Background: The poultry industry needs effective antibiotic alternatives to control outbreaks of necrotic enteritis (NE) caused by Clostridium perfringens. Methods: The aim of this study was to investigate the effects of dietary supplementation with Macleaya cordata extract (MCE) on the immune function and gut microbiota of broilers with NE. A total of 288 1-day-old broiler chicks were randomly assigned to a 2 × 2 factorial arrangement with two concentrations of dietary MCE supplementation (0 or 350 mg/kg of diet) and two disease challenge statuses (control or NE). Results: The results revealed that NE significantly increased the feed conversion rate (FCR), mortality, intestinal lesion score, the levels of IL-1β, IL-17 and IFN-γ/IL-4 in serum and IL-17/IL-10 in the jejunal mucosa, mRNA levels of TLR2, IFN-γ and pIgR in the jejunum, and Clostridium perfringens concentrations in the cecum. NE significantly decreased the body weight (BW), body weight gain (BWG), jejunal villus height, V/C, mRNA level of AMPK-α1 in jejunum, IL-4 level in the jejunal mucosa and lactic acid bacteria abundance in the cecum. MCE significantly increased BW, BWG, jejunal villus height, V/C, mRNA levels of occludin, ZO-1 and AMPK-α1 in the jejunum, the levels of IgA and IgG in serum and IL-10 in the jejunal mucosa and mRNA levels of NF-κB, IL-10 and MHC-II in the jejunum. Additionally, MCE significantly decreased the FCR, mortality, intestinal lesion score, jejunal crypt depth, the levels of IFN-γ and IL-17 in serum and IL-17/IL-10 in the jejunal mucosa, Clostridium perfringens concentrations in the cecum, and mRNA levels of IL-17/IL-10 in the jejunum. Moreover, NE significantly increased the abundance of bacteria that are associated with inflammation, obesity and depression (Alistipes, Barnesiella, Intestinimonas, RF39 and UCG-005) and significantly decreased the abundance of short-chain fatty acid (SCFA)-producing bacteria (Anaerotruncus, Butyricicoccus and Bacteroides) in the cecum. MCE significantly increased the abundance of SCFA-producing bacteria (Streptococcus, Ruminococcus_torques_group and Lachnospiraceae_NK4A136_group) and significantly reduced the abundance of bacteria that are associated with inflammation and obesity (Alistipes, Barnesiella and UCG-010) in the cecum. In the cecum of broilers with NE, the relative abundance of Barnesiella and Alistipes was higher and that of Lachnoclostridium and Shuttleworthia was lower. Interestingly, these trends were reversed by the addition of MCE to the diet. Spearman correlation analysis showed that Barnesiella and Alistipes were associated with enhanced intestinal inflammation and inhibited growth performance, whereas Lachnoclostridium and Shuttleworthia were associated with anti-inflammatory effects. Conclusions: MCE ameliorated the loss of growth performance in broiler chickens with NE, probably by regulating the intestinal barrier, immune function, and gut microbiota.

The study investigated the effects of dietary probiotic of dual-strain Bacillus subtilis on production performance, intestinal barrier parameters, and microbiota in broiler chickens. In a randomized trial, male broiler chickens were allocated into 3 groups, a control group (basal diet), BS300 group (basal diet with 300 mg/kg of B. subtilis), and BS500 group (basal diet with 500 mg/kg of B. subtilis). The inclusion of 500 mg/kg of B. subtilis significantly reduced the feed conversion ratio by 4.55% during the starting phase. Both 300 and 500 mg/kg of B. subtilis supplementation increased jejunal villus height (by 17.89% and 24.8%, respectively) significantly and decreased jejunal crypt depth (by 27.2% and 31.9%, respectively) on day 21. The addition of 500 mg/kg of B. subtilis significantly elevated the gene expression of occludin on day 35. Moreover, of B. subtilis supplementation enhanced cytokine levels and immunoglobulins in both serum and jejunal mucosa. Microbial analysis indicated that B. subtilis increased the abundance of potential probiotics (Sutterella) and butyrate-producing bacteria (Lachnoclostridium, Tyzzerella, Anaerostipes, Clostridium_sensu_stricto_13, Prevotellaceae_NK3B31_group, and Lachnospiraceae_UCG-010). The abundances of Anaerostipes and Sutterella, are significantly correlated with growth performance and immune function. In conclusion, dietary supplementation with B. subtilis improved the growth performance, potentially through the regulation of immunity, intestinal barrier function, and microbiota in broilers. Notably, 500 mg/kg of B. subtilis exhibited more benefits for broilers compared to the 300 mg/kg. Bacillus emerges as a promising probiotic candidate, offering a suitable alternative to antibiotics in animal feed. However, previous research predominantly focused on single-strain Bacillus, with limited exploration into dual-strain Bacillus subtilis-based probiotics. This study demonstrates that dietary supplementation with dual-strain B. subtilis enhances feed conversion ratio, intestinal morphology, gene expression related to tight junction proteins, Th1-like cytokines, immunoglobulins, as well as the abundance of potential probiotics (Sutterella) and butyrate-producing bacteria (Anaerostipes, Tyzzerella, UCG-010, etc.) in the cecum. The abundances of Anaerostipes and Sutterella, are significantly correlated with growth performance and immune function. These findings lay a foundation for incorporating dual-strain B. subtilis-based probiotics in broiler feed.

