Background: In broiler chickens, necrotic enteritis (NE) infection can reduce production performance. Tannic acid has shown great potential as a treatment of NE in broilers. However, the appropriate dosage of tannic acid in NE of broilers and the improvement effect on intestinal health are not very clear. In this study, we aimed to investigate the effects of different doses of tannic acid on the production performance, immunity, and intestinal health of broilers by constructing an NE model with C. perfringens infection and determining the appropriate dosage of tannic acid with regard to NE. Results: Challenged birds showed significant reduction in body weight, villus height, and the ratio of villus height to crypt depth (P < 0.05) and increase in the feed consumption gain ratio, intestinal lesion score, and crypt depth (P < 0.05). The infection significantly reduced the relative Bacteroidota and Ligilactobacillus abundance (P < 0.05) and increased the ratio of Firmicutes/Bacteroidota and cecal content of C. perfringens (P < 0.05). Challenged birds fed diets supplemented with tannic acid showed significantly increased mRNA expression of nutrient transport carriers and intestinal barrier genes and growth performance and reduced serum zonulin and endotoxin levels (P < 0.05). Addition of tannic acid to the diet inhibited the inflammatory response by reducing the number of coccidia oocysts in feces and the content of C. perfringens in the cecum. Specifically, tannic acid reduced the serum levels of C reactive protein, myeloperoxidase, and specific IgY and ileal mucosal secretory immunoglobulin A levels in the ileal mucosa compared with those in the NE-infected birds. NE-infected birds fed diets supplemented with tannic acid also showed significantly increased relative Anaerocolumna, Thermoanaerobacterium, and Thermosinus abundance (P < 0.05); their microbial composition and functional predictions were similar to those of the NC group. Conclusions: Tannic acid in the diet alleviated NE by enhancing the intestinal barrier and absorption function. The recommended dietary tannic acid additive level is 500–750 mg/kg. Our study findings would be useful in reducing related economic losses in the broiler industry.

Background: In China, cage systems with a high space utilization have gradually replaced ground litter systems, but the disease incidence of chickens in cages is higher. Broilers in the ground litter pens may be stimulated by more environmental microbes during the growth process and show strong immune function and status, but knowledge of which microbes and their metabolites play an immunomodulatory role is still limited. This study aimed to explore the differences and correlations in the immune function, gut microbiota and metabolites and the importance of gut microbiota of broilers raised in cages and ground litter pens. Methods: The experiment involved a 2 × 2 factorial arrangement, with rearing systems (cages or ground litter pens) and antibiotic treatment (with or without broad-spectrum antibiotics in drinking water) as factors. Results: The results showed that, compared with the cage group, the ground litter broilers had stronger nonspecific immune function (Macrophages% and NO in blood), humoral immune function (IgG in blood, LPS stimulation index in ileum) and cellular immune function (T%, Tc%, ConA stimulation index and cytokines in blood). Antibiotic (ABX) treatment significantly reduced nonspecific immune function (Macrophages% and NO in blood, iNOS and Mucin2 mRNA expression in ileum), humoral immune function (IgG in blood and sIgA in ileum) and cellular immune function (T% and cytokines in blood, Th and Tc ratio, TLRs and cytokines mRNA expression in ileum). Furthermore, the ground litter broilers had higher α diversity of microbiota in ileum. The relative abundance of Staphylococcus, Jeotgalicoccus, Jeotgalibaca and Pediococcus in the ileum of ground litter broilers were higher. ABX treatment significantly reduced the α diversity of ileal microbiota, with less Chloroplast and Mitochondria. In addition, the levels of acetic acid, isobutyric acid, kynurenic acid and allolithocholic acid in the ileum of ground litter broilers were higher. Spearman correlation analysis showed that Jeotgalibaca, Pediococcus, acetic acid, kynurenic acid and allolithocholic acid were related to the immune function. Conclusions: There were more potential pathogens, litter breeding bacteria, short-chain fatty acids, kynurenine, allolithocholic acid and tryptophan metabolites in the ileum of broilers in ground litter pens, which may be the reason for its stronger immune function and status.

Background: Soya saponin (SS), an active compound in soybean meals, has been widely studied in the medical field. However, it was considered as an anti-nutritional factor in poultry diets. The objective of this experiment was to measure the effects of dietary SS using three dietary treatments on egg-laying performance and immune function of laying hens. Birds were fed a low soybean meal basal diet (CON), a low-SS diet (50 SS) containing 50 mg/kg SS, or a high-SS diet (500 SS) containing 500 mg/kg SS for 10 weeks. At the end of the 5th and 10th week of the trial, samples were collected for analysis. Results: Results showed that with 50 mg/kg SS supplementation, the egg production rate, feed conversion ratio (FCR), and eggshell quality tended to be improved. Serum follicle stimulating hormone (FSH) and Interleukin-4 (IL-4) levels were also elevated as well as the peripheral blood LPS stimulation index, the proportion of B lymphocytes, and antibody titer of bovine serum albumin (BSA). We also found that mRNA levels of follicle stimulating hormone receptor (FSHR) in ovarian, nuclear transcription factor kappa B (NF-κB), Transforming growth factor (TGF-β) and interferon γ (IFN-γ) in spleen were up-regulated at the end of the trial. Additionally, dietary 50 mg/kg SS improved the ileal flora via up-regulating the relative abundance of Lactobacillus, Romboutsia and Lactobacillus delbrueckii. Although the immune related indicators were improved with 500 mg/kg SS supplemented, it seemed to have a negative influence on the laying-performance. Specifically, serum alanine aminotransferase (ALT), alkaline phosphatase (ALP), and the ratio of IFN-γ to IL-4 were increased in the 500 SS group at the end of the trial. The mRNA levels of gonadotropin releasing hormone 1 (GnRH1) in Hypothalamus, the estrogen related receptor (ERR) in ovaries were downregulated as well as the egg production rate during the trial with 500 mg/kg SS supplemented. Conclusions: The egg production performance was improved by dietary supplemented with 50 mg/kg SS via increasing ovarian FSHR transcription level and serum estrogen level. A beneficial shift in intestinal microflora was recorded, and the immune function of laying hens was also improved with 50 mg/kg SS supplementation. Surprisingly, the long-term supplementation of 500 mg/kg SS exerted a negative impact on the laying performance and physiological functions of the liver of laying hens.

