Broiler gut microbiota and expressions of gut barrier genes affected by cereal type and phytogenic inclusion.

The present study assessed the effects of cereal type and the inclusion level of a phytogenic feed additive (PFA) on broiler ileal and cecal gut microbiota composition, volatile fatty acids (VFA) and gene expression of toll like receptors (), tight junction proteins, mucin 2 () and secretory immunoglobulin A (). Depending on cereal type (i.e. maize or wheat) and PFA inclusion level (i.e. 0, 100 and 150 mg/kg diet), 450 one-day-old male broilers were allocated in 6 treatments according to a 2 × 3 factorial arrangement with 5 replicates of 15 broilers each, for 42 d. Significant interactions ( ≤ 0.05) between cereal type and PFA were shown for cecal digesta and cluster XIVa, ileal digesta propionic and branched VFA, ileal gene expression, as well as cecal digesta branched and other VFA molar ratios. Cereal type affected the cecal microbiota composition. In particular, wheat-fed broilers had higher levels of mucosa-associated (  = 0.007) and digesta (  < 0.001), as well as lower levels of total bacteria (  = 0.004) and clusters I, IV and XIVa (  ≤ 0.05), compared with maize-fed ones. In addition, cereal type gave differences in fermentation intensity (  = 0.021) and in certain individual VFA molar ratios. Wheat-fed broilers had higher ( ≤ 0.05) ileal zonula occluden 2 () and lower ileal and cecal and levels, compared with maize-fed broilers. On the other hand, PFA inclusion at 150 mg/kg had a stimulating effect on microbial fermentation at ileum and a retarding effect in ceca with additional variable VFA molar patterns. In addition, PFA inclusion at 100 mg/kg increased the ileal mucosa expression of claudin 5 () (  = 0.023) and (  = 0.001) genes, and at 150 mg/kg decreased cecal (  = 0.022) gene expression compared with the un-supplemented controls. In conclusion, cereal type and PFA affected in combination and independently broiler gut microbiota composition and metabolic activity as well as the expression of critical gut barrier genes including . Further exploitation of these properties in cases of stressor challenges is warranted.