Narrative review of probiotics in monogastric animals shows enzyme increases and lipid peroxidation reductions.

Probiotics, defined as living microorganisms that confer health benefits when administered in adequate amounts, have demonstrated significant potential in enhancing productivity and physiological resilience in monogastric animals, including poultry, companion animals, and swine. This narrative review synthesizes recent evidence on the antioxidant, anti-inflammatory, antistress, and growth-promoting functions of commonly studied probiotic genera, such as Lactobacillus, Bifidobacterium, Bacillus, and Saccharomyces. Probiotics improve physiological homeostasis through multiple mechanisms. As antioxidants, they enhance endogenous enzyme activities including catalase, superoxide dismutase, and glutathione peroxidase resulting in 15–40% increases in enzyme activity and 20–45% reductions in lipid peroxidation markers, indicating improved oxidative balance. Antistress effects are mediated via modulation of the gut–brain axis, lowered corticosterone levels, and immune regulation through cytokine changes (IL-6, TNF-α, IL-10). Additionally, probiotics support intestinal integrity, reduce pathogenic load, and enhance nutrient utilization, contributing to 5–12% improvements in feed efficiency under controlled conditions. The efficacy of probiotics depends on strain specificity, dosage, delivery method, and host factors, emphasizing the need for precise formulation. In conclusion, probiotics offer a promising nutritional strategy for improving health, stress tolerance, and productivity in monogastric species. Future research should focus on elucidating molecular mechanisms, including Nrf2 signalling and gut barrier regulation, optimizing dosing strategies and exploring synergistic combinations with prebiotics and phytogenic additives. Such targeted approaches can maximize the benefits of probiotics and support sustainable, precision-driven monogastric production systems.