Phenomenological and mechanistic insights into potential dietary nucleotide - probiotic synergies in layer chickens: A review

Despite their growing popularity as alternatives to antibiotic growth promoters (AGPs), the individual effects of nucleotides and probiotics on poultry gut functionality remain poorly understood. In addition, inconsistent outcomes are quite common in studies where these two additives have been used separately to modify gut function and related parameters in birds. These inconsistencies, which have limited the potential of probiotics and nucleotides as AGP replacements, stem from various factors and need to be addressed. Combining probiotics and nucleotides could potentially enhance their effectiveness and lead to more consistent outcomes in layer chickens. Since their mechanisms of action complement each other, some level of synergy is expected when used together. Both additives have been shown to support gut health, boost immune function, and improve performance in chickens when used individually. However, no studies have investigated the possible synergistic effects of nucleotides and probiotics in poultry. This review makes the case for combined use of probiotics and nucleotides in layer chickens by providing phenomenological and mechanistic insights into hypothetical synergistic effects. This paper highlights the need for AGP alternatives and reviews studies on the effects and mechanisms of probiotics and nucleotides in layer chickens when used individually. We then propose potential mechanisms for their synergistic effects on gut health, performance, and egg quality based on logical deductions from observed biological responses. These proposed mechanisms are hypothetical and require experimental validation. Finally, the review explores how this synergy could lead to more consistent outcomes and enhance the feasibility of AGP-free egg production.

A study on selected responses and immune structures of broiler chickens with experimental colibacillosis with or without florfenicol administration

BACKGROUND

Colibacillosis in broiler chickens is associated with economic loss and localized or systemic infection. Usually, the last resort is antibacterial therapy. Insight into the disease pathogenesis, host responses and plausible immunomodulatory effects of the antibacterials is important in choosing antibacterial agent and optimization of the treatment. Selected responses of broiler chickens experimentally infected with Escherichia coli (E. coli) and also those treated with florfenicol are evaluated in this study. Chickens (n = 70, 5 weeks old) were randomly assigned to four groups. The control groups included normal control (NC) and intratracheal infection control (ITC) (received sterile bacterial medium). The experimental groups consisted of intratracheal infection (IT) that received bacterial suspension and intratracheal infection with florfenicol administration (ITF) group.

RESULTS

Florfenicol reversed the decreased albumin/globulin ratio to the level of control groups (p > 0.05). Serum interleukin 10 (IL-10) and interferon-gamma (IFN-γ) concentrations decreased in IT birds as compared to NC group. Florfenicol decreased the serum interleukin 6 (IL-6) concentration as compared to IT group. Milder signs of inflammation, septicemia, and left shift were observed in the leukogram of the ITF group. Florfenicol decreased the severity of histopathological lesions in lungs and liver. Depletion of lymphoid tissue was detected in spleen, thymus and bursa of IT group but was absent in ITF birds. The number of colony forming units of E. coli in liver samples of ITF group was only slightly lower than IT birds.

CONCLUSIONS

Experimental E. coli infection of chickens by intratracheal route is associated with remarkable inflammatory responses as shown by changes in biochemical and hematological parameters. Histopathological lesions in lymphoid organs (especially in the spleen) were also prominent. Florfenicol has positive immunomodulatory effects and improves many of the lesions before the full manifestation of its antibacterial effects. These effects of florfenicol should be considered in pharmacotherapy decision-making process.

Impact of dietary-nucleotides and Saccharomyces cerevisiae-derivatives on growth-performance, antioxidant-capacity, immune-response, small-intestine histomorphometry, caecal-Clostridia, and litter-hygiene of broiler-chickens treated with florfenicol

