Fermented Rapeseed Meal Improves Growth Performance, Antioxidant Capacity, and Intestinal Morphology of Broilers by Enhancing Nutritional Value and Reducing Antinutritional Factors

This study evaluated changes in nutritional components and antinutritional factors in rapeseed meal before and after microbial fermentation. It further investigated the enhancements in its nutritional value and the growth-promoting effects of fermented rapeseed meal on broiler chickens. A total of 180 one-day-old male Arbor Acres (AA) broilers were randomly allocated into 3 treatment groups, with 6 replicates per group and 10 birds per replicate. The broilers were fed a basal diet (CON), a diet with 5% soybean meal (SBM) replaced by RSM (RSM-5), or a diet with 5% SBM replaced by FRSM (FRSM-5). The date of the experiment was 28 June 2025. The results showed that FRSM improves protein quality and reduces the levels of antinutritional factors, including glucosinolates (GSL), phytic acid (PA), and condensed tannins (CT), compared with unfermented RSM. Additionally, FRSM enhances antioxidant capacity in vitro, significantly enhancing the scavenging rates of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, hydroxyl radicals (•OH), and superoxide anion radicals (O₂•^-). In the broiler feeding trial, the FRSM-5 group had significantly higher average daily gain (ADG) during the periods of 22-42 d and 1-42 d (<i>p</i> < 0.05), along with a significantly lower feed to gain ratio (F/G) (<i>p</i> < 0.05), compared with the CON and RSM-5 groups. Compared to the CON group, the FRSM-5 group showed a significantly higher slaughter rate (SR), full eviscerated rate (FER), and breast muscle rate (BMR) (<i>p</i> < 0.05), whereas the RSM-5 group had significantly lower SR and FER (<i>p</i> < 0.05). The activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) in the serum and liver of the FRSM-5 group were significantly higher than those in the CON and RSM-5 groups (<i>p</i> < 0.05), and the serum immunoglobulin (IgA, IgG, and IgM) levels were significantly elevated (<i>p</i> < 0.05). Furthermore, compared with the CON and RSM-5 groups, the FRSM-5 group exhibited a significant increase in duodenal villus height (VH) (<i>p</i> < 0.05), a significant reduction in duodenal crypt depth (CD) (<i>p</i> < 0.05), and a consequent significant increase in the VH/CD (<i>p</i> < 0.05). In conclusion, microbial fermentation effectively enhances the nutritional value of RSM by improving its nutrient composition and reducing antinutritional factors. Replacing 5% SBM with FRSM in broiler diets significantly improves growth performance, enhances antioxidant capacity and immune function, and optimizes intestinal morphological structure, thereby replacing part of the soybean meal in broiler diets.