Effect of benzoic acid, Enterococcus faecium, and essential oil complex on intestinal microbiota of laying hens under coccidia and Clostridium perfringens challenge

The objective of this study was to investi-gate whether dietary supplementation with benzoic acid, Enterococcus faecium, and essential oil complex (BEC) could help laying hens recover from coccidia and Clostrid-ium perfringens type A challenge. A total of 60 (35-wk -old) Lohmann-laying hens were randomly assigned to 3 experimental groups (10 replicates with 2 hens per repli-cate): I) control group (CON), II) challenge group (CC), and III) BEC group (2,000 mg/kg BEC). The total experimental period was 8 wk. The results shown that the challenge layers had lower egg-laying rate and average daily feed intake (ADFI) (P < 0.05), and addition of BEC after challenge increased egg-laying rate (P < 0.05). The content of propionic acid (PA) and butyric acid (BA) in short-chain fatty acid (SCFA) was significantly decreased by challenge (P < 0.05). CC and BEC groups had lower villus height to crypt depth ratio (V/C) and higher pathological scores in duodenum (P < 0.05), whereas the BEC group had lower pathological scores in jejunum when compared with the CC group (P < 0.05). The challenge increased the concentration of proinflam-matory cytokines (IL-1b and IL-6) (P < 0.05). An increase in the abundance of Bacteroidoes (genus), Bac-teroidaceae (family), Bacteroidoes sp. Marseille P3166 (species), Bacteroidoes caecicola (species) was observed in the CC group, whereas the BEC group had higher abundance of Bacteroides caecigallinarum (species). The genera Faecalibacterium and Asterolplasma were posi-tively correlated with egg-laying rate (r = 0.57, 0.60; P < 0.01); and the genera Bacteroides and Romboutsia were negatively correlated with egg-laying rate (r =-0.58,-0.74; P < 0.01). The genera Bacteroides, Lactobacillus, and Rombutzia were positively correlated with jejunal mucosa proinflammatory factor IL-1b level (r = 0.61, 0.60, 0.59; P < 0.01), which were negatively correlated with genera Rikenbacteriaceae RC9, Faecalibacterium, and Olsenlla (r =-0.56,-0.57,-0.61; P < 0.01). There genera UCG.005 was positively correlated with proin-flammatory factor IL-6 level in jejunal mucosa (r = 0.58; P < 0.01), which was negatively correlated with Riken-bacteriaceae RC9 (r =-0.62; P < 0.01). The experiment results revealed that the addition of BEC to the diet restored the production performance of the laying hens. In addition, supplementation of 2,000 mg/kg BEC modu-lated gut health by reducing gut damage scores and mod-ulating microbial composition, thereby promoting recovery of laying hens after coccidia and Clostridium perfringens challenge.