The aim of current study was to investigate whether degradation of rapeseed meal (RSM) by a swine gut microbiota consortium was improved by modifying RSM by treatment with cellulase (CELL), two pectinases (PECT), or alkaline (ALK) compared to untreated RSM and to assess whether microbiota composition and activity changed. The predicted relative abundances of carbohydrate digestion and absorption, glycolysis, pentose phosphate pathway, and pyruvate metabolism were significantly increased upon CELL and ALK feeding, and CELL and ALK also exhibited increased total short-chain fatty acid (SCFA) production compared to CON. Megasphaera, Prevotella, and Desulfovibrio were significantly positively correlated with SCFA production. Findings were validated in ileal cannulated pigs, which showed that CELL and ALK increased fibre degradation of RSM. In conclusion, CELL and ALK rather than PECT1 or PECT2 increased fibre degradation in RSM, and this information could guide feed additive strategies to improve efficiency and productivity in the swine industry.