Stress in poultry production is energy-demanding. Nucleotides and yeast cell-wall products are essential nutrients for broiler performance, gut function, and immune response. Antibiotics, like florfenicol, negatively affect the immune system. A total of 600 one-d-old broiler chickens (Cobb-500) were weighed and randomly allotted into four groups with three replicates each. The control group (G1) received the basal diet, G2 received a diet supplemented with a combination of nucleotides and Saccharomyces cerevisiae derivatives (250 g/Ton), G3 received the basal diet and medicated with florfenicol (25 mg/Kg body weight) in drinking water for 5 days, while G4 received a combination of nucleotides and Saccharomyces cerevisiae-derivatives (250 g/Ton) and medicated with florfenicol in drinking water. Growth performance criteria were recorded weekly. Blood, intestinal contents, small-intestine sections, and litter samples were collected to measure birds' performance, carcass yields, leukocytic counts, antioxidant capacity, antibody titres, phagocytic index, caecal Clostridia, intestinal histomorphometry, and litter hygiene. Nucleotide-supplemented groups (G2 and G4) revealed significant (p ≤ 0.05) improvements in feed conversion, and body weight, but not for carcass yields in comparison to the control. Dietary nucleotides in G2 elevated blood total proteins, leucocytic count, antioxidant capacity, and phagocytic index, while they lowered blood lipids and litter moisture and nitrogen (p ≤ 0.05). Dietary nucleotides in G4 ameliorated the immunosuppressive effect of florfenicol (p ≤ 0.05) indicated in reducing caecal Clostridia, improving duodenal and ileal villi length, and increasing blood albumin and globulin levels, and phagocytosis%. Supplementing diets with nucleotides and yeast products has improved the immune system and provided a healthier gut for broilers.

The effect of early administration of antibiotics or feeding a diet containing a coccidiostat on inflammatory responses and the morphological structure of selected organs of the immune system in young meat-type turkeys

It was assumed that early administration of enrofloxacin or doxycycline may impair immune function and alter the morphology of organs of the immune system in turkeys, and that diets containing the coccidiostat monensin, an ionophore antibiotic, can exert similar effects. The aim of this study was to determine whether early antibiotic administration or feeding a diet containing a coccidiostat affect immune function in young turkeys. The experiment had a completely randomized design, with 8 groups (a total of 3,080 one-day-old turkeys), 7 replicate pens per group and 55 birds per pen. The experiment had a 2-factorial design, with 4 treatments (C-control, M-monensin, E-enrofloxacin, and D-doxycycline) and 2 groups of birds (vaccinated and unvaccinated) per treatment. Control group birds did not receive the coccidiostat or antibiotics. Group M was administered monensin at 90 mg/kg feed for the first 5 d of life, group E received enrofloxacin at 10 mg/kg BW, added to drinking water, for the first 5 d of life, and group D received doxycycline at 50 mg/kg BW, added to drinking water, for the first 5 d of life. One-day old turkeys from groups C+, M+, E+, and D+ were administered live-attenuated vaccines against turkey rhinotracheitis (TRT) (Poulvac TRT; Zoetis, Parsippany, NJ) and Newcastle disease (ND) (Nobilis ND clone 30; Merck, Rahway, NJ) by coarse spray; 28-day-old birds were administered a subcutaneously injected inactivated vaccine against Ornithobacterium rhinotracheale (ORT) (Ornitin, Phibro, Poland). Turkeys from groups C-, M-, E-, and D- were not vaccinated. It was found that early administration of enrofloxacin or doxycycline, or feeding a diet containing monensin, did not weaken the immune system of turkeys. The administration of monensin, in particular when combined with vaccination, was least effective in inhibiting inflammatory responses. Histological changes in immunocompetent organs (fatty degeneration) were also most severe in birds receiving monensin, followed by those administered doxycycline and enrofloxacin. The observed changes were exacerbated by vaccination.

Recent developments in Salvia miltiorrhiza polysaccharides: Isolation, purification, structural characteristics and biological activities

In recent years, natural polysaccharides have attracted more and more attention and research because of their value in the medicine, beauty and food fields. Salvia miltiorrhiza is a traditional Chinese herb that has been used for thousands of years and has antidiabetic, antifibrotic, neuroprotective, antioxidation, anti-inflammatory and other effects. It mainly includes rosmarinic acid, tanshinone I, tanshinone IIA, tanshinone IIB, procatechualdehyde, polysaccharide and salvianolic acids. Salvia miltiorrhiza polysaccharide is a polysaccharide extracted and isolated from Salvia miltiorrhiza and has diverse biological functions, including antioxidation, anti-tumor, hepatoprotective, anti-inflammatory, immune regulatory and cardioprotective effect. In this review, the extraction, purification, structural characterization and biological activity of SMPs are summarized and new perspectives for the future work of SMPs were also proposed, we hope our research can provide a reference for further research on SMPs.

