Effects of a blend of essential oils and an enzyme combination on nutrient digestibility, ileum histology and expression of inflammatory mediators in weaned piglets

The aim of this study was to test the hypothesis of an improved gut environment of post-weaning piglets when administered a blend of essential oils (EO; thymol and cinnamaldehyde) and an enzyme combination (xylanase and β-glucanase (XB)) either alone or in combination. To assess the effect of dietary treatments, faecal nutrient digestibility and microbial counts, as well as ileum histology and gene expression of inflammatory mediators were evaluated. One hundred and ninety-two weaned piglets were allocated into four experimental treatments, and fed the basal diet (CTRL) either without or with EO, XB or their combination (EO+XB) for a 42-day period. The experiment concerning digestibility was designed with two periods (period I: days 15 to 21; period II: days 29 to 35) and the faeces were collected on days 20, 21, 34 and 35. On day 42, six piglets from each treatment were slaughtered. It was found that EO, XB and EO+XB supplementation did not affect (P>0.05) the growth performance of the piglets from days 0 to 42. Moreover, no dietary effect on faecal score was observed. Faecal digestibility of dry matter, organic matter, ash, dietary fibre, lipid, CP and NDF were increased from period I to period II (P<0.01 to P=0.06), while no effect (P>0.05) of EO, XB or their combination on the faecal digestibility was observed at both periods. Compared with the CTRL diet, dietary XB reduced the faecal Lactobacillus and Escherichia coli counts but increased the Lactobacillus to Coliforms ratio on day 42 (P=0.02, 0.03 and 0.03, respectively), and all the additives supplementations decreased the counts of faecal Coliforms on day 42 (P<0.01). XB supplementation increased the villus to crypt ratio (P=0.04) and reduced the mucosal macrophages number (P<0.01) in the ileum compared with the CTRL group, and dietary EO or EO+XB decreased the number of lymphatic follicles (P=0.01 and P<0.01, respectively) and mucosal macrophages (P=0.02 and P<0.01, respectively). In addition, the interleukin (IL)-1α was downregulated in piglets treated with EO+XB compared with the EO group (P=0.02). In conclusion, the administration of EO, XB or their combination was effective in improving ileum histology, and EO+XB upplementation might benefit the modulation of the expression of ileum inflammatory cytokines in piglets.