Antibiotics in 16-day-old broilers temporarily affect microbial and immune parameters in the gut

Yeast cell wall polysaccharides accelerate yet in-feed antibiotic delays intestinal development and maturation via modulating gut microbiome in chickens

BACKGROUND

It is important to promote intestinal development and maturation of chicks for feed digestion and utilization, intestinal health, and disease resistance. This study aimed to investigate the effects of dietary yeast cell wall polysaccharides (YCWP) addition on intestinal development and maturation of chickens and its potential action mechanism.

METHODS

180 one-day-old male Arbor Acres broilers were randomly assigned to three groups containing control (basal diets without any antibiotics or anticoccidial drug), bacitracin methylene disalicylate (BMD)-treated group (50 mg/kg) and YCWP-supplemented group (100 mg/kg).

RESULTS

Compared with control group, in-feed antibiotic BMD continuous administration significantly decreased crypt depth (d 21) and villus height (d 42) along with mucosal maltase activity (d 42) in the ileum (P < 0.05). Also, BMD markedly downregulated gene expression levels of β-catenin, lysozyme, occludin and FABP-2 (d 21) and innate immune related genes CD83 and MHC-I mRNA levels (d 42, P < 0.05), and decreased goblet cell counts in the ileum of chickens (d 21 and d 42, P < 0.05). While, TLR-2, TLR-6 and iNOS mRNA abundances were notably upregulated by BMD treatment (d 42, P < 0.05). Nevertheless, dietary YCWP addition significantly increased the ratio of villus height to crypt depth (d 21), villus surface area (d 21 and d 42), ileal alkaline phosphatase and maltase activities as well as goblet cell (d 21 and d 42) and IgA-producing plasma cell numbers as compared to BMD treatment (d 21, P < 0.05). YCWP addition also upregulated gene expression levels of Lgr5, Wnt/β-catenin signaling pathway related gene (Wnt3, β-catenin, d 21; β-catenin, d 42), intestinal cells proliferation marker Ki-67 and barrier function related genes (occludin, d 21 and d 42, P < 0.05). Moreover, YCWP significantly increased antigen presenting cell marker related genes (MHC-II, d 21; CD83 and MHC-I, d 42), TLR-1, TLR-2 and TLR-6 mRNA levels (d 21, P < 0.05). Cecal microbiome analysis showed that YCWP addition obviously improved cecal microbial composition, as indicated by increasing relative abundance of Fournierella, Psychrobacter and Ruminiclostridium on d 21, and Alistipes and Lactobacillus on d 42, which were positively related with gut development and maturation related indexes (P < 0.05).

CONCLUSION

Collectively, YCWP promoted yet antibiotic BMD delayed intestinal morphological and immunological development linked with modulating gut microbiome in chickens.

Selection for amoxicillin-, doxycycline-, and enrofloxacin-resistant Escherichia coli at concentrations lower than the ECOFF in broiler-derived cecal fermentations

Antimicrobial resistance (AMR) is an emerging worldwide problem and a health threat for humans and animals. Antimicrobial usage in human and animal medicine or in agriculture results in selection for AMR. The selective concentration of antimicrobial compounds can be lower than the minimum inhibitory concentration and differs between environments, which can be a reason for bacterial resistance. Therefore, knowledge of the minimal selective concentration (MSC), under natural conditions, is essential to understand the selective window of bacteria when exposed to residual antimicrobials. In this study, we estimated the MSCs of three antimicrobials, amoxicillin, doxycycline, and enrofloxacin in a complex microbial community by conducting fermentation assays with cecal material derived from broilers. We examined the phenotypic resistance of Escherichia coli, resistome, and microbiome after 6 and 30 hours of fermenting in the presence of the antimicrobials of interest. The concentrations were estimated to be 10-100 times lower than the epidemiological cut-off values in E. coli for the respective antimicrobials as determined by EUCAST, resulting in an MSC between 0.08 and 0.8 mg/L for amoxicillin, 0.4 and 4 mg/L for doxycycline, and 0.0125 and 0.125 mg/L for enrofloxacin. Additionally, resistome analysis provided an MSC for doxycycline between 0.4 and 4 mg/L, but amoxicillin and enrofloxacin exposure did not induce a significant difference. Our findings indicate at which concentrations there is still selection for antimicrobial-resistant bacteria. This knowledge can be used to manage the risk of the emergence of antimicrobial-resistant bacteria.IMPORTANCEAntimicrobial resistance possibly affects human and animal health, as well as economic prosperity in the future. The rise of antimicrobial-resistant bacteria is a consequence of using antimicrobial compounds in humans and animals selecting for antimicrobial-resistant bacteria. Concentrations reached during treatment are known to be selective for resistant bacteria. However, at which concentrations residues are still selective is important, especially for antimicrobial compounds that remain in the environment at low concentrations. The data in this paper might inform decisions regarding guidelines and regulations for the use of specific antimicrobials. In this study, we are providing these minimal selective concentrations for amoxicillin, doxycycline, and enrofloxacin in complex environments.

