Influence of a blend of essential oils and an enzyme combination on growth performance, microbial counts, ileum microscopic anatomy and the expression of inflammatory mediators in weaned piglets following an Escherichia coli infection

• Effects of essential oils and enzymes on challenged weaned piglets were evaluated.
• Essential oils and enzymes may improve gastrointestinal tract (GIT) environment.
• Combination of essential oils and enzymes may improve GIT environment.
• Combination of essential oils and enzymes may have a synergistic interaction.

This study evaluated the effects of nutritional supplementation with a blend of essential oils (EO, thymol and cinnamaldehyde) and an enzyme combination (XB, xylanase and β-glucanase), given alone or together, on growth performance, microbial counts, ileum microscopic anatomy and the expression of inflammatory mediators in weaned piglets challenged with Escherichia coli K88. One hundred and ninety-two weaned piglets were allocated to 8 treatments in a 35-day experiment with a 2 × 4 factorial design that compared 2 levels of oral E. coli challenge [sham (−) or infected (+)] under different dietary treatments [fed the basal diet (CTR) either with or without EO or XB individually or in combination (EOXB)]. Half of the piglets were orally challenged with E. coli O149:F4 (K88) on day 8 and 48 piglets (1 piglet/pen) were slaughtered on day 35. The E. coli challenge was found to decrease the average daily gain (ADG) and the gain to feed (G:F) ratio from days 7 to 14 (P < 0.01) and to increase the fecal score from 1 to 5 days post-inoculation (P < 0.01). EOXB supplementation decreased the fecal score compared to the challenged CTR animals during the first week post-challenge (P = 0.02). The E. coli challenge increased the populations of fecal Clostridia, E. coli and coliforms on day 9 (P < 0.01) and increased E. coli and coliforms counts on day 14 (P < 0.01 and P = 0.01, respectively). Dietary EO and EOXB reduced the fecal coliforms count compared to the CTR group on day 14 (P = 0.02 and P < 0.01, respectively). Furthermore, EOXB supplementation reduced the coliforms count (P < 0.01) and tended to decrease the E. coli count (P = 0.051) compared to the CTR group in the cecum digesta. Dietary EOXB also decreased the crypt depth and increased the villus-to-crypt ratio in piglets compared to the CTR group (P < 0.01). The E. coli challenge up-regulated the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1α, toll-like receptor (TLR)2 and TLR4 (P < 0.01, P = 0.01, P = 0.03, P = 0.01, respectively), and EOXB supplementation down-regulated the expression of TNF-α (P < 0.01) and IL-6 (P = 0.046) compared to the EO group. The results suggest that the combination of EO and XB supplementation may have beneficial effects on the modulation of fecal consistency, microbial counts and ileum microscopic anatomy in weaned piglets following E. coli infection.