Soya saponins (SS) have the ability to improve the intestinal microbiota and enhance intestinal immune function. While, there are few reports on their application in broiler production. The present study was designed to investigate effects of dietary supplementary with SS on the intestinal health of birds challenged with coccidia (CC). 180 male and healthy Cobb 500 broiler chickens with unifrom body weight were randomly divided into 3 treatment groups, those groups were named as the control group (CTR), the coccidia challenged group (CC), and the SS treated group challenged with CC (SS+CC). There were 6 replicates in each group, and 10 birds in each replicate. Birds in the CTR and CC group were fed with the basic diet, and birds in the SS+CC group were fed with the basic diet supplemented with 200 mg/kg SS. The animal trial lasted for 21 days, on day 10 and 12, birds in the CC and SS+CC group were challenged with CC, and birds in the CTR group were treated with normal saline, samples were harvested on day 14, and the growth performance from day 1 to day 10 as well as from day 1 to day 21 were recorded. Outcomes showed that the body weight (BW), average daily weight gain (ADG) and average daily feed intake (ADFI) were descended, and the feed conversion ratio (FCR) was elevated with CC challenged (P < 0.05). The villi height (VH) and the ratio of VH to crypt depth (CD) in jejunum and ileum were decreased with CC challenged, as well as the levels of ileal secretory immunoglobulin A (sIgA) and acetic acid in the ileal chyme (P < 0.05). Additionally, the mRNA level of ileal occludin was down-regulated, the transcriptional levels of ileal IL-8, interferon-γ (IFN-γ), cysteine-dependent aspartate-specific protease-1 (Caspase-1), and induced NO synthase (i-NOS) were up-regulated with CC challenged (P < 0.05). Dietary supplementary with SS tended to improve the FCR from day 1 to day 10 (P = 0.06), and was able to alleviated the above-mentioned negative effects induced by CC. Interestingly, dietary supplementary with SS contributed to reshaping the structure of the intestinal microbiota, specifically, reshaping the abnormal changes in the abundance of Lactobacillus and Romboutsia in the ileal chyme challenged with CC (P < 0.05). It was worth mentioning that the relative abundance of Lactobacillus was positively correlated with the levels of short-chain fatty acids in the ileal chyme, and it of Romboutsia was positively correlated with the mRNA levels of ileal IL-8, IFN-γ, Caspase-1, and i-NOS (P < 0.05). In conclusion, dietary supplementary with SS alleviated the poor intestinal health of broilers caused by CC via reshaping the structure of the intestinal microbiota.

Probiotics have great potential in maintaining intestinal health and ensuring the growth performance of broiler chickens, while the effects of Bacillus velezensis (BV) have not yet been fully characterized. In the present study, a necrotic enteritis model was established based on the combined infection of coccidia and Clostridium perfringens (CCP), and the effects of dietary supplementation with BV on growth performance and intestinal health were investigated. Our outcomes showed that dietary supplementation with BV contributed to alleviating the negative effects of CCP on the growth performance. Additionally, the ratio of ileal villus height to crypt depth, the levels of d-xylose and lysozyme in serum, as well as that of secretory immunoglobulin A (sIgA) in ileum were decreased, and the activity of diamine oxidase (DAO) was elevated with CCP challenged (P < 0.05). In addition, the level of ileal malondialdehyde (MDA), transcriptional levels of IL-1β and interferon-γ (IFN-γ) were up-regulated, correspondingly, the ileal total antioxidant capacity (T-AOC) and the mRNA levels of transforming growth factor-β (TGF-β), lysozyme (LYZ), Claudin-1, and Mucin-2 were down-regulated with CCP challenged (P < 0.05). Interestingly, the BV-supplemented diet was able to alleviate the above-mentioned negative effects of CCP on birds. The results of intestinal microbiota sequencing and association analysis further revealed that dietary supplementation with BV helped to enhance the energy utilization efficiency of the intestinal flora and might alleviate the impaired intestinal function of birds challenged with CCP by reshaping intestinal flora, especially through modulating the relative abundance of Clostridium. In conclusion, the diet supplemented with BV enhances the intestinal health of broiler chickens challenged with necrotic enteritis via reshaping the structure and function of the intestinal flora.