Antibiotic Cocktail Effects on Intestinal Microbial Community, Barrier Function, and Immune Function in Early Broiler Chickens

This study investigated the effects of an antibiotic cocktail on intestinal microbial composition, mechanical barrier structure, and immune functions in early broilers. One-day-old healthy male broiler chicks were treated with a broad-spectrum antibiotic cocktail (ABX; neomycin, ampicillin, metronidazole, vancomycin, and kanamycin, 0.5 g/L each) or not in drinking water for 7 and 14 days, respectively. Sequencing of 16S rRNA revealed that ABX treatment significantly reduced relative Firmicutes, unclassified Lachnospiraceae, unclassified Oscillospiraceae, Ruminococcus torques, and unclassified Ruminococcaceae abundance in the cecum and relative Firmicutes, Lactobacillus and Baccillus abundance in the ileum, but significantly increased richness (Chao and ACE indices) and relative Enterococcus abundance in the ileum and cecum along with relatively enriched Bacteroidetes, Proteobacteria, Cyanobacteria, and Enterococcus levels in the ileum following ABX treatment for 14 days. ABX treatment for 14 days also significantly decreased intestinal weight and length, along with villus height (VH) and crypt depth (CD) of the small intestine, and remarkably increased serum LPS, TNF-α, IFN-γ, and IgG levels, as well as intestinal mucosa DAO and MPO activity. Moreover, prolonged use of ABX significantly downregulated occludin, ZO-1, and mucin 2 gene expression, along with goblet cell numbers in the ileum. Additionally, chickens given ABX for 14 days had lower acetic acid, butyric acid, and isobutyric acid content in the cecum than the chickens treated with ABX for 7 days and untreated chickens. Spearman correlation analysis found that those decreased potential beneficial bacteria were positively correlated with gut health-related indices, while those increased potential pathogenic strains were positively correlated with gut inflammation and gut injury-related parameters. Taken together, prolonged ABX application increased antibiotic-resistant species abundance, induced gut microbiota dysbiosis, delayed intestinal morphological development, disrupted intestinal barrier function, and perturbed immune response in early chickens. This study provides a reliable lower-bacteria chicken model for further investigation of the function of certain beneficial bacteria in the gut by fecal microbiota transplantation into germ-free or antibiotic-treated chickens.

Interactions between the helminth and intestinal microbiome in smallholder chicken farming systems

Helminth parasite infections are widespread in smallholder farming systems affecting farmers and livestock animals. There are pathogenic parasites that populate the gut of their host and coexist closely with the gut microbiota. The physical and immunological environment of the gut can be modified by parasites and microbiota creating a wide range of interactions. These interactions modify the development of infection, affects overall host health, and can modify the way a host interacts with its bacterial microbiota. In addition, where there is a high worm burden parasites will affect the health of the host and intestinal tract colonization. This review highlights key studies on the interaction between helminth parasites and the intestinal microbiome to understand the relationship between parasitic worm infections and gut microbiome health in chickens. Finally, the review discusses modulations, molecular changes, and the importance of helminth-microbiome interactions for the host.

