Avian intestinal ultrastructure changes provide insight into the pathogenesis of enteric diseases and probiotic mode of action

Effects of Tibetan Sheep-Derived Compound Probiotics on Growth Performance, Immune Function, Intestinal Tissue Morphology, and Intestinal Microbiota in Mice

Probiotics play an important role in animal growth, immunity, and gut microbial balance and are now widely used in agriculture, food, and medicine. This study analysed the effects of different concentrations of Tibetan sheep compound probiotics on the immunity, tissue morphology, and intestinal microbiota of mice using histological, molecular, and 16S rRNA techniques. The results showed that the composite probiotics sourced from Tibetan sheep improved the growth performance of mice, increased the length of small intestinal villi and mucosal thickness, and enhanced the intestinal barrier function of mice. DZ-L and DZ-M significantly increased the mRNA expression levels of ZO-1, Occludin, and Claudin-1 mRNA. They also up-regulated IL-10 and TNF-β, and down-regulated TNF-α, IL-1β, and IL-8. The immune function of mice was enhanced, with DZ-M treatment having an extremely significant effect, while the effect of DZ-H treatment was slightly lower compared to DZ-L and DZ-M. In addition, the composition and diversity of the intestinal microbiota were modulated, and at the phylum level, the relative abundance of Firmicutes was higher in the DZ-M group, the relative abundance of Desulfobacterota, Actinobacteriota, and Patescibacteria was reduced in the probiotic complex group, and the relative abundance of Verrucomicrobiota was higher. At the genus level, the relative abundance of Muribaculaceae was higher in the DZ-L and DZ-M groups, and the relative abundance of Lachnospiraceae_NK4A136_group in the DZ-H group; and the relative abundance of Bacteroides and Roseburia in the composite probiotic group. This study can improve the reference for the development of new green feed additives instead of antibiotics, which will also further promote the development of the livestock industry.

Low dietary carbohydrate induces structural alterations in enterocytes of the chicken ileum

We investigated the role of dietary carbohydrates in the maintenance of the enterocyte microvillar structure in the chicken ileum. Male chickens were divided into the control and three experimental groups, and the experimental groups were fed diets containing 50%, 25%, and 0% carbohydrates of the control diet. The structural alterations in enterocytes were examined using transmission electron microscopy and immunofluorescent techniques for β-actin and villin. Glucagon-like peptide (GLP)-2 and proglucagon mRNA were detected by immunohistochemistry and in situ hybridization, respectively. Fragmentation and wide gap spaces were frequently observed in the microvilli of the 25% and 0% groups. The length, width, and density of microvilli were also decreased in the experimental groups. The experimental groups had shorter terminal web extensions, and there were substantial changes in the mitochondrial density between the control and experimental groups. Intensities of β-actin and villin immunofluorescence observed on the apical surface of enterocytes were lower in the 0% group. The frequency of GLP-2-immunoreactive and proglucagon mRNA-expressing cells decreased with declining dietary carbohydrate levels. This study revealed that dietary carbohydrates contribute to the structural maintenance of enterocyte microvilli in the chicken ileum. The data from immunohistochemistry and in situ hybridization assays suggest the participation of GLP-2 in this maintenance system.

Addition of a Blend Based on Zinc Chloride and Lignans of Magnolia in the Diet of Broilers to Substitute for a Conventional Antibiotic: Effects on Intestinal Health, Meat Quality, and Performance

This study aimed to determine whether adding a blend based on zinc chloride and lignans from magnolia to the diet of broilers could replace conventional performance enhancers. For this study, 360 chickens were divided into four groups, with six repetitions per group (n = 15), as follows: CN, without promoter; GPC, control, 50 mg/kg of enramycin growth promoter; T-50, additive blend at a dose of 50 g/ton; and T-100, additive blend at a dose of 100 g/ton. Chickens fed with the additive blend at 50 g/ton showed a production efficiency index equal to that in the GPC group (p < 0.05). At 42 days, the lowest total bacterial count (TBC) was found in the T-100 group, followed by that in the GPC group (p < 0.001). For E. coli, the lowest count was observed in the T-100 group, followed by that in the CP and T-50 groups (p < 0.001). Higher villus/crypt ratios were observed in birds belonging to the T-100 and T-50 groups than in the GPC and NC groups (p < 0.001). Greater water retention was found in the T-50 group than in NC and T-100 groups (p < 0.048). The lowest water loss during cooking was also noted in the T-50 group (p < 0.033). We concluded that adding the antimicrobial blend, primarily at 50 g/ton, maintains the efficiency of the index of production and improves the intestinal health and meat quality of the birds.

