Encapsulation complex of essential oils, organic acids, and antioxidants improves growth performance and intestinal health in Escherichia coli-challenged weaned pigs

This study investigated the effects of dietary supplementation with a coated complex of essential oils, organic acids, vitamin E, and selenium on growth performance, intestinal health, immune responses, and gut microbiota in Escherichia coli-challenged weaned pigs. Twenty-four crossbred (Landrace × Yorkshire × Duroc) weaned pigs (12 barrows and 12 gilts; 4 weeks of age; initial body weight 9.61 ± 0.81 kg) were randomly assigned to four treatments in a completely randomized design, with six replicates per treatment and one pig per pen, for 14 days experimental period. The dietary treatments were as follows: non-challenged control (PC), challenged control (NC), NC with 0.05% additive (T1), and NC with 0.10% additive (T2). Pigs in NC, T1, and T2 were orally challenged with <italic>E. coli</italic> K88 on days -2 to 0. On day 7, body weight was significantly higher in T1 and T2 than NC (p < 0.05), and average daily gain was greater in T1 than NC during days 0–7 (p < 0.05). Fecal scores were significantly lower in PC, T1, and T2 than NC during weeks 1 and 2 (p < 0.05). Apparent total tract digestibility of dry matter, crude protein, and gross energy did not differ among treatments (p > 0.05). Ileal villus height to crypt depth ratio was significantly higher in PC, T1, and T2 than NC (p < 0.05). Expression of claudin-1 and mucin-1 was significantly higher in T1 and T2 than NC and PC (p < 0.05), while zonula occludens-1 expression was higher in T1 than NC (p < 0.05). On day 3 post-challenge, serum interferon-γ was significantly higher in T1 and T2 than PC (p < 0.05), and interleukin-8 was elevated in T2 compared to PC (p < 0.05). Beta diversity analysis revealed significant differences in microbial community structure between treatments. At the genus level, T2 showed significantly higher relative abundances of Lactobacillus and Megasphaera than other groups (p < 0.05). In conclusion, dietary supplementation with this coated complex at 0.05% and 0.10% improved growth performance, intestinal morphology, barrier function, and immune responses in <italic>E. coli</italic>-challenged weaned pigs.<strong> </strong>