Diet supplementation with an organic acids-based formulation affects gut microbiota and expression of gut barrier genes in broilers

This study was designed to study the effect of diet supplementation with an organic acids-based formulation (OABF) on luminal- and mucosa-associated bacteria, concentration of volatile fatty acids (VFA), microbial glycolytic enzyme activity and expression of mucin 2 (MUC2), immunoglobulin A (IgA) and tight junction protein, i.e., zonula occludens-1 (ZO1), zonula occludens-2 (ZO2), claudin-1 (CLDN1), claudin-5 (CLDN5) and occludin (OCLN), genes at the ileal and cecal level. A 2 × 2 factorial design was used having OABF inclusion and avilamycin as main factors. Subsequently, 544 day-old male Cobb broilers were allocated in the following 4 treatments, each with 8 replicates: no additions (CON), 1 g OABF/kg diet (OA), 2.5 mg avilamycin/kg diet (AV) and combination of OA and AV (OAAV). The trial lasted for 42 days. In the ileum, OAAV resulted in lower mucosa-associated total bacteria levels (P(O × A) = 0.028) compared with AV. In addition, ileal digesta levels of Clostridium perfringens subgroup were decreased by avilamycin (P(A) = 0.045). Inclusion of OABF stimulated the activity of microbial glycolytic enzymes, whereas avilamycin resulted in lower acetate (P(A) = 0.021) and higher butyrate (P(A) = 0.010) molar ratios. Expression of ZO1 and CLDN5 was down-regulated by both OABF (P(O) = 0.016 and P(O) = 0.003, respectively) and avilamycin (P(A) = 0.016 and P(A) = 0.001, respectively). In addition, CLDN1 was down-regulated in AV compared with CON (P(O × A) = 0.012). Furthermore, OABF down-regulated MUC2 (P(O) = 0.027), whereas avilamycin down-regulated nuclear factor kappa B subunit 1 (NFKB1) (P(A) = 0.024), toll-like receptor 2 family member B (TLR2B) (P(A) = 0.011) and toll-like receptor 4 (TLR4) (P(A) = 0.014) expression. In the ceca, OABF inclusion increased digesta levels of Clostridium coccoides (P(O) = 0.018) and Clostridium leptum (P(O) = 0.040) subgroups, while it up-regulated MUC2 expression (P(O) = 0.014). Avilamycin (P(A) = 0.044) and interaction (P(O × A) < 0.001) effects for IgA expression were noted, with CON having higher IgA expression compared with AV. In conclusion, new findings regarding OABF inclusion effects on an array of relevant biomarkers for broiler gut ecology have been reported and discussed in parallel with avilamycin effects used as a positive control. This new knowledge is expected to provide a response baseline for follow up trials under various stress and challenge conditions.