Ameliorative avian gut environment and bird productivity through the application of safe antibiotics alternatives: a comprehensive review

The avian digestive tract is an important system for converting ingested food into the nutrients their bodies need for maintenance, growth, and reproduction (meat, table eggs, and fertile eggs). Therefore, preserving digestive system integrity is crucial to bird health and productivity. As an alternative to antibiotics, the world has recently turned to the use of natural products to enhance avian development, intestinal health, and production. Therefore, the primary goal of this review is to explain the various characteristics of the avian digestive tract and how to enhance its performance with natural, safe feed additives such as exogenous enzymes, organic acids, photogenic products, amino acids, prebiotics, probiotics, synbiotics, and herbal extracts. In conclusion, the composition of the gut microbiome can be influenced by a number of circumstances, and this has important consequences for the health and productivity of birds. To better understand the connection between pathogens, the variety of therapies available, and the microbiome of the gut, additional research needs to be carried out.

Propionibacteria as promising tools for the production of pro-bioactive scotta: a proof-of-concept study

Dairy propionibacteria are Gram positive Actinomycetota, routinely utilized as starters in Swiss type cheese making and highly appreciated for their probiotic properties and health promoting effects. In this work, within the frame of a circular economy approach, 47 Propionibacterium and Acidipropionibacterium spp. were isolated from goat cheese and milk, and ewe rumen liquor, and characterized in view of their possible utilization for the production of novel pro-bioactive food and feed on scotta, a lactose rich substrate and one of the main by-products of the dairy industry. The evaluation of the Minimum Inhibitory Concentration (MIC) of 13 among the most common antibiotics in clinical practice revealed a general susceptibility to ampicillin, gentamycin, streptomycin, vancomycin, chloramphenicol, and clindamycin while confirming a lower susceptibility to aminoglycosides and ciprofloxacin. Twenty-five isolates, that proved capable of lactose utilization as the sole carbon source, were then characterized for functional and biotechnological properties. Four of them, ascribed to Propionibacterium freudenreichii species, and harboring resistance to bile salts (growth at 0.7-1.56 mM of unconjugated bile salts), acid stress (>80% survival after 1 h at pH 2), osmostress (growth at up to 6.5% NaCl) and lyophilization (survival rate > 80%), were selected and inoculated in scotta. On this substrate the four isolates reached cell densities ranging from 8.11 ± 0.14 to 9.45 ± 0.06 Log CFU mL-1 and proved capable of producing different vitamin B9 vitamers after 72 h incubation at 30°C. In addition, the semi-quantitative analysis following the metabolomics profiling revealed a total production of cobalamin derivatives (vitamin B12) in the range 0.49-1.31 mg L-1, thus suggesting a full activity of the corresponding biosynthetic pathways, likely involving a complex interplay between folate cycle and methylation cycle required in vitamin B12 biosynthesis. These isolates appear interesting candidates for further ad-hoc investigation regarding the production of pro-bioactive scotta.

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.

An updated review on probiotics as an alternative of antibiotics in poultry - A review

Antibiotics used to be supplemented to animal feeds as growth promoter and as an effective strategy to reduce the burden of pathogenic bacteria present in the gastro-intestinal tract. However, in-feed antibiotics also kill bacteria that may be beneficial to the animal. Secondly, unrestricted use of antibiotics enhanced the antibiotic resistance in pathogenic bacteria. To overcome above problems, scientists are taking a great deal of measures to develop alternatives of antibiotics. There is convincing evidence that probiotics could replace in-feed antibiotics in poultry production. Because they have beneficial effects on growth performance, meat quality, bone health and eggshell quality in poultry. Better immune responses, healthier intestinal microflora and morphology which help the birds to resist against disease attack were also identified with the supplementation of probiotics. Probiotics establish cross-feeding between different bacterial strains of gut ecosystem and reduce the blood cholesterol level via bile salt hydrolase activity. The action mode of probiotics was also updated according to recently published literatures, i.e antimicrobial substances generation or toxin reduction. This comprehensive review of probiotics is aimed to highlight the beneficial effects of probiotics as a potential alternative strategy to replace the antibiotics in poultry.

