Tannic acid as a multi-target regulator of intestinal barrier function in livestock

The intestinal barrier serves as a critical defense system that prevents pathogen invasion and the translocation of toxins. A compromised barrier initiates a cascade of damage, including impaired mucus secretion, dysregulated inflammatory responses, reduced antioxidant capacity, and microbial dysbiosis. Emerging evidence has highlighted polyphenolic phytochemicals as promising candidates for restoring the barrier. Tannic acid (TA), a hydrolysable tannin, demonstrates multi-mechanistic potential to restore intestinal barrier integrity. This potential originates from its distinctive chemical structure, which functionally ensures the performance of these multiple biological roles. This review synthesizes current evidence on the mechanisms by which TA reinforces intestinal barrier function. Tannic acid remodels the gut microbiota to increase the production of beneficial metabolites, such as butyrate, which subsequently strengthens the physical barrier by upregulating tight junction proteins. In parallel, TA directly enhances the antioxidant defense via the Nrf2 pathway and modulates intestinal immune response by suppressing key pro-inflammatory signaling pathways, including NF-κB and NLRP3. However, the practical application of TA is limited by anti-nutritional effects, necessitating the development of mitigation strategies, such as microencapsulation or synergistic formulations. Overall, this review aims to provide insights into the potential applications of TA for the prevention and treatment of intestinal disorders in livestock and poultry.