The Effects of the Dietary Inclusion of By-Products Obtained after the Extraction of Vitamin B2 from Fermented Soybean on the Performance and Meat Quality of Growing–Finishing Pigs

The by-products obtained after the extraction of vitamin B2 from fermented soybean (VBP), primarily consisting of soybean meal, soybean oil, vitamin B2, and Bacillus subtilis, may serve as a cost-effective and recycled resource in animal feed. This research aimed to assess the impact of VBP on the growth performance, nutrient utilization, blood parameters, and meat quality of pigs in the growing–finishing phase. In this 16-week feeding experiment, 140 pigs of mixed breed [Duroc × (Landrace × Yorkshire)] were used, with an initial average body weight of 26.05 ± 1.32 kg. The pigs were assigned randomly to one of four dietary groups, each consisting of five pigs, with two gilts and three barrows per pen, and a total of seven repetitions per treatment. The animals were fed different levels of by-products after vitamin B2 extraction (0, 10, 20, and 30 g/kg as the CON, VBP10, VBP20, and VBP30 dietary groups, respectively) in a three-phase feeding trial (wk. 0–4, 4–8, and 8–13). When higher levels of VBP were added as supplements, the outcomes indicated that there were no notable variations (p > 0.05) in growth performance and nutrient digestibility among the treatment groups throughout the trial. In phase II (4–8 weeks), the inclusion of VBP in the diets showed a reduction (p = 0.011; with linear and quadratic effects, p = 0.003) in serum norepinephrine concentration. The sensory evaluation of meat color was linearly improved (p = 0.043) in pigs fed with graded levels of VBP supplementation. The percentage of lean meat showed a significant improvement (p = 0.016) with the gradual levels of VBP supplementation. The addition of 30 g/kg (on an as-fed basis) of vitamin B2 by-products in the diet can simultaneously mitigate the negative impacts of acute stress without compromising growth performance and enhance the percentage of lean meat. These findings suggest that VBP could be a viable and economical alternative to corn and soybean meal and partially replace it in pig feed.