The objective was to evaluate if synergistic effects exist between an exogenous fibrolytic enzyme mixture (EFE) and a recombinant bacterial expansin-like protein (BsEXLX1) on ruminal in vitro neutral detergent fiber digestibility (NDFD) and preingestive hydrolysis of bermudagrass silage. In Experiment 1 (E-1), the effects of 2 levels of EFE (0, 2.33 mg/ g) and 4 levels of BsEXLX1 (0, 136, 272, 408 µg/ g) were tested on bermudagrass silage in a 4 × 2 factorial arrangement of treatments. Samples were preincubated with EFE and BsEXLX1 using sodium phosphate buffer (pH 6) for 1 h at room temperature in triplicate and further incubated in rumen fluid media for 24 h at 39°C. The experiment was repeated 3 times. In Experiment 2 (E-2), synergistic effects of the same levels of EFE and BsEXLX1 on preingestive hydrolysis were examined in quadruplicate by incubating ground bermudagrass silage samples (0.5 g) for 24 h at 25°C and measuring DM loss and NDF hydrolysis. Data were analyzed using the NMLE package of R and the model for E-1 included the fixed effects of EFE, BsEXLX1, run, interactions and the random effect of cow nested within run. The model for E-2 included the fixed effects EFE, BsEXLX1, run, and interactions. In E-1, DMD and NDFD were increased by 7% (46.9 vs 50.3%, P < 0.01) and 3% (35.4 vs 36.4%, P < 0.01) by EFE, respectively. However, no interactions or synergistic effects on DMD (49.6, 50.4, 50.6, and 50.4%, P = 0.8) and NDFD (36.0, 36.8, 36.6 and 36.0%, P = 0.2) were observed when BsEXLX1 was added with EFE. Total VFA was increased by 9% with EFE compared with control (83.7 vs 91.1 mM, P < 0.01) and reduced by 5% (87.4 vs 92.3, 86.7 and 83.3 mM, P < 0.01) by the highest dose of BsEXLX. In E-2, compared with the Control, EFE increased DM loss and NDF loss by 25% (21.4 vs 26.9%, P < 0.01) and 15% (20.9 vs 24.1%, P < 0.01), respectively but the expansin had no effect. In conclusion, the EFE increased DM and NDF digestibility of bermudagrass silage but the BsEXLX1 did not. The BsEXLX1 dose did not affect DM loss and NDF hydrolysis. The efficacy of the EFE was not improved when various doses of BsEXLX1 were added.