Extrusion Combined with Fermentation Modifies Chemical Composition and Methionine Availability in Rapeseed Meal for Growing Pigs

Rapeseed meal (RSM) is a promising protein ingredient for animal feed; however, its utilization is limited by poor digestibility and the presence of anti-nutritional factors. In this study, we first investigated the effects of extrusion and fermentation on the structural characteristics and chemical composition of RSM. Subsequently, 18 growing pigs (6 pigs per treatment, 1 pig per replicate) were used. In period 1, pigs received diets with 20% RSM or fermented extruded rapeseed meal (FERSM) for nutrient digestibility determination. After a 7-day washout, the same pigs were re-assigned to 30% RSM or FERSM diets (6 pigs per treatment) for amino acid digestibility measurement. The results showed that extrusion combined with fermentation resulted in a more porous and loosened structure of RSM. Compared with RSM, FERSM exhibited a significant reduction in glucosinolate (GLs) content, whereas trichloroacetic acid-soluble protein (TCA-SP) content was significantly increased (padj < 0.001). Furthermore, pigs fed the FERSM diet showed significantly higher standardized ileal digestibility (SID) and standardized ileal digestible content of methionine (Met) than those fed the RSM diet (padj < 0.05). In conclusion, extrusion combined with fermentation, when wheat bran was included in the substrate, effectively modified the physicochemical properties and chemical composition of RSM and was associated with improved Met utilization in growing pigs.