Fermented bread, a promising additive to pig feed to improve intestinal health—an <i>in vitro</i> study

Background Weaning stress in piglets leads to digestive disorders and compromised intestinal barrier function. Dietary fibres and bioactive compounds like volatile fatty acids represent promising alternatives to antibiotics. This study investigated the potential of fermented bread as a sustainable feed additive to improve intestinal health in pigs through in vitro digestion and cell culture models. Methods White bread (WB) and wholemeal bread (MB) were fermented anaerobically for 8 days at 35 °C. Bread samples and their fermented products (fermented white bread (FWB) and fermented wholemeal bread (FMB)) were analysed for their nutritional composition (protein, dietary fibres and volatile fatty acids), subjected to in vitro oro-gastrointestinal digestion using the INFOGEST protocol, and tested on porcine jejunal epithelial cells (IPEC-J2) for barrier function assessment. The cell viability and integrity of the IPEC-J2 were analysed by transepithelial electrical resistance, MTS assay, and immunohistochemistry for tight junction proteins (zonula occludens-1, ZO-1). Additionally, monitoring of the diffusion of FITC-dextran (FD4) and lucifer yellow (LY) through the cell monolayer was performed. Results Overall, fermentation significantly altered the nutritional profile of the breads, increasing the volatile fatty acids content, particularly lactic and butyric acid ( e.g. ; in FMB 29.8 and 10.6 mg/g of total dry mass, respectively). In vitro digestion showed 93% mass loss when enzymes were present, indicating high digestibility. Cell culture experiments revealed that, when exposed to the digesta, the IPEC-J2 maintained their viability (&gt; 90%) and barrier function, with only MB showing significant increases in LY permeability ( P &lt; 0.05). Fermented bread represents a promising sustainable feed additive that maintains intestinal barrier integrity while providing beneficial volatile fatty acids, particularly lactic acid and butyric acid, suggesting its potential as an antibiotic alternative in pig nutrition.