The objective was to determine the effects of supplementing a high-fiber (HF) diet with a multicarbohydrase enzyme (MC; 4000 units/g xylanase, 1000 units/g α-amylase, 500 units/g protease, 150 units/g β-glucanase) on net portal fluxes of glucose and lactate, insulin production and oxygen consumption by the portal-drained viscera (PDV) and whole animal (WAOC) in growing pigs. Three isocaloric/nitrogenous diets based on corn and soybean meal (SBM) with either 0% (CTRL) or 30% distillers dried grains with solubles (DDGS; 1:1 corn and wheat mixture; HF) were used; the third diet was supplemented with MC in addition to the 30% DDGS (HF+MC). Five 22.8 ± 1.6 kg gilts fitted with permanent catheters in the portal vein, ileal vein (to infuse para-amino hippuric acid to measure blood flow rate) and carotid artery were fed the 3 diets at 4% BW once daily at 0900 h for 7 d in a replicated 3 × 3 Latin square design. On d 7, pigs were placed in an open-circuit indirect calorimeter to measure WAOC and sample blood for 7 h postprandial. Net glucose and insulin production were calculated from portal-arterial differences × flow and PDV O₂ consumption was calculated as arterial-portal O₂ differences × flow. Diet had no effect (P > 0.10) on postprandial WAOC, flow rate, and lactate flux. Also, diet had no effect (P > 0.10) on overall postprandial PDV O₂ consumption, but altered (P < 0.05) postprandial PDV O₂ consumption from 240 to 360 min postprandial. Pigs fed CTRL had higher (P < 0.05) portal insulin and glucose fluxes, from 90 to 300 min, and net glucose flux from 90 to 240 min postprandial. However, pigs fed CTRL and HF+MC had similar (P > 0.10) postprandial net glucose flux, which was higher (P < 0.05) than pigs fed HF. Therefore, it was concluded that adding MC to the HF diet improved net glucose portal flux in pigs.