Sub-therapeutic antibiotics are widely used as growth promoters in the poultry industry; however, the resulting antibiotic resistance threatens public health. A plant-derived growth promoter, Macleaya cordata extract (MCE), with effective ingredients of benzylisoquinoline alkaloids, is a potential alternative to antibiotic growth promoters. Altered intestinal microbiota play important roles in growth promotion, but the underlying mechanism remains unknown. We generated 1.64 terabases of metagenomic data from 495 chicken intestinal digesta samples and constructed a comprehensive chicken gut microbial gene catalog (9.04 million genes), which is also the first gene catalog of an animal’s gut microbiome that covers all intestinal compartments. Then, we identified the distinctive characteristics and temporal changes in the foregut and hindgut microbiota. Next, we assessed the impact of MCE on chickens and gut microbiota. Chickens fed with MCE had improved growth performance, and major microbial changes were confined to the foregut, with the predominant role of Lactobacillus being enhanced, and the amino acids, vitamins, and secondary bile acids biosynthesis pathways being upregulated, but lacked the accumulation of antibiotic-resistance genes. In comparison, treatment with chlortetracycline similarly enriched some biosynthesis pathways of nutrients in the foregut microbiota, but elicited an increase in antibiotic-producing bacteria and antibiotic-resistance genes. The reference gene catalog of the chicken gut microbiome is an important supplement to animal gut metagenomes. Metagenomic analysis provides insights into the growth-promoting mechanism of MCE, and underscored the importance of utilizing safe and effective growth promoters.

The present study was carried out to evaluate the pharmacological effect of Zn in diarrhoea in relation to intestinal permeability. Seventy-two weaning piglets, aged 24 d, were allocated to three dietary treatments: (1) control diet without supplemental Zn; (2) control diet supplemented with 2000 mg Zn/kg from ZnO; (3) control diet supplemented with 2000 mg Zn/kg from tetrabasic zinc chloride (TBZC). At the end of a 14 d experiment period, piglets were weighed, feed consumption was measured, and mucosal barrier function was determined using the lactulose/mannitol test. Expression of mucosal tight junction protein was measured at RNA and protein level. Inclusion of TBZC or ZnO in the diet significantly increased average daily gain (P < 0·01) and average daily feed intake (P < 0·05), while leading to reduced feed conversion ratio (P < 0·05) and faecal scores (P < 0·01). TBZC reduced urinary lactulose:mannitol ratios of weaning piglets (P < 0·05), while dietary supplementation with ZnO tended to reduce urinary lactulose:mannitol ratios (P = 0·061). ZnO or TBZC significantly enhanced the mRNA and protein expression of occludin (P < 0·05) and zonula occludens protein-1 (ZO-1) (P < 0·05) in the ileal mucosa. Piglets fed the TBZC-supplemented diet had a higher level of occludin than pigs fed the ZnO-supplemented diet (P < 0·05). The results indicate that Zn supplementation decreased faecal scores and the reduction was accompanied by reduced intestinal permeability, which was evident from the reduced urinary lactulose:mannitol ratios and increased expression of occludin and ZO-1. Therefore, the protective effect of pharmacological levels of dietary Zn in reducing diarrhoea might, at least partly, be associated with reduced intestinal permeability.

Necrotic enteritis caused by Clostridium perfringens infection leads to serious economic losses in the global poultry production. In the present study, we investigated the protective effects of essential oils (EO, which contained 25 % thymol and 25 % carvacrol as active components) supplementation on growth performance, gut lesions, intestinal morphology, and immune responses of the broiler chickens infected with C. perfringens. A total of 448 1-day-old male broiler chicks were allocated into eight treatment groups following a 4 × 2 factorial arrangement with four dietary EO dosages (0, 60, 120, or 240 mg/kg) and two infection status (with or without C. perfringens challenge from d 14 to 20). The challenge did not impair the growth performance of birds, but induced gut lesions and increased crypt depth in the ileum (P ≤ 0.05). It also down-regulated the claudin-1 and occludin mRNA expression (P ≤ 0.05), up-regulated the mRNA expression of interleukin-1β (P ≤ 0.05), tended to increase the toll-like receptor (TLR) 2 mRNA expression (P < 0.10) in the ileum, and enhanced the mucosal secretory IgA production (P ≤ 0.05). In the challenged birds, dietary EO supplementation linearly alleviated the gut lesions and improved the ratio of villus height to crypt depth (P ≤ 0.05), and the supplementation of 120 and 240 mg/kg EO increased the serum antibody titers against Newcastle disease virus (P ≤ 0.05). Regardless of challenge, the EO supplementation showed a tendency to linearly elevate the feed conversion efficiency between 14 and 28 d of age as well as the occludin mRNA expression (P < 0.10), and linearly inhibited the mRNA expression of TLR2 and tumor necrotic factor-α in the ileum (P ≤ 0.05). The dietary supplementation of EO could alleviate the intestinal injury by improving intestinal integrity and modulating immune responses in the C. perfringens-challenged broiler chickens.

