Extrusion and Extrusion Combined with Solid-State Enzymatic Hydrolysis Improve the Nutrient Digestion of Rapeseed Meal in Growing Pigs

Rapeseed meal (RSM) is an important protein source in animal feed, but its high levels of anti-nutritional factors and crude fiber (CF) limit its utilization in pigs. Our study compared the morphological structure, nutrient composition, and anti-nutritional factors of RSM, extruded rapeseed meal (ERM), and extruded solid-state enzymatically hydrolyzed rapeseed meal (EERM), and evaluated their digestibility in growing pigs. The results showed that ERM and EERM increased surface porosity. Notably, ERM and EERM had higher trichloroacetic acid-soluble protein contents and lower fiber, glucosinolate (GL), and isothiocyanate (ITC) contents. Compared to RSM, the in vitro digestibility of crude protein (CP) was significantly lower in ERM (p < 0.05), whereas EERM exhibited significantly higher digestibility of CP than ERM (p < 0.05). Additionally, compared to RSM and ERM, the digestibility of dry matter (DM) and gross energy (GE) increased significantly in EERM (p < 0.05). For in vivo digestibility, compared to ERM, the digestibility of CP and GE increased significantly in EERM (p < 0.05). In conclusion, our study demonstrates that ERM and EERM can change the chemical composition of RSM, and improve the digestibility of nutrients in pig production.