Background: The poultry industry is in need of effective antibiotic alternatives to control outbreaks of necrotic enteritis (NE) due to Clostridium perfringens. In the present study, we investigated the effects of dietary supplementation with a blend of encapsulated essential oils and organic acids (BLJ) on growth performance and gut health using a coinfection model of NE in broiler chickens. Methods: Two hundred and eighty-eight one-day-old male Arbor Acres broiler chicks were randomly assigned using a 2 × 2 factorial design into two groups fed either 0 or 500 mg/kg dietary BLJ and co-challenged (or not challenged for the control) with Eimeria spp./C. perfringens. Results: Infected birds fed the BLJ-supplemented diet exhibited an improved feed conversion ratio throughout the trial (P < 0.01), a higher villus height and villus height/crypt depth ratio, and reduced intestinal C. perfringens counts, liver C. perfringens carriage, gut lesion scores and serum fluorescein isothiocyanate dextran (FITC-D) concentrations at 7 d postinfection compared with those of birds without BLJ supplementation (P < 0.05). NE-infected birds fed BLJ exhibited significantly upregulated claudin-1 and IGF-2 mRNA levels (P < 0.05), increased A20 mRNA expression and significantly downregulated TRAF-6, TNFSF15 and TOLLIP mRNA levels in the jejunum at 7 d post-infection compared with those in birds without BLJ supplementation (P < 0.05). Compared with the uninfected and untreated birds, the uninfected birds fed BLJ displayed increased relative abundances of Lactobacillus and Coprococcus but reduced Rikenellaceae levels. Compared with the unsupplemented NE-challenged birds, infected birds fed BLJ showed an increased relative abundance of Unclassified_ Lachnospiraceae and a significantly decreased relative abundance of Erysipelotrichaceae. Conclusion: BLJ supplementation improved growth performance and gut health in NE-infected broiler chickens by strengthening the intestinal barrier function, positively modulating the gut microbiota community and differentially regulating intestinal immune responses. Our results also suggested that adding BLJ effectively controlled NE infections after experimental Eimeria and Clostridium perfringens coinfection.

Necrotic enteritis infection poses a serious threat to poultry production, and there is an urgent need for searching effective antibiotic alternatives to control it with the global ban on in-feed antibiotics. This study was conducted to investigate the effects of dietary Bacillus licheniformis replacing enramycin on the growth performance and intestinal health of subclinical necrotic enteritis (SNE)-challenged broilers. In total, 504 1-day-old Arbor Acres male chickens were selected and subsequently assigned into three treatments, including PC (basal diet + SNE challenge), PA (basal diet extra 10 mg/kg enramycin + SNE challenge), and PG (basal diet extra 3.20 × 109 and 1.60 × 109 CFU B. licheniformis per kg diet during 1–21 days and 22–42 days, respectively + SNE challenge). Results showed that B. licheniformis significantly decreased the intestinal lesion scores and down-regulated the Claudin-3 mRNA levels in jejunum of SNE-infected broilers on day 25, but increased the mucin-2 gene expression in broilers on day 42. In addition, B. licheniformis significantly up-regulated the mRNA levels of TRIF and NF-κB of SNE-challenged broilers compared with the control group on day 25 and TLR-4, TRIF compared with the control and the antibiotic group on day 42. The mRNA expression of growth factors (GLP-2 and TGF-β2) and HSPs (HSP60, HSP70, and HSP90) were up-regulated in B. licheniformis supplementary group on days 25 and 42 compared with group PC. LEfSe analysis showed that the relative abundance of Lachnospiraceae_UCG_010 was enriched in the PG group; nevertheless, Clostridiales_vadinBB60 and Rnminococcaceae_NK4A214 were in PA. PICRUSt analysis found that the metabolism of cofactors and vitamins, amino acid metabolism, and carbohydrate metabolism pathways were enriched, whereas energy metabolism, membrane transport, cell motility, and lipid metabolism were suppressed in B. licheniformis-supplemented groups as compared with the PC control. In conclusion, dietary supplementation of B. licheniformis alleviated the intestinal damage caused by SNE challenge that coincided with modulating intestinal microflora structure and barrier function as well as regulating intestinal mucosal immune responses.