Bioactive compounds, antibiotics and heavy metals: effects on the intestinal structure and microbiome of monogastric animals – a non-systematic review

The intestinal structure and gut microbiota are essential for the animals‘ health. Chemical components taken with food provide the right environment for a specific microbiome which, together with its metabolites and the products of digestion, create an environment, which in turn is affects the population size of specific bacteria. Disturbances in the composition of the gut microbiota can be a reason for the malformation of guts, which has a decisive impact on the animal‘ health. This review aimed to analyse scientific literature, published over the past 20 years, concerning the effect of nutritional factors on gut health, determined by the intestinal structure and microbiota of monogastric animals. Several topics have been investigated: bioactive compounds (probiotics, prebiotics, organic acids, and herbal active substances), antibiotics and heavy metals (essentaial minerals and toxic heavy metals).

Recent developments in antimicrobial growth promoters in chicken health: Opportunities and challenges

With a continuously increasing human population is an increasing global demand for food. People in countries with a higher socioeconomic status tend to switch their preferences from grains to meat and high-value foods. Their preference for chicken as a source of protein has grown by 70% over the last three decades. Many studies have shown the role of feed in regulating the animal gut microbiome and its impact on host health. The microbiome absorbs nutrients, digests foods, induces a mucosal immune response, maintains homeostasis, and regulates bioactive metabolites. These metabolic activities are influenced by the microbiota and diet. An imbalance in microbiota affects host physiology and progressively causes disorders and diseases. With the use of antibiotics, a shift from dysbiosis with a higher density of pathogens to homeostasis can occur. However, the progressive use of higher doses of antibiotics proved harmful and resulted in the emergence of multidrug-resistant microbes. As a result, the use of antibiotics as feed additives has been banned. Researchers, regulatory authorities, and managers in the poultry industry have assessed the challenges associated with these restrictions. Research has sought to identify alternatives to antibiotic growth promoters for poultry that do not have any adverse effects. Modulating the host intestinal microbiome by regulating dietary factors is much easier than manipulating host genetics. Research efforts have led to the identification of feed additives, including bacteriocins, immunostimulants, organic acids, phytogenics, prebiotics, probiotics, phytoncides, and bacteriophages. In contrast to focusing on one or more of these alternative bioadditives, an improved feed conversion ratio with enhanced poultry products is possible by employing a combination of feed additives. This article may be helpful in future research towards developing a sustainable poultry industry through the use of the proposed alternatives.

Immune Parameters in Chickens Treated with Antibiotics and Probiotics during Early Life

The aim of the study was to compare the effect of the administration of antibiotics or probiotics on chickens in their first week of life, on selected parameters of humoral and cellular immunity, and on the bursa of Fabricius and spleen indices. The experiment was carried out on 90 one-day-old male broilers. The control group received no additive in the drinking water; the group GP received a probiotic providing Enterococcus faecium and Bacillus amyloliquefaciens; and the group GA received 10% enrofloxacin in the drinking water on the first five days of life. Administration of the antibiotic enrofloxacin or a probiotic containing E. faecium and B. amyloliquefaciens strains to chickens in their first week of life exerts pronounced immunomodulatory effects on humoral and cellular defense mechanisms in these birds. The changes in the subpopulations of B and T cells immediately following early administration of enrofloxacin or the probiotic were not observed at the age of 35 days. Early administration of enrofloxacin can pose a risk of suppression of humoral immunity, as indicated by the significant decrease in the total IgY concentration in the plasma of the chickens.

