Bacillus subtilis has been widely investigated as a probiotic feed additive for weanling piglets due to its potential to improve growth performance, gut health, and disease resilience during the post-weaning period. This systematic review evaluated the effects of Bacillus subtilis supplementation in pigs following PRISMA guidelines and the PICOS framework. A total of 619 records published between 2000 and 2025 were identified through PubMed, Scopus, and AGRICOLA databases, of which 29 studies met the inclusion criteria for qualitative synthesis. Overall, Bacillus subtilis supplementation frequently improved average daily gain, body weight, feed efficiency, and reduced diarrhea incidence, particularly under enteric challenge conditions. Many studies also reported beneficial effects on intestinal morphology, immune regulation, intestinal barrier-related gene expression, nutrient digestibility, and modulation of gut microbiota toward bacterial communities associated with intestinal health. However, responses varied depending on Bacillus subtilis strain, dosage, diet composition, and experimental design. In contrast, effects on biochemical and oxidative stress indicators were less consistent across studies. Collectively, the findings support the potential role of Bacillus subtilis as a functional probiotic in swine nutrition while highlighting the need for standardized long-term studies to better define optimal strains, supplementation strategies, and mechanisms of action.
Ludorf et al. (Fri,) studied this question.