Host gene expression is associated with viral shedding magnitude in blue-winged teals (Spatula discors) infected with low-path avian influenza virus

Intraspecific variation in host infectiousness affects disease transmission dynamics in human, domestic animal, and many wildlife host-pathogen systems including avian influenza virus (AIV); therefore, identifying host factors related to host infectiousness is important for understanding, controlling, and preventing future outbreaks. Toward this goal, we used RNA-seq data collected from low pathogenicity avian influenza virus (LPAIV)-infected blue-winged teal (Spatula discors) to determine the association between host gene expression and intraspecific variation in cloacal viral shedding magnitude, the transmissible fraction of virus. We found that host genes were differentially expressed between LPAIV-infected and uninfected birds early in the infection, host genes were differentially expressed between shed level groups at one-, three-, and five-days post-infection, host gene expression was associated with LPAIV infection patterns over time, and genes of the innate immune system had a positive linear relationship with cloacal viral shedding. This study provides important insights into host gene expression patterns associated with intraspecific LPAIV shedding variation and can serve as a foundation for future studies focused on the identification of host factors that drive or permit the emergence of high viral shedding individuals.

Comparing the potential of Bacillus amyloliquefaciens CGMCC18230 with antimicrobial growth promoters for growth performance, bone development, expression of phosphorus transporters, and excreta microbiome in broiler chickens

Bone health of broiler chickens is essential for welfare and production. In this study, the probiotic Bacillus amyloliquefaciens (BA) CGMCC18230 was compared with antimicrobial growth promoters (AGPs) for its ability to promote growth and bone health. To address this, a total of 180 Arbor Acres (AA) 1-day-old, male, broiler chicks were randomly allocated into 3 treatment groups, with 6 replicates, containing 10 chicks in each replicate. The treatment groups were: control group (CON) fed a corn-soybean based diet; BA treatment group fed the basal diet supplemented with 2.5 × 10¹⁰ CFU/kg BA CGMCC18230; AGPs treatment group was fed the basal diet containing the antibiotics aureomycin (75 mg/kg), flavomycin (5 mg/kg) and kitasamycin (20 mg/kg). Over the 42 d experiment, broilers fed BA and AGPs diets both had higher BW, and the ADG was significantly (P < 0.05) higher than that of the CON group both in the grower phase (22–42 d) and overall. Moreover, with BA birds had higher (P < 0.05) serum concentrations of phosphorus (P, day 42) and alkaline phosphatase (ALP, days 21 and 42). Conversely, the content of P in excreta decreased significantly (P < 0.05) on days 21 and 42. Tibia bone mineralization was improved in BA, and the mRNA of P transport related genes PiT-1,2 in the duodenum and jejunum were significantly up-regulated in the BA group than in the CON group (P < 0.05). 16S rRNA gene sequencing revealed that dietary BA supplementation increased the relative abundance of butyrate-producing bacteria (Ruminococcaceae) and polyamine-producing bacteria (Akkermansia and Alistipes), which had a positive effect on bone development. These data show that dietary supplementation of BA CGMCC18320 improves broiler growth performance and bone health similar to supplementation with AGPs through up-regulation of intestinal P transporters, microbial modulation and increase P retention. However, no significant influence of BA CGMCC18320 supplementation on the retention of Ca was found.

Evaluation of Predisposing Factors of Necrotic Enteritis in Experimentally Challenged Broiler Chickens

Simple Summary

The ban of antibiotic growth promoters in animal feed increased the number of cases of necrotic enteritis (NE) in broilers, greatly affecting the poultry industry. The induction of experimental NE faces challenges, as it is a multifactorial disease and the pathogenesis is not fully understood, hampering the development of in vivo studies for disease control and prevention strategies. The literature reports several protocols using different factors to assist in NE induction. This study assessed predisposing factors, such as immunosuppression, infection or both, by Eimeria spp. in broilers (n = 99) fed a wheat-based diet and challenged with three different strains of Clostridium perfringens (CP). Under microscopy, Eimeria spp. had a negative effect on intestinal morphometry and favored the increase of intraepithelial lymphocytes. However, the macroscopic analysis did not show which factor was more effective in potentiating the lesions, suggesting a synergistic effect between the strain of CP used and the predisposing factors. Therefore, each experimental protocol should first be evaluated for the association of the CP strain with the predisposing factors.

Abstract

Clostridium perfringens is the etiological agent of NE, a disease that greatly affects the poultry industry. Experiments on the induction of NE are difficult to carry out, as it is a multifactorial disease, and thus different predisposing factors have been used. This study evaluated the effect of the Gumboro disease vaccine virus vaccine (IBDV-vac) associated or not with infection by Eimeria spp. in broilers, as a predisposing factor for NE. Broilers (n = 99) were divided into groups (11) challenged with IBDV-vac, Eimeria spp. CP type G (CP13, CP14 and CP03) or both. The macroscopic evaluation revealed that the highest average (3.45) of injury occurred for the CP13 + IBDV-vac group. The microscopic analysis showed that Eimeria spp. increased the population of intraepithelial lymphocytes and reduced the villus/crypt ratio in duodenum and jejunum when associated with CP13 or CP14. There was a synergistic effect between the CP strain used and the predisposing factors; nevertheless, it was not clear which was the most effective predisposing factor to potentiate the lesions, suggesting that the association of the strain with the factors should first be evaluated for each experimental protocol.

