Liquid-fermentation-derived Candida utilis protein improves nutrient digestibility and intestinal health in weaned piglets

Objective This study aims to elucidate the nutritional functions and practical application value of Candida utilis single-cell protein derived from corn steep liquor in piglet diets. Methods In this study, 90 weaned piglets (initial body weight: 7.24 ± 1.30 kg) were randomly assigned to 3 dietary treatments for 28 days, with soybean meal partially replaced by 0, 3%, or 5% corn steep liquor-derived Candida utilis single-cell protein (FP50) in diets formulated on an iso-nitrogenous and iso-energetic basis. Results Dietary inclusion of FP50 did not impair growth performance, feed efficiency, or diarrhea incidence. In contrast, apparent total tract digestibility of DM and CP increased with increasing FP50 inclusion ( p < 0.01). Intestinal status was improved, as evidenced by reduced jejunal CD ( p < 0.05), increased V/C ratio ( p < 0.05), and decreased concentrations of BCFAs in the cecum ( p < 0.05). Moreover, FP50 supplementation modulated the cecal microbiota by enriching specific genera (e.g., Blautia , Romboutsia , and Anaerobutyricum ), which Spearman correlation analysis revealed were positively associated with nutrient digestibility and intestinal morphology, but negatively associated with cecal BCFAs. Additionally, FP50 enhanced systemic antioxidant capacity, as reflected by increased serum SOD activity ( p < 0.05). Conclusion FP50 can partially replace soybean meal in weaned piglet diets without compromising growth performance, while improving nutrient utilization and intestinal health. Among the tested levels, 5% substitution exhibited the most consistent improvements, indicating that low-level FP50 inclusion may represent a feasible strategy for reducing soybean meal use in weaned piglet diets.