The impact of combined thymol and rosmarinic acid on the intestinal microbiota and barrier function of the piglets challenged by Escherichia coli K88

It has been found that thymol (Thy) and rosmarinic acid (Ros-A) improve the growth performance of piglets and relieve intestinal inflammation in animals. The effects of Thy and Ros-A separately or in combination (Thy × Ros-A) on the intestinal function and health of piglets challenged with <i>Escherichia coli</i> K88 (<i>E. coli</i> K88) were investigated. A total of 30 piglets aged 21 d were assigned to 5 groups (<i>n</i> = 6). The control (Con) and K88 groups piglets received a basal diet, while the Thy, Ros-A, and Thy × Ros-A groups were fed a basal diet supplemented with 500 mg/kg Thy, 500 mg/kg Ros-A, and 250 mg/kg Thy + 250 mg/kg Ros-A, respectively. On the 19th and 20th day, piglets in the K88, Thy, Ros-A, and Thy × Ros-A groups were orally administered 10 mL of phosphate-buffered saline (PBS) containing approximately 1 × 10⁹ CFU/mL of <i>E. coli</i> K88, while the Con group received an equal volume of PBS. The results showed that the Thy × Ros-A treatment reduced the damage to ileal villi induced by the <i>E. coli</i> K88 challenge, leading to longer villi in the ileum (<i>P</i> < 0.05). Thy and Ros-A modulated the composition of the ileal microbiota. Compared to the K88 group, the Thy × Ros-A group had a higher abundance of <i>Lactobacillus</i> and <i>Romboutsia</i>, while <i>Escherichia-Shigella</i> and <i>Desulforvibrio</i> were lower (<i>P</i> < 0.05). Additionally, the Thy × Ros-A group showed elevated levels of gene and protein expressions for zonula occludens-1, occludin, and claudin-1 compared to the K88 group (<i>P</i> < 0.05). In conclusion, combining Thy and Ros-A reduced ileal damage and relieved the inflammation in weaned piglets challenged with <i>E. coli</i> K88 by regulating intestinal microflora and improving barrier function.