Productive performance, fertility and hatchability, blood indices and gut microbial load in laying quails as affected by two types of probiotic bacteria

This study investigated two kinds of probiotic bacteria (Bacillus toyonensis, B1 and Bifidobacterium bifidum, B2) on laying Japanese quail’s performance, egg quality, fertility and hatchability, blood biochemical characteristics and microbiological parameters. A total of 270 mature quails (180 females and 90 males) were distributed into ten groups in a completely randomized design at eight weeks of age. The experimental groups were as follows: T1: basal diet only (control); T2-T5, basal diet plus 0.05, 0.075, 0.10 and 0.125% B1, respectively; T6: basal diet plus 0.10% B2; T7-T10: basal diet plus 0.05, 0.075, 0.10 and 0.125% B1 plus 0.05% B2, respectively. Results revealed that egg number (EN) and egg weight (EW) were gradually increased (P < 0.01) as the levels of both probiotic types increased. The feed conversion ratio (FCR) was significantly (P < 0.05) better within the total experimental period (8–20 weeks) due to B1 alone or/with B2 supplementation. Values of yolk percentage (Y%) were statistically (P < 0.01) higher only at 8–20 weeks of age and T10 recorded the highest value. By increasing the level of probiotics, fertility and hatchability percentages (F% and H%) were gradually increased (P < 0.01 and P < 0.05). Creatinine (CR) level was statistically reduced in birds fed T4 diet. Also, urea-N and aspartate aminotransferase (AST) levels were reduced in treated birds. The opposite was found regarding alkaline phosphatase (ALP). Conclusively, using B1 and B2 enhanced the productive performance, some egg quality traits, fertility and hatchability, digestive enzyme activities, and reduced the harmful bacteria in the gut of laying Japanese quail. Our findings could recommend to apply T4 (basal diet + 0.10 % B1), T6 (basal diet + 0.10% B2) and T9 (basal diet + 0.10% B1 + 0.05% B2) levels for the best results.

Lactic Acid Bacteria - A Promising Tool for Controlling Chicken Campylobacter Infection

Since 2005, campylobacteriosis has been the most common zoonotic disease in Europe. The main reservoir of pathogenic Campylobacter strains is broilers, which makes raw and undercooked poultry meat two major sources of disease. Infection in chicken flocks is most often asymptomatic, despite a high level of colonization reaching 106-109cfu/g in animal ceca. It is widely believed that controlling the level of colonization of the birds' digestive tract by pathogenic strains is a good way to increase food safety. Many treatments have been proposed to combat or at least reduce the level of colonization in animals reservoirs: probiotics, bacteriophages, vaccines, and anti-Campylobacter bacteriocins. This review focuses on the effects of Campylobacter infection on the chicken microbiome and colonization control strategies using probiotics (mostly lactic acid bacteria, LAB), which are live microorganisms included in the diet of animals as feed additives or supplements. Probiotics are not only an alternative to antibiotics, which were used for years as animal growth promoters, but they also constitute an effective protective barrier against excessive colonization of the digestive system by pathogenic bacteria, including Campylobacter. Moreover, one of the many beneficial functions of probiotics is the ability to manipulate the host's microbiota. Recently, there have also been some promising attempts to use lactic acid bacteria as a delivery system of oral vaccine against Campylobacter. Recombinant LAB strains induce primarily a mucosal immune response against foreign antigens, accompanied by at most a low-level immune response against carrier strains. Since the main barrier against the invasion of pathogens in the gastrointestinal tract is the intestinal mucosal membrane, the development of effective oral vaccines to protect animals against enteric infection is very reasonable.