Gastrointestinal tract and neuroendocrine system responses of young turkeys to the early administration of antibiotics or feeding a diet containing a coccidiostat

This study investigated the effects of early and short-term administration of an antibiotic or feeding a diet containing a coccidiostat on gastrointestinal function and the blood levels of selected hormones in young turkeys. A total of 1540 Hybrid Converter turkeys were allocated to 4 groups on the day of hatch. Each group consisted of 7 pens with 55 birds per pen. Group ENR was treated with enrofloxacin for the first 5 d of life, group DOX received doxycycline for 5 d and group MON was administered monensin for 84 d. CON birds served as a control group without any antibiotic treatment or MON administration. An analysis of the activity of bacterial enzymes revealed that the cecal microbiota of turkeys were less sensitive to MON than to the other 2 antibiotics. Turkeys subjected to ENR and DOX treatments were characterized by lower (P < 0.05) extracellular activity of cecal bacterial β-glucosidase, compared with groups CON and MON. The extracellular activity of cecal bacterial α-galactosidase and β-galactosidase decreased significantly in response to the experimental treatment with DOX (P < 0.05 vs. CON). Turkeys treated with ENR had higher total activity of bacterial β-galactosidase than those administered DOX or MON. Despite the differences in the enzymatic activity of microbiota, the use of antibiotics did not affect the concentrations of total short-chain fatty acids or ammonia in the cecal digesta of turkeys. A diet containing MON and the early administration of ENR or DOX induced an increase in blood noradrenaline levels (P = 0.004) in 56-day-old turkeys. Early DOX use increased plasma cortisol concentrations (P < 0.001) and decreased plasma serotonin levels (P = 0.006) in 56-day-old turkeys. Over the entire experiment (up to 12 wk of age), the use of MON improved the BW gain of turkeys (P = 0.055) and feed conversion (P = 0.016), compared with the DOX treatment.

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.

Antimicrobial, immunological and biochemical effects of florfenicol and garlic (Allium sativum) on rabbits infected with Escherichia coli serotype O55: H7

Florfenicol (FFC) is a synthetic broad-spectrum antibiotic and garlic has a bactericidal action against coliforms. This study was carried out to compare the antimicrobial, immunological and biochemical effects of florfenicol and garlic, for their ability to treat enteropathogenic Escherichia coli serotype O55: H7 infection in rabbits. Four groups (G1-G4) were included. G1 group was the negative control; G2 group was the infected with a field-isolated strain of E. coli and untreated; G3 group was the infected+treated with FFC for 5 days; and G4 group was the infected+treated with garlic tablets for 14 days. The rabbits were observed for clinical signs, growth performance and mortality rates. Garlic-infused disks had a larger clear zone of inhibition than other antibiotic disks. Garlic treatment improved growth performance, biochemical parameters, and immunological response and reduced the fecal shedding and histopathological lesions in E. coli O55: H7 infected rabbits compared to the other groups. Colonization of E. coli more rapidly declined in G3 & G4 than in G2. Hepatic and intestinal gene expressions; tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were significantly elevated in G2 compared to the other groups, and their levels were elevated more in G3 than in G4. Serum interferon-gamma (IFN-γ) and phagocytic activity were significantly elevated in G4 compared to G3. G3 revealed macrocytic hypochromic anaemia that was confirmed histopathologically by moderate haematopoiesis of the bone marrow. In conclusion, garlic powder can reduce rabbit colibacillosis, like FFC, and can enhance the immune status of rabbits.