Effect of Antibiotics on the Colonization of Live Attenuated Salmonella Enteritidis Vaccine in Chickens

Salmonellosis, caused by Salmonella Enteritidis, is a prevalent zoonosis that has serious consequences for human health and the development of the poultry sector. The Salmonella Enteritis live vaccine (Sm24/Rif12/Ssq strain) is used to prevent Salmonella Enteritidis around the world. However, in some parts of the world, poultry flocks are frequently raised under intensive conditions, with significant amounts of antimicrobials to prevent and treat disease and to promote growth. To investigate whether antibiotic use influences the colonization of orally administered Salmonella live vaccines, 240 1-day-old specific pathogen-free chicks were randomly divided into 24 groups of 10 animals for this study. The different groups were treated with different antibiotics, which included ceftiofur, amoxicillin, enrofloxacin, and lincomycin–spectinomycin. Each group was immunized 2, 3, 4, and 5 days after withdrawal, respectively. At 5 days after immunization, the blood, liver, and ceca with contents were collected for the isolation of the Salmonella live vaccine strain. The result showed that no Salmonella vaccine strain was isolated in the blood and liver of the chicks in those groups. The highest number of Salmonella vaccine strains was isolated in the cecum from chicks vaccinated 2 days after ceftiofur withdrawal, and no Salmonella vaccine strain was isolated from the cecum in chicks immunized 3 days after ceftiofur withdrawal. Among the chickens immunized 4 days after the withdrawal of amoxicillin, enrofloxacin, and lincomycin–spectinomycin, the number of Salmonella vaccine colonization in the cecum was the highest, which was higher than that of the chickens immunized at other withdrawal interval (2, 3, and 5 days) groups and was higher than that of the chickens without treatment (P < 0.05). This study provides a reference for the effective use of the Salmonella Enteritidis live vaccine and key antibiotics commonly utilized in the poultry industry.

Impact of Antibiotic Therapies on Resistance Genes Dynamic and Composition of the Animal Gut Microbiota

Antibiotics are major disruptors of the gastrointestinal microbiota, depleting bacterial species beneficial for the host health and favoring the emergence of potential pathogens. Furthermore, the intestine is a reactor of antibiotic resistance emergence, and the presence of antibiotics exacerbates the selection of resistant bacteria that can disseminate in the environment and propagate to further hosts. We reviewed studies analyzing the effect of antibiotics on the intestinal microbiota and antibiotic resistance conducted on animals, focusing on the main food-producing and companion animals. Irrespective of antibiotic classes and animal hosts, therapeutic dosage decreased species diversity and richness favoring the bloom of potential enteropathogens and the selection of antibiotic resistance. These negative effects of antibiotic therapies seem ineluctable but often were mitigated when an antibiotic was administered by parenteral route. Sub-therapeutic dosages caused the augmentation of taxa involved in sugar metabolism, suggesting a link with weight gain. This result should not be interpreted positively, considering that parallel information on antibiotic resistance selection was rarely reported and selection of antibiotic resistance is known to occur also at low antibiotic concentration. However, studies on the effect of antibiotics as growth promoters put the basis for understanding the gut microbiota composition and function in this situation. This knowledge could inspire alternative strategies to antibiotics, such as probiotics, for improving animal performance. This review encompasses the analysis of the main animal hosts and all antibiotic classes, and highlights the future challenges and gaps of knowledge that should be filled. Further studies are necessary for elucidating pharmacodynamics in animals in order to improve therapy duration, antibiotic dosages, and administration routes for mitigating negative effects of antibiotic therapies. Furthermore, this review highlights that studies on aminoglycosides are almost inexistent, and they should be increased, considering that aminoglycosides are the first most commonly used antibiotic family in companion animals. Harmonization of experimental procedures is necessary in this research field. In fact, current studies are based on different experimental set-up varying for antibiotic dosage, regimen, administration, and downstream microbiota analysis. In the future, shotgun metagenomics coupled with long-reads sequencing should become a standard experimental approach enabling to gather comprehensive knowledge on GIM in terms of composition and taxonomic functions, and of ARGs. Decorticating GIM in animals will unveil revolutionary strategies for medication and improvement of animals' health status, with positive consequences on global health.

