## 4 Discussion  
Soybean meal is widely used in the pig industry as a significant plant-based protein source due to its high amino acid content and cost-effectiveness [19]. Although it contains high protein, vitamins, and minerals, it has been rarely used directly because of its highly unacceptable characteristics such as its high satiety value, poor digestibility, the presence of anti-nutrients (e.g., trypsin inhibitors, hemagglutinin, and antivitamins), bitterness, and long cooking time [20; 21; 22]. Microbial fermentation can be employed to remove anti-nutritional compounds, undigested elements, and certain large molecular nutrients from soybean meal. Previous studies have shown that the fermentation process involving _B. subtilis_ ZJ12-1 can effectively degrade \(\beta\)-conglycinin and glycinin, the major antigenic proteins present in soybeans. This process results in the production of smaller peptides with antioxidant properties. [23]. Furthermore, the fermented soybean meal in the feeds can introduce additional probiotics and their metabolic by-products, including vitamins, exoenzymes, and various short-chain fatty acids. This can lead to improved digestive, absorptive,  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Items**} & \multicolumn{4}{c}{**VBP, g/kg**} & \multirow{2}{*}{**SEM**} & \multicolumn{2}{c}{**_p_-Value**} \\ \cline{2-2} \cline{5-8}  & **0** & **10** & **20** & **30** & **Linear** & **Quadratic** \\ \hline \hline \multirow{4}{*}{
\begin{tabular}{c} Backfat thickness, mm \\ LMP, \% \\ \end{tabular} } & \multicolumn{4}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\  & 63.61 & 63.70 & 63.79 & 63.79 & 0.326 & 0.685 & 0.897 \\ \cline{1-1}  & & \multicolumn{4}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\  & 12.26 & 12.40 & 12.54 & 12.49 & 0.210 & 0.386 & 0.638 \\ \cline{1-1}  & 61.49 & 61.49 & 61.39 & 61.70 & 0.255 & 0.638 & 0.544 \\ \cline{1-1}  & & \multicolumn{4}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\  & 17.51 & 17.46 & 17.31 & 16.94 & 0.205 & 0.054 & 0.451 \\ \cline{1-1}  & 57.49  & 57.97  & 58.27  & 58.16  & 0.200 & 0.016 & 0.147 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Effect of dietary vitamin B\({}_{2}\) from fermented soybean VBP supplementation on backfat thickness and lean meat percentage in growing-finishing pigs 1.  
and immune functions in pigs [24; 25]. Consequently, a range of processing methods, including heat treatment, enzymatic processes, and fermentation, have been employed to deactivate undesirable components in order to enhance the nutritional quality of soybeans for swine [19; 26; 27]. Fermentation is a suggested method for improving the flavor, texture, and nutritional value of feedstuffs and/or agro-industrial by-products [23; 28; 29]. Various _Bacillus_ species have been substantially used as host strains for the industrial processing of vitamins, proteases, purine nucleotides, etc. [30; 31; 32]. The VBP used in the present study is a residue collected after the extraction of vitamin B\({}_{2}\) from fermented soybeans. In this study, we substituted a portion of corn and soybean meal with VBP and investigated the impact of different levels of VBP supplementation on growth performance, blood parameters, nutrient utilization, and meat quality.