Probiotic biomarkers and models upside down: From humans to animals

Probiotics development for animal farming implies thorough testing of a vast variety of properties, including adhesion, toxicity, host cells signaling modulation, and immune effects. Being diverse, these properties are often tested individually and using separate biological models, with great emphasis on the host organism. Although being precise, this approach is cost-ineffective, limits the probiotics screening throughput and lacks informativeness due to the 'one model - one test - one property' principle. There is а solution coming from human-derived cells and in vitro systems, an extraordinary example of human models serving animal research. In the present review, we focus on the current outlooks of employing human-derived in vitro biological models in probiotics development for animal applications, examples of such studies and the analysis of concordance between these models and host-derived in vivo data. In our opinion, human-cells derived screening systems allow to test several probiotic properties at once with reasonable precision, great informativeness and less expenses and labor effort.

Protection of the intestinal epithelium of poultry against deleterious effects of dietary lectins by a multi-strain bacterial supplement

The intake of antinutritional factors produce impairment on the intestinal digestive function, impeding the efficient use of nutrients. Probiotics could be useful in poultry breeding to prevent negative effects of antinutritional factors, like the dietary lectins soybean agglutinin (SBA) and wheat germ agglutinin (WGA). Therefore, this investigation aimed to verify that SBA and wheat, which contains WGA, exert harmful effects on the intestinal mucosa and the digestive system of young poultry, and determine if the administration of probiotics able to capture lectins could counteract their effects. The trials performed demonstrated that a mixture of Bifidobacterium infantis CRL 1395, Enterococcus faecium LET 301, Lactobacillus salivarius LET 201, L. reuteri LET 210, and Propionibacterium acidipropionici LET 103, strains with ex vivo ability to interfere with the interaction of lectins and epithelial cells, has no negative effect on young chickens health. Middle levels of SBA, as well as wheat as a source of WGA, resulted in lower activities of intestinal and brush border enzymes and alterations in the integrity and morphological parameters of the chicks jejunal mucosa. The bacteria blend increased the activity of several digestive enzymes and the intestinal maturation marker alkaline phosphatase in birds fed with a conventional diet. Besides, it partially countered the deleterious effects of increased content of SBA, as well as the negative effect of a dietary source of WGA, on digestive enzymes activity and intestinal mucosa integrity. The results highlight the capability of multifunctional bacterial mixtures to protect the digestive system of avian against residual dietary lectins.

Identification of Plant Soot as Novel Safe Feed Additive: Evaluation of 90-Day Oral Toxicity and Prenatal Developmental Toxicity in Rats

Plant soot, as a novel feed additive, could not only improve digestive function but also adsorb mycotoxins and inhibit bacterial infections. The subchronic toxicity and prenatal developmental effects of plant soot were studied for the first time. Our results indicated that there was no subchronic toxicity in the range of 2,000–50,000 mg/kg plant soot added in the feed, and there was no significant difference in reproductive function, embryo development, and teratogenicity between the pregnant rats exposed to 312.5, 1,250, and 5,000 mg/kg plant soot and the control group. The maximum no-observed effect level (NOEL) of supplemental dosage in feed could be set to 50,000 mg/kg, and the maximum intragastric NOEL could be set to 5,000 mg/kg, which preliminarily provided guidance on daily additive amount or clinical protocols for plant soot, as well as promoting the development and application of this harmless antibiotic substitutes.

Probiotics (Direct-Fed Microbials) in Poultry Nutrition and Their Effects on Nutrient Utilization, Growth and Laying Performance, and Gut Health: A Systematic Review

Simple Summary

Probiotics are live bacteria, fungi, or yeasts that supplement the gastrointestinal flora and help to maintain a healthy digestive system, thereby promoting the growth performance and overall health of poultry. Probiotics are increasingly being included in poultry diets as an alternative to antibiotics. This systematic review provides a summary of the use of probiotics in poultry production and the potential role of probiotics in the nutrient utilization, growth and laying performance, and gut health of poultry.

