and NDF (P = 0.12). Total tract digestion of DM (4%, P < 0.01), OM (3%, P < 0.05), and NDF (31%; P < 0.01) were greater for sudangrass than for rice straw supplemented treatments. Maceration did affect (P > 0.20) total tract digestion of OM and fiber. We conclude that enzyme supplementation works synergistically with maceration to enhance the feeding value of low quality forages such as rice straw. The beneficial effects of fibrolytic enzymes on ruminal digestion are expected to increase as ruminal retention time of the fibrous components of the diet decrease.