Maximum levels of cross-contamination for 24 antimicrobial active substances in non-target feed. Part 4: β-Lactams: amoxicillin and penicillin V

The specific concentrations of amoxicillin and penicillin V in non-target feed for food-producing animals, below which there would not be an effect on the emergence of, and/or selection for, resistance in bacteria relevant for human and animal health, as well as the specific antimicrobial concentrations in feed which have an effect in terms of growth promotion/increased yield were assessed by EFSA in collaboration with EMA. Details of the methodology used for this assessment, associated data gaps and uncertainties, are presented in a separate document. To address antimicrobial resistance, the Feed Antimicrobial Resistance Selection Concentration (FARSC) model developed specifically for the assessment was applied. However, due to the lack of data on the parameters required to calculate the FARSC, it was not possible to conclude the assessment until further experimental data become available. To address growth promotion, data from scientific publications obtained from an extensive literature review were used. Levels in feed that showed to have an effect on growth promotion/increased yield were reported for amoxicillin, whilst for penicillin V no suitable data for the assessment were available. It was recommended to carry out studies to generate the data that are required to fill the gaps which prevented the calculation of the FARSC for these two antimicrobials.

Immunosecurity: immunomodulants enhance immune responses in chickens

The global population has increased with swift urbanization in developing countries, and it is likely to result in a high demand for animal-derived protein-rich foods. Animal farming has been constantly affected by various stressful conditions, which can be categorized into physical, environmental, nutritional, and biological factors. Such conditions could be exacerbated by banning on the use of antibiotics as a growth promoter together with a pandemic situation including, but not limited to, African swine fever, avian influenza, and foot-and-mouth disease. To alleviate these pervasive tension, various immunomodulants have been suggested as alternatives for antibiotics. Various studies have investigated how stressors (i.e., imbalanced nutrition, dysbiosis, and disease) could negatively affect nutritional physiology in chickens. Importantly, the immune system is critical for host protective activity against pathogens, but at the same time excessive immune responses negatively affect its productivity. Yet, comprehensive review articles addressing the impact of such stress factors on the immune system of chickens are scarce. In this review, we categorize these stressors and their effects on the immune system of chickens and attempt to provide immunomodulants which can be a solution to the aforementioned problems facing the chicken industry.

The effect of different combinations of antibiotic cocktails on mice and selection of animal models for further microbiota research

The gut microbiota is closely related to host health and disease. However, there are no suitable animal models available at present for exploring its functions. We analyzed the effect of 3 different antibiotic cocktails (ABx) via two administration routes on the composition of murine gut microbiota, as well as on the general physiological and metabolic indices. High-throughput 16S rRNA sequencing showed that ABx treatment altered the gut microbiota community structure, and also caused low-degree inflammation in the colon. In addition, ad libitum administration of antibiotics depleted the gut microbiota more effectively compared to direct oral gavage, especially with 3ABx. The ABx treatment also had a significant impact on renal and liver functions, as indicated by the altered serum levels of creatinine, urea, total triglycerides, and total cholesterol. Finally, Spearman's correlation analysis showed that the predominant bacterial genera resulting from ABx intervention, including Lactobacillus, Roseburia, and Candidatus-Saccharimonas, were negatively correlated with renal function indices. Taken together, different antibiotic combinations and interventions deplete the gut microbiota and induce physiological changes in the host. Our findings provide the basis for developing an adaptive animal model for studying gut microbiota. KEY POINTS: • Ad libitum administration of 3ABx can effectively deplete intestinal microbiota. • ABx treatment may have slight effect on renal and liver function. • The levels of urea and creatinine correlated with the growth of Roseburia.

Different effects of probiotics and antibiotics on the composition of microbiota, SCFAs concentrations and FFAR2/3 mRNA expression in broiler chickens

AIMS

The aims of this study were to investigate the effects of probiotics and antibiotics on microbial composition, short chain fatty acids (SCFAs) concentration and free fatty acid receptor 2/3 (FFAR2/3) expression in boiler chickens.