Abstract

Probiotics are live microorganisms which, when administered in adequate amounts, confer health benefits to the host. The use of probiotics in poultry has increased steadily over the years due to higher demand for antibiotic-free poultry. The objective of this systematic review is to present and evaluate the effects of probiotics on the nutrient utilization, growth and laying performance, gut histomorphology, immunity, and gut microbiota of poultry. An electronic search was conducted using relevant keywords to include papers pertinent to the topic. Seventeen commonly used probiotic species were critically assessed for their roles in the performance and gut health of poultry under existing commercial production conditions. The results showed that probiotic supplementation could have the following effects: (1) modification of the intestinal microbiota, (2) stimulation of the immune system, (3) reduction in inflammatory reactions, (4) prevention of pathogen colonization, (5) enhancement of growth performance, (6) alteration of the ileal digestibility and total tract apparent digestibility coefficient, and (7) decrease in ammonia and urea excretion. Thus, probiotics can serve as a potential alternative to antibiotic growth promoters in poultry production. However, factors such as the intestinal health condition of birds, the probiotic inclusion level; and the incubation conditions, feedstuff, and water quality offered to birds may affect the outcome. This systematic review provides a summary of the use of probiotics in poultry production, as well as the potential role of probiotics in the nutrient utilization, growth and laying performance, and gut health of poultry.

Research Note: Effect of butyric acid glycerol esters on ileal and cecal mucosal and luminal microbiota in chickens challenged with Eimeria maxima

Coccidiosis is one of the most prevalent diseases seen in the poultry industry leading to excessive economic losses. The aim of this study was to investigate the effect of butyric acid glycerol esters (BE) on the ileal and cecal microbiota in birds challenged with Eimeria maxima (EM). Ross 708 male broilers were fed a diet supplemented with 0 (control) or 0.25% BE from day 1. On day 21, half of the birds were infected with 10³ EM oocysts. For determing microbiota, ileal and cecal contents and epithelial scrapings were collected at 7 and 10 D postinfection (PI). Alpha diversity of bacterial communities was mostly affected (P < 0.05) by time PI and EM infection. The richness of luminal bacterial populations in the ileum and ceca was affected (P < 0.05) by addition of BE and by time PI × EM × BE interaction, respectively. In the ileal and cecal luminal and mucosal bacterial communities, permutational multivariate analysis of variance (PERMANOVA, unweighted UniFrac) showed significant (P < 0.05) differences because of time PI and interaction between time PI, EM, and BE. Significant (P < 0.05) differences in taxonomic composition at the family level were observed in microbiota of luminal and mucosal populations of the ileum and ceca owing to time PI, EM, BE, and their interactions. The bacterial community present in the cecal lumen was characterized by the lowest number of differential bacteria, whereas the cecal mucosal community was characterized by the highest number of differentially abundant bacteria. In conclusion, our results show that EM infection and time PI has the biggest impact on microbial diversity in the chicken gut. The presence of BE in the diet had a limited effect on gut microbiota.

The association between microbial community and ileal gene expression on intestinal wall thickness alterations in chickens

The dynamic development of the animal intestine with a concurrent succession of microbiota and changes in microbial community and metabolite spectrum can exert far-reaching effects on host physiology. However, the precise mechanism of mutual response between microbiota and the gut is yet to be fully elucidated. Broilers with varying developmental degrees of intestinal wall thickness were selected, and they were divided into the thick group (H type) and the thin group (B type), using multiomics data integration analysis to reveal the fundamental regulatory mechanisms of gut–microbiota interplay. Our data showed, in broilers with similar body weight, the intestinal morphological parameters were improved in H type and the diversity of microbial communities is distinguishable from each other. The beneficial bacteria such as Bifidobacterium breve was increased whereas avian endogenous retrovirus EAV-HP was decreased in the H type compared with the B type. Furthermore, microbial metabolic potentials were more active, especially the biosynthesis of folate was improved in the H type. Similarly, the consolidation of absorption, immunity, metabolism, and development was noticed in the thick group. Correlation analysis indicated that the expression levels of material transport and immunomodulatory-related genes were positively correlated with the relative abundance of several probiotics such as B. breve, Lactobacillus saerimneri, and Butyricicoccus pullicaecorum. Our findings suggest that the chickens with well-developed ileal thickness own exclusive microbial composition and metabolic potential, which is closely related to small intestinal morphogenesis and homeostasis.

