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The objective of this study was to investigate whether dietary supplementation with benzoic acid, Enterococcus faecium, and essential oil complex (BEC) could help laying hens recover from coccidia and Clostridium perfringenstype 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 replicate): (I) control group (CON), (II) challenge group (CC), and (III) BEC group (2000mg/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 proinflammatory cytokines (IL-1β and IL-6) (P< 0.05). An increase in the abundance of Bacteroidoes(genus), Bacteroidaceae(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 Faecalibacteriumand Asterolplasmawere positively correlated with egg laying rate (r= 0.57, 0.60; P < 0.01); and the genera Bacteroidesand Romboutsiawere negatively correlated with egg-laying rate (r= -0.58, -0.74; P< 0.01). The genera Bacteroides, Lactobacillusand Rombutziawere positively correlated with jejunal mucosa pro-inflammatory factor IL-1β level (r = 0.61, 0.60, 0.59; P< 0.01), which were negatively correlated with genera Rikenbacteriaceae RC9, Faecalibacteriumand Olsenlla(r = -0.56, -0.57, -0.61; P< 0.01).There genera UCG.005 was positively correlated with pro-inflammatory factor IL-6 level in jejunal mucosa (r = 0.58; P< 0.01), which was negatively correlated with Rikenbacteriaceae 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 2000 mg/kg BEC modulated gut health by reducing gut damage scores and modulating microbial composition, thereby promoting recovery of laying hens after coccidia and Clostridium perfringenschallenge.

The purpose of this experiment is to explore the effects of dietary supplementation of benzoic acid, Enterococcus faecium, and essential oil complex (BEC) on coccidia and Clostridium perfringenschallenge in laying hens. A total of 80 Lohmann gray laying hens (35 wk old) were allocated to 4 treatments in a 2 × 2 factorial arrangement with the main effects of Clostridium perfringenstype A (CP) and coccidia challenge (with or without challenge) and 2 BEC levels (0 and 1,000 mg/kg). The total experimental period was 6 wk. The results showed that: the challenge group significantly decreased the laying rate and average daily feed intake (ADFI) of laying hens (PChallenge< 0.01). The BEC + challenge group significantly increased the laying rate and decreased the feed conversion ratio (FCR) of laying hens (PBEC< 0.05). The challenge significantly decreased the thickness, strength, and relative weight of eggshell (PChallenge< 0.05). The BCE + challenge group significantly increased the relative weight and strength of the eggshell (PBEC< 0.05). The challenge significantly increased the crypt depth of the duodenum, jejunum and ileum, and decreased the villus-to-crypt ratio (V/C) (PChallenge< 0.01). The BEC + challenge group decreased the crypt depth of the duodenum and jejunum, and increased the V/C of the duodenum (PBEC< 0.01). The pathological scores of duodenum and jejunum of the challenge group were significantly higher than other groups (PChallenge< 0.01), while the BEC + challenge group had lower pathological scores of jejunum (PBEC< 0.01). The challenge significantly decreased the mRNA expression of Occludin, Mucin-2, Zonula occluden-1 (ZO-1)(Pchallenge< 0.05); whereas the BEC group significantly increased the expression of Occludin, Mucin-2, and Claudin-1mRNA (PBEC< 0.05). The challenge significantly increased the level of interleukin 1β (IL-1β) in the jejunum (PChallenge< 0.05). Taken together, adding BEC to the diet can improved production performance and egg quality of layers, by protecting intestinal health against Clostridium perfringenstype A (CP) and coccidia challenge.