METHODS AND RESULTS

A total of 150 1-day-old male broilers were randomly allocated into three groups, control (CON) group, probiotics (PB) group and antibiotics (ATB) group. Results indicated that PB improved the average body weight from 1 to 21 days and feed intake from 21 to 42 days (P < 0·05), while ATB improved the feed efficiency from 1 to 42 days (P < 0·05). Based on 16s rRNA sequencing, PB treatment increased the amount of kingdom bacteria, and the relative abundance of the main bacteria including acetate and butyrate producing bacteria of phylum Firmicutes, family Ruminococcaceae and genus Faecalibacterium. ATB treatment also increased the relative abundance of phylum Firmicutes, family Ruminococcaceae and Lachnospiraceae, however, it introduced some pathogenic bacteria, such as bacteria of family Rikenellaceae and Enterobacteriaceae. Gas chromatography and mass spectrometry (GC-MS) assay revealed that PB increased acetate and butyrate concentrations at both 21 and 42 days, and propionate at 42 days in the colorectum. Moreover qRT-PCR analysis showed PB treatment significantly activated the FFAR2/3 mRNA expressions. On the contrast, ATB treatment lowered the colorectal propionate at 21 days, and decreased acetate, propionate and butyrate concentrations at 42 days, accompanied with decreased FFAR2/3 mRNA expressions.

CONCLUSIONS

Compared to the CON birds, an enriched SCFAs producing bacteria with higher SCFAs contents and activated FFAR2/3 expressions are prominent features of PB birds. However, antibiotics treatment plays the reverse effect compared to PB treatment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study brings a significant idea that less SCFAs concentration may be another reason why the antibiotics inhibit the immune system development and immunity of the body.

Effect of antibiotic treatment on microbial composition and expression of antimicrobial peptides and cytokines in the chick cecum

The aim of this study was to confirm whether the expression of innate immune molecules in the chick cecum is altered in association with changes in the composition of the intestinal microbiome that are regulated by treatment with antibiotics. Broiler chicks were administered with antibiotics (penicillin and streptomycin) daily, and the composition of the microbiota, expression of innate immune molecules, and localization of antimicrobial peptides in the chick cecum were examined at day 7 and day 14 using real-time PCR and immunohistochemistry. The oral administration of antibiotics caused an increase in the relative frequency of the Enterobacteriaceae family and a decrease in some gram-negative (Barnesiellaceae) and gram-positive bacterial (Clostridiaceae and Erysipelotrichaceae) families. The gene expression levels of immune molecules, including 4 Toll-like receptors (TLR) (TLR 2, 4, 5, and 21), inflammation-related cytokines (IL-1β, TGFβ3, TGFβ4, and IL-8), and antimicrobial peptides (avian β-defensins and cathelicidins) showed a tendency to decrease with antibiotic treatment at day 7. However, expression levels of TLR21 and some cytokines (IL-1β, TGFβ3, and IL-8) were higher in the cecum or cecal tonsils of the antibiotic-treated group than in those of the control at day 14. The immunoreactive avian β-defensin 2 and cathelicidin 1 proteins were localized in the leukocyte-like cells in the lamina propria, and they were aggregated in the form of small islands. We conclude that the expression of innate immune molecules, including TLR, inflammation-related cytokines, and antimicrobial peptides, in the cecum are altered in association with changes in the density or composition of the luminal microbiota during the early phase of life in chicks.

The Microbial Pecking Order: Utilization of Intestinal Microbiota for Poultry Health

The loss of antibiotics as a tool to improve feed efficiency in poultry production has increased the urgency to understand how the microbiota interacts with animals to impact productivity and health. Modulating and harnessing microbiota-host interactions is a promising way to promote poultry health and production efficiencies without antibiotics. In poultry, the microbiome is influenced by many host and external factors including host species, age, gut compartment, diet, and environmental exposure to microbes. Because so many factors contribute to the microbiota composition, specific knowledge is needed to predict how the microbiome will respond to interventions. The effects of antibiotics on microbiomes have been well documented, with different classes of antibiotics having distinctive, specific outcomes on bacterial functions and membership. Non-antibiotic interventions, such as probiotics and prebiotics, target specific bacterial taxa or function to enhance beneficial properties of microbes in the gut. Beneficial bacteria provide a benefit by displacing pathogens and/or producing metabolites (e.g., short chain fatty acids or tryptophan metabolites) that promote poultry health by improving mucosal barrier function or immune function. Microbiota modulation has been used as a tool to reduce pathogen carriage, improve growth, and modulate the immune system. An increased understanding of how the microbiota interacts with animal hosts will improve microbiome intervention strategies to mitigate production losses without the need for antibiotics.