This study was conducted to investigate the effects of Romboutsia (R.) ilealis on the immune function of broilers and the underlying mechanisms. A total of 48 one-d-old Arbor Acres broilers were allocated to 4 groups as follows: broilers treated daily with 1 mL live R. ilealis in GAM broth media (0, 1×10⁴, 1×10⁶ and 1×10⁸ CFU/mL) from d 1 to 7. Samples were collected on d 8 and 14. The results showed that R. ilealis had no negative effect on the body weight of broilers (P > 0.05). R. ilealis significantly increased the levels of lysozyme, IFN-γ, IFN-γ/IL-4, and IgG in the serum (P < 0.05). R. ilealis significantly increased the levels of IL-4, IFN-γ, sIgA, lysozyme, and iNOS in the ileal mucosa (P < 0.05). R. ilealis significantly increased the mRNA levels of TLR2, TLR4, NF-κB, IL-1β, TNF-α, IFN-γ, IgA, pIgR, iNOS, and MHC-Ⅱ in the ileum (P < 0.05). R. ilealis significantly increased the relative abundance of Enterococcus and Paracoccus in the jejunum and ileum, ileal Candidatus Arthromitus, and cecal Romboutsia and Intestinimonas (P < 0.05). Correlation analysis showed that Enterococcus, Paracoccus, Romboutsia, and Intestinimonas were significantly positively correlated with humoral immune function (P < 0.05). In conclusion, Romboutsia ilealis boosted the immune system, activated the intestinal TLR2/NF-κB signaling pathway, and improved the gut microbiota in broilers.

This study aimed to investigate the effects of dietary sodium butyrate (SB) supplementation on the reproductive performance of female broiler breeders under intensive rearing conditions and to analyze antioxidant capacity, immune function, and intestinal barrier function of the female breeders and their offspring. A total of 96,000 40-wk-old Ross308 female broiler breeders were divided into the control (CON) and SB groups, each with 6 replicates of 8,000 birds. Each house with similar production performance characteristics was considered a replicate. The experiment lasted for 20 wk, whereupon sampling took place. Results showed that SB improved the egg production performance, egg quality of broiler breeders, and hatchability (P < 0.05). Maternal supplementation with SB substantially increased serum immunoglobulin A levels in broiler breeders and offspring (both P = 0.04) and offspring immunoglobulin G (P < 0.001). The levels of interleukin-1β (P < 0.001) and interleukin-4 (P = 0.03) in the offspring were downregulated, while the total superoxide dismutase in the offspring and the eggs increased (P < 0.05). The serum biochemical components in breeders and offspring were altered by SB, as evidenced by the reduction in triglycerides, total cholesterol, and high- and low-density lipoproteins (P < 0.05). The intestinal morphology of broiler breeders and offspring also improved by the SB with the decreasing the jejunal crypt depth (P = 0.04) and increasing villus height in offspring (P = 0.03). Maternal jejunal and ileal intestinal barrier-related genes were also shown to be significantly affected by SB. Furthermore, SB altered the microbial diversity in maternal cecal contents, thus increasing the abundance of Lachnospiraceae (P = 0.004) and Ruminococcaceae (P = 0.03). Dietary SB enhanced the reproductive performance and egg quality of broiler breeders and improved the antioxidant capacity and immune function of broiler breeders and offspring, with the benefits potentially arising from the regulation of the maternal intestinal barrier and gut microbiota by SB.

To investigate the change in zinc homeostasis of broilers under heat stress, 512 broiler chickens were raised to the age of 28 days. The broilers were then assigned to heat stress and normal temperature (36.0°C vs. 26.0°C) groups for 7 days. The results showed that oxidative stress induced by high temperature had a negative effect on the growth performance of broilers. Heat stress altered zinc homeostasis and led to a redistribution of zinc in broilers, which was reflected in increased zinc concentrations in the jejunum, liver, and tibia. Upregulation of the expression of the zinc exporter ZnT1 and importers ZIP8 and ZIP14 in the jejunum indicated that more zinc was absorbed and transported from the jejunum into the blood, while the liver increased its capacity to hold zinc through upregulation of metallothionein (MT) expression, which was achieved by reducing ZnT1 expression and upregulating the expression of the importer ZIP3. The pathway was mediated by zinc transporters, but the capacity of MT to chelate and release zinc ions also played a crucial role. The mechanism of alterations in zinc homeostasis under heat stress was revealed by the changes in zinc transporters and MT levels in the intestine and liver. Heat stress also altered cecal microbial diversity and reduced the relative abundances of Bilophila and Dialister. In conclusion, broilers altered systemic zinc homeostasis through the regulation of zinc transporters and MT in the liver and jejunum to resist oxidative stress induced by high temperature.

The effects of dietary Bacillus subtilis (BS) on the meat quality of broilers were evaluated, with an emphasis on the regulation of muscle fiber types and antioxidant capabilities. One hundred and forty-four Arbor Acres male broilers were divided into 3 treatment groups (0, 300 mg/kg and 500 mg/kg dietary BS) and raised for 35 d. The results suggested that BS improved meat quality by improving the muscular pH, meat color, water holding capacity and shear force. Immunofluorescence staining revealed a positive impact of BS on the muscle fiber transformation in thigh muscles, and the gene/protein expression data from specific muscle fiber types confirmed this finding. BS activated AMP-activated protein kinase (AMPK), silent information regulator 1 and peroxisome proliferator-activated receptor gamma coactivator 1alpha. The postmortem analysis revealed that BS increased the activity of glutathione peroxidase and total antioxidant capacity while decreasing the malondialdehyde content. Additionally, BS increased the gene and protein expression of nuclear factor-like 2 (Nrf2) and activated the Nrf2 signaling pathway, including its downstream factors, such as heme oxygenase-1, catalase, superoxide dismutase and glutathione peroxidase. In conclusion, dietary BS improved meat quality by modifying muscle fiber types and enhancing the antioxidant capacity in broilers.