Could probiotics be the panacea alternative to the use of antimicrobials in livestock diets?

Probiotics are most frequently derived from the natural microbiota of healthy animals. These bacteria and their metabolic products are viewed as nutritional tools for promoting animal health and productivity, disease prevention and therapy, and food safety in an era defined by increasingly widespread antimicrobial resistance in bacterial pathogens. In contemporary livestock production, antimicrobial usage is indispensable for animal welfare, and employed to enhance growth and feed efficiency. Given the importance of antimicrobials in both human and veterinary medicine, their effective replacement with direct-fed microbials or probiotics could help reduce antimicrobial use, perhaps restoring or extending the usefulness of these precious drugs against serious infections. Thus, probiotic research in livestock is rapidly evolving, aspiring to produce local and systemic health benefits on par with antimicrobials. Although many studies have clearly demonstrated the potential of probiotics to positively affect animal health and inhibit pathogens, experimental evidence suggests that probiotics' successes are modest, conditional, strain-dependent, and transient. Here, we explore current understanding, trends, and emerging applications of probiotic research and usage in major livestock species, and highlight successes in animal health and performance.

Dissect the mode of action of probiotics in affecting host-microbial interactions and immunity in food producing animals

Prophylactic antimicrobials have been widely used in food animal production with the aim to prevent infectious diseases, enhance feed efficiency, and promote growth. However, the extensive use of antimicrobials in food animal production systems has led to the emergence of antimicrobial resistant pathogens, which are potential threats to human and animal health. Probiotics have been proposed to be a promising alternative of prophylactic antimicrobials, with potential beneficial effects on the host animal by improving the balance of intestinal microbiota and host immunity. Although an increasing body of evidence shows that probiotics could directly or indirectly affect gut microbiota and host immune functions, the lack of the understanding of how probiotics influence host-microbial interaction and immunity is one of the reasons for controversial findings from many animal trials, especially in food production animals. Therefore, in this review we focused on the most recent (last ten years) studies on how gut microbiota and host immune function changes in response to probiotics in food production animals (swine, poultry, and ruminant). In addition, the relationship between microbial changes and host immune function was illustrated, and how such relationship differs among animal species was further compared. Moreover, the future directions concerning the mechanisms of how probiotics modulate host-microbial interactions and host immunity were highlighted, which may assist in the optimal supplementation strategy to maximize the efficacy of probiotics to improve animal gut health and productivity.

Dairy Propionibacteria: Versatile Probiotics

Dairy propionibacteria are used as cheese ripening starters, as biopreservative and as beneficial additives, in the food industry. The main species, Propionibacterium freudenreichii, is known as GRAS (Generally Recognized As Safe, USA, FDA). In addition to another dairy species, Propionibacterium acidipropionici, they are included in QPS (Qualified Presumption of Safety) list. Additional to their well-known technological application, dairy propionibacteria increasingly attract attention for their promising probiotic properties. The purpose of this review is to summarize the probiotic characteristics of dairy propionibacteria reported by the updated literature. Indeed, they meet the selection criteria for probiotic bacteria, such as the ability to endure digestive stressing conditions and to adhere to intestinal epithelial cells. This is a prerequisite to bacterial persistence within the gut. The reported beneficial effects are ranked according to property’s type: microbiota modulation, immunomodulation, and cancer modulation. The proposed molecular mechanisms are discussed. Dairy propionibacteria are described as producers of nutraceuticals and beneficial metabolites that are responsible for their versatile probiotic attributes include short chain fatty acids (SCFAs), conjugated fatty acids, surface proteins, and 1,4-dihydroxy-2-naphtoic acid (DHNA). These metabolites possess beneficial properties and their production depends on the strain and on the growth medium. The choice of the fermented food matrix may thus determine the probiotic properties of the ingested product. This review approaches dairy propionibacteria, with an interest in both technological abilities and probiotic attributes.