This experiment was conducted to examine the influence of varying levels of fibrolytic enzyme on oat grass silage nutrient digestibility and ruminal characteristic in ruminally cannulated buffalo bulls using 4 × 4 Latin square design. The enzyme used was blend of xylanase (350000 BXU/g, where 1 BXU is the amount of enzyme that will release 0.06 micromole of reducing sugar (xylose equivalent) from birch xylan per minute at pH 5.3 and 50°C) and cellulase (10000 ECU/g, where 1 ECU is the amount of enzyme that will release 0.06 micromole of reducing sugars as glucose from hydroxethyl cellulose per minute at pH 4.8 and 50°C) and was derived from Trichoderma reesei. The control diet (C) was without enzyme, whereas diets containing 1, 2 and 3 g enzyme per Kg of silage’s dietary neutral detergent fiber (NDF) were denoted as low (LE), medium (ME) and high enzyme (HE) diets, respectively. Animals were fed only silage twice daily at 1% of their body weight. The apparent silage DM digestibility by animals fed ME diet (63.4 ± 3.70) was significantly higher (P < 0.05) and was lowest in animals fed C diet (60.7 ± 3.11). Similar trend was noticed in CP, NDF and ADF digestibility. The ruminal pH was higher (P < 0.05) in animals fed LE (6.73 ± 0.05), ME (6.64 ± 0.04) and HE (6.65 ± 0.06) diets than those fed C diet (6.52 ± 0.04). Similarly, ruminal NH₃-N concentration (mg/dL) was higher (P < 0.05) in animals fed LE (20.4 ± 2.05), ME (20.6 ± 2.21), HE (21.1 ± 1.96) diets than those fed C diet (18.7 ± 1.91). The blood glucose was higher (P < 0.05) in animals fed LE, ME and HE diets than those fed C diet at 3 and 6 h postprandial. However, blood urea nitrogen remained unaltered across all diets. In conclusion, enzyme supplementation increased nutrient digestibility, ruminal NH₃ and blood glucose.