Efficacy of clofazimine and nitazoxanide combination in treating intestinal cryptosporidiosis and enhancing intestinal cellular regeneration in immunocompromised mice

Cryptosporidium is a widely distributed food and water-borne enteric protozoan that affects a wide range of vertebrates, resulting in life-threatening consequences, particularly in immunocompromised hosts. The lack of effective anti-cryptosporidial drugs may be related to the parasite's unique intestinal location, plus the lack of studies on the process by which the protozoan is able to impair intestinal cellular function. The present work aimed to assess the effect of clofazimine (CFZ), an FDA-approved drug for the treatment of leprosy, as an anti-cryptosporidial drug, using transmission electron microscopy (TEM) and an immunocompromised mouse model. The affected intestinal mucosa with parasitic stages in the infected non-treated group showed signs of severe cellular degeneration, including the loss of tight junctions, deformed and damaged microvilli and irregularly distributed nuclei with a severely vacuolated cytoplasm. Comparatively, nitazoxanide (NTZ) monotherapy showed the lowest efficacy as the drug was associated with the lowest rate of oocyst shedding. In addition, NTZ treatment failed to achieve the return of complete cellular function; abnormalities were evident in the microvilli, cytoplasmic organelles and nuclear features. Clofazimine demonstrated an improvement of the mucosal cellular components, including mitochondria and significantly reduced oocyst shedding. Combined treatment with low-dose CFZ and half-dose NTZ resulted in a significant improvement in the enterocyte cellular structures with an absence of intracellular parasitic stages. These results indicate that CFZ, a safe and readily prescribed drug, effectively reduces cryptosporidiosis when used in combination with only half the dose of NTZ. Used in combination, these drugs were shown to be efficient in regaining intestinal cellular activity following Cryptosporidium-induced functional damage in an immunocompromised mouse model.

Compound Probiotics Improve Body Growth Performance by Enhancing Intestinal Development of Broilers with Subclinical Necrotic Enteritis

The aim of this study is to explore whether or not the combined application of BS15 and H2 is capable to have a more effective control effect on SNE in broilers. A total of 240 1-day-old female chickens were randomly divided into 5 groups: (a) basal diet in negative control group (NC group); (b) basal diet + SNE infection (coccidiosis vaccine + CP) (PC group); (c) basal diet + SNE infection + H2 pre-treatment (BT group); (d) basal diet + SNE infection + BS15 pre-treatment (LT group); and (e) basal diet + SNE infection + H2 pre-treatment + BS15 pre-treatment (MT group). The results showed the MT group had the most positive effect on inhibiting the negative effect of growth performance at 42 days of age. In the detection of the NC, PC, and MT group indicators at 28 days of age, we found that MT group significantly promoted ileum tissue development of broilers, and the ileum of broilers in the MT group formed a flora structure different from NC and PC, although it was found that the MT group had no effect on the butyrate level in the cecum, but it could affect the serum immune level, such as significantly reducing the level of pro-inflammatory cytokine IL-8 and increasing the content of immunoglobulin IgM and IgG. In conclusion, the composite preparation of Lactobacillus johnsonii BS15 and Bacillus licheniformis H2 could effectively improve the growth performance against SNE broilers, which is possibly caused by the improvement of the immune levels, the reduction of inflammation levels, and the promotion of the intestinal development.

Probiotics and gut health: linking gut homeostasis and poultry productivity

The use of probiotics in poultry production has increased rapidly, and this movement has been promoted by global events, such as the prohibition or decline in the use of antibiotic growth promotants in poultry feeds. There has been a persistent search for alternative feed additives, and probiotics have shown that they can restore the composition of the gut microbiota, and produce health benefits to the host, including improvements in performance. Probiotics have shown potential to increase productivity in poultry, especially in flocks challenged by stressors. However, the outcomes of probiotic use have not always been consistent. There is an increasing demand for well defined products that can be applied strategically, and currently, probiotic research is focusing on delineating their mechanisms of action in the gut that contribute to an improved efficacy. In particular, mechanisms involved in the maintenance and protection of intestinal barrier integrity and the role of the gut microbiota are being extensively investigated. It has been shown that probiotics modulate intestinal immune pathways both directly and through interactions with the gut microbiota. These interactions are key to maintaining gut homeostasis and function, and improving feed efficiency. Research has demonstrated that probiotics execute their effects through multiple mechanisms. The present review describes recent advances in probiotic use in poultry. It focuses on the current understanding of gut homeostasis and gut health in chickens, and how it can be assessed and improved through supplementation of poultry diets with probiotics in poultry diets. In particular, cellular and molecular mechanisms involved in the maintenance and protection of gut barrier structure and function are described. It also highlights important factors that influence probiotic efficacy and bird performance.