Antibiotic-Induced Disruption of Gut Microbiota Alters Local Metabolomes and Immune Responses

Gut microbiome plays an essential role in modulating host immune responses. However, little is known about the interaction of microbiota, their metabolites and relevant inflammatory responses in the gut. By treating the mice with three different antibiotics (enrofloxacin, vancomycin, and polymixin B sulfate), we aimed to investigate the effects of different antibiotics exposure on gut microbiota, microbial metabolism, inflammation responses in the gut, and most importantly, pinpoint the underlying interactions between them. Although the administration of different antibiotics can lead to different effects on mouse models, the treatment did not affect the average body weight of the mice. A heavier caecum was observed in vancomycin treated mice. Treatment by these three antibiotics significantly up-regulated gene expression of various cytokines in the colon. Enrofloxacin treated mice seemed to have an increased Th1 response in the colon. However, such a difference was not found in mice treated by vancomycin or polymixin B sulfate. Vancomycin treatment induced significant changes in bacterial composition at phylum and family level and decreased richness and diversity at species level. Enrofloxacin treatment only induced changes in composition at family presenting as an increase in Prevotellaceae and Rikenellaceae and a decrease in Bacteroidaceae. However, no significant difference was observed after polymixin B sulfate treatment. When compared with the control group, significant metabolic shift was found in the enrofloxacin and vancomycin treated group. The metabolic changes mainly occurred in Valine, leucine, and isoleucine biosynthesis pathway and beta-Alanine metabolism in enrofloxacin treated group. For vancomycin treatment metabolic changes were mainly found in beta-Alanine metabolism and Alanine, aspartate and glutamate metabolism pathway. Moreover, modifications observed in the microbiota compositions were correlated with the metabolite concentrations. For example, concentration of pentadecanoic acid was positively correlated with richness of Rikenellaceae and Prevotellaceae and negatively correlated with Enterobacteriaceae. This study suggests that the antibiotic-induced changes in gut microbiota might contribute to the inflammation responses through the alternation of metabolic status, providing a novel insight regarding a complex network that integrates the different interactions between gut microbiota, metabolic functions, and immune responses in host.

Strategies to modulate the intestinal microbiota and their effects on nutrient utilization, performance, and health of poultry

Poultry is widely produced and consumed meat globally. Its demand is expected to continue increasing to meet the animal protein requirement for ever-increasing human population. Thus, the challenge that poultry scientists and industry face are to produce sufficient amount of poultry meat in the most efficient way. In the past, using antibiotics to promote the growth of poultry and manage gut microbiota was a norm. However, due to concerns over potential fatalistic impacts on food animals and indirectly to humans, their use as feed additives are banned or regulated in several jurisdictions. In this changed context, several alternative strategies have been proposed with some success that mimics the functions of antibiotics as growth promoters and modulate gut microbiota for their beneficial roles. These include the use of probiotics, prebiotics, organic acids, and exogenous enzyme, among others. Gut microbiota and their metabolic products improve nutrient digestion, absorption, metabolism, and overall health and growth performance of poultry. This paper reviews the available information on the effect of feed additives used to modulate intestinal microbiota of poultry and their effects on overall health and growth performance. Understanding these functions and interactions will help to develop new dietary and managerial strategies that will ultimately lead to enhanced feed utilization and improved growth performance of poultry. This review will help future researchers and industry to identify alternative feed ingredients having properties like prebiotics, probiotics, organic acids, and exogenous enzymes.