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.

Ophiopogon japonicus (O. japonicus) by-products contain abundant nutrients and bioactive substances. In this study, we evaluated their effects on production performance and intestinal health in meat rabbits. Firstly, we measured the nutrient levels of O. japonicus by-products along with its digestibility in meat rabbits. Then, we replaced dietary alfalfa meal with O. japonicus by-products to evaluate its effects on growth performance, carcass traits, apparent digestibility, and intestinal immunity in meat rabbits. The results showed that the effects of O. japonicus by-products on growing meat rabbits varied over time. In the early phase (days 1–21), it significantly depressed average daily gain (ADG, p < 0.001) and average daily feed intake (ADFI, p < 0.001), and increased feed to gain ratio (F:G) (p < 0.001). However, in the later phase (days 22–35), a compensatory response emerged, with significantly increased ADG (p < 0.001) and reduced ADFI (p < 0.01) and F:G (p < 0.001). Despite this compensatory growth, the growth performance and feed efficiency for the entire experimental period were not improved. O. japonicus by-products decreased carcass weight significantly (p < 0.001), but did not significantly affect dressing percentage and meat traits (p > 0.05), while it significantly reduced the digestibility of crude protein (CP, p < 0.05), increased that of crude fiber (CF, p < 0.001), and reduced the activities of amylase (p < 0.01) and increased trypsin in cecal contents (p < 0.05). Additionally, O. japonicus by-products elevated the levels of secretory immunoglobulin A (sIgA) and interleukin-10 (IL-10) in ileal mucosa (p < 0.05). They did not significantly affect the cecal microbial community or short chain fatty acid (SCFA) levels (p > 0.05). Our research indicated that O. japonicus by-products possess a balanced nutritional composition and improve intestinal immunity in rabbit production, making them a viable feed ingredient to partially replace alfalfa meal.

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 (p_adj < 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 (p_adj < 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.