In the post-antibiotic era, essential oils (EO) are promising alternatives to growth-promoting antibiotics. The aim of the present study was to investigate the antibacterial activities of an EO product and its components thymol and carvacrol in vitro, and the efficacy of EO to control Clostridium perfringens challenge in broiler chickens. The in vitro minimum inhibitory concentration assay showed strong antibacterial activity of the EO product, thymol, and carvacrol against pathogenic Escherichia coli, C. perfringens, and Salmonella strains, and weak activity towards beneficial Lactobacillus strains. Besides, an additive effect was observed between thymol and carvacrol. The in vivo study was carried out with 448 male broiler chicks following a 4 × 2 factorial arrangement to test the effects of EO supplementation (0, 60, 120, or 240 mg/kg EO in wheat-based diet), pathogen challenge (with or without oral gavage of C. perfringens from day 14 to day 20) and their interactions. Each treatment consisted of eight replicate pens (seven birds/pen). The challenge led to macroscopic gut lesions, and resulted in a significant increase in ileal populations of C. perfringens and Escherichia subgroup (P ≤ 0.05) on day 21. Dietary EO supplementation did not influence C. perfringens numbers, but linearly alleviated intestinal lesions on day 21 and 28 (P = 0.010 and 0.036, respectively), and decreased Escherichia populations in ileum with increased EO dosages (P = 0.027 and 0.071 for day 21 and 28, respectively). For caecum, EO quadratically influenced Lactobacillus populations on day 21 (P = 0.002), and linearly decreased the numbers of total bacteria and Escherichia on day 28 (P = 0.026 and 0.060, respectively). Mean thymol and carvacrol concentrations in the small intestine were 0.21 and 0.20 μg/g in intestinal digesta (wet weight), respectively, for birds fed 60 mg/kg EO, and 0.80 and 0.71 μg/g, respectively, for birds fed 240 mg/kg EO. These results indicated that dietary EO supplementation could affect intestinal microbiota and alleviate intestinal lesions in broilers, which may contribute in controlling C. perfringens infection in broiler chickens.

Background: There are many diseases in poultry, many of which are caused by poor immune function. It is not clear how cytokines and various immune cell functions change with age in modern broilers. The purpose of this study was to explore the patterns of development of the immunity of the broiler chickens in cage.Results: The results showed that there were 3 development patterns of immunity in the broiler chickens. The first pattern was Down-Up. Cytokines and some immune indicators first decreased and then increased, and the lowest levels of immunity basically occurred from d 6 to 13. The second pattern was Up-Down, and from d 30 to 34, the highest levels of non-specific cellular immunity components, such as the peripheral blood mononuclear macrophage ratio, specific cellular immunity components, such as the peripheral blood helper T (Th) cell ratio and T cell and B cell proliferation activity, and mucosal immunity components, such as the ilealCD4,TGF-β1andIgAmRNA levels, were observed. The third pattern was Up-Up, and the levels of the non-specific cellular immunity components, such as the serum nitric oxide (NO), C3 and C4 levels, the specific cellular immunity components, such as the spleen index, peripheral blood IL-2, IFN-γ/IL-4, cytotoxic T (Tc) cell ratio, and splenicNF-κBmRNA levels, the humoral immunity components, such as the serum IgG level, the mucosal immunity components, such as the ilealMHC-II, CD3d, TCRβ subunit, TCRζ subunit, IFN-γ, pIgRmRNA and ileal mucosa sIgA levels, were continuing to increase from d 1 to 34.Conclusions: It could be concluded that the immune system and its function have not developed well in the broiler chickens d 6 to 13 and that the immune system does not mature until d 30 to 34 in the broiler chickens in cages. It is necessary to enhance the immune function of the broiler chickens through nutritional measures from d 1 to 30.

The effects of live yeast (LY) and mannan-oligosaccharide (MOS) supplementation on intestinal disruption induced by Escherichia coli in broilers were investigated. The experimental design was a 3×2 factorial arrangement with three dietary treatments (control, 0·5 g/kg LY (Saccharomyces cerevisiae, 1·0×10¹⁰ colony-forming units/g), 0·5 g/kg MOS) and two immune treatments (with or without E. coli challenge from 7 to 11 d of age). Samples were collected at 14 d of age. The results showed that E. coli challenge impaired (P<0·05) growth performance during the grower period (1–21 d) and the overall period (1–35 d) of broilers, increased (P<0·05) serum endotoxin and diamine oxidase levels coupled with ileal myeloperoxidase and lysozyme activities, whereas reduced (P<0·05) maltase activity, and compromised the morphological structure of the ileum. Besides, it increased (P<0·05) the mRNA expressions of several inflammatory genes and reduced occludin expression in the ileum. Dietary treatment with both LY and MOS reduced (P<0·05) serum diamine oxidase and ileal myeloperoxidase levels, but elevated villus height (P<0·10) and the ratio of villus height:crypt depth (P<0·05) of the ileum. It also alleviated (P<0·05) E. coli-induced increases (P<0·05) in ileal Toll-like receptor 4, NF-κB and IL-1β expressions. Moreover, LY supplementation reduced (P<0·05) feed conversion ratio of birds during the grower period and enhanced (P<0·05) the community diversity (Shannon and Simpson indices) of ileal microbiota, whereas MOS addition counteracted (P<0·05) the decreased ileal IL-10 and occludin expressions in challenged birds. In conclusion, both LY and MOS supplementation could attenuate E. coli-induced intestinal disruption by alleviating intestinal inflammation and barrier dysfunction in broilers. Moreover, LY addition could improve intestinal microbial community structure and feed efficiency of broilers.