Synergistic use of florfenicol and Salvia miltiorrhiza polysaccharide can enhance immune responses in broilers

To explore the effect of florfenicol (FFC) combined with Salvia miltiorrhiza polysaccharide (SMPs) on immune function of Broilers. One hundred and twenty-one-day-old chicks were chosen and divided into 6 groups. The group A received standard basal diet only, the group B received a basal diet with FFC (0.15 g/L diet), and the group C, D, E received a basal diet with FFC (0.15 g/L diet) and SMPs (1.25 g/L, 2.5 g/L, 5 g/L diet)，the group F received a basal diet with SMPs (5 g/L diet). FFC can significantly inhibit the growth performance of broilers, but has no significant damage to the immune function of broilers. The combination of FFC and SMPs can improve the growth performance of broilers, increase the number of leukocyte subtypes in blood (P < 0.05), increase the number of Newcastle disease (ND) and avian influenza (AI) antibodies in blood, the number of immunoglobulins, and the content of cytokines (P < 0.05). In addition, it significantly improve the lymphocyte conversion rate of broiler peripheral blood (P < 0.05). So that, synergistic use of FFC and SMPs can enhance immune responses in Broilers.

Oxidative and Epigenetic Changes and Gut Permeability Response in Early-Treated Chickens with Antibiotic or Probiotic

The aim of this study was to compare the effect of the use of enrofloxacin and a probiotic containing Enterococcus faecium and Bacillus amyloliquefaciens strains in the first week of life of chickens on oxidative and epigenetic changes in molecules and intestinal integrity. The three treatments were as follows: the control group received no additive in the drinking water (GC); the second group (GP) received a probiotic preparation in the drinking water during the first five days of life, providing E. faecium strain 4a1713 at 1.0 × 107 CFU/L water and B. amyloliquefaciens 4b1822 at 1.0 × 107 CFU/L water, the third group (GA) received an antibiotic (enrofloxacin 0.5 mL/L water) in the drinking water during the first five days of life. The use of both enrofloxacin and a probiotic containing E. faecium and B. amyloliquefaciens strains in chickens' first week of life improved intestinal integrity and reduced inflammation and oxidative and epigenetic changes in the small intestine. This effect was evident both at 6 days of age and at the end of the rearing period.

Florfenicol induces oxidative stress and hepatocyte apoptosis in broilers via Nrf2 pathway

In order to explore the mechanism of liver injury induced by florfenicol (FFC) in broilers, one hundred and twenty broilers were randomly divided into six groups, twenty broilers in each group. Except for control group, the other five groups were given different doses of FFC (0.15 g/L, 0.3 g/L, 0.6 g/L, 1.2 g/L and 1.8 g/L) in drinking water. After five days of continuous use, blood was collected from the subpterional vein and the chickens' liver were obtained. Chicken weight gain and liver indices were calculated; blood routine analysis was performed; the oxidative stress and apoptosis of hepatocytes was detected. The results showed that compared with the control group, except for 0.15 g/L FFC, the other doses of FFC significantly decreased the weight gain, white blood cell (WBC) and platelet (PLT) contents in blood, 0.3 g/mL FFC and 1.8 g/L FFC significantly reduced the content of hemoglobin (RGB) (P < 0.05); all doses of FFC significant decreased red blood cell (RBC) increased Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) contents in serum of chickens (P < 0.05), and significantly decreased the contents of albumin (ALB) and total protein (TP) in serum (P < 0.05), but had no significant effect on alkaline phosphatase (ALP) contents(P > 0.05). FFC significantly increased malondialdehyde (MDA) content in serum and liver tissues, but decreased glutathione (GSH), Superoxide dismutase (SOD) and catalase (CAT) content (P < 0.05), and significantly inhibited the mRNA transcription and protein expression of antioxidant proteins nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H dehydrogenase quinone-1 (NQO-1)(P < 0.05). FFC also inhibited the content and the transcription level of cytochrome P4501A1(CYP1A1) and CYP2H1 in liver (P < 0.05). At the same time, FFC significantly promoted the apoptotic rate of hepatocytes and the mRNA transcription and protein expression of caspase-3 and caspase-6 (P < 0.05). With the increase of FFC concentration, liver injury became more and more serious, which affected liver function in chickens by inhibiting enzyme activity in Nrf2-ARE pathway to increase oxidative stress and promoting apoptotic protein expression to accelerate hepatocyte apoptosis.

Evaluation of humoral immune responses to enterotropic lentogenic VG/GA vaccine of Newcastle disease in commercial turkey poults (Meleagris gallopavo)

Background

Villegas-Glisson/University of Georgia (VG/GA) strain of Newcastle disease virus (NDV) is recommended for the initial vaccination of commercially reared turkey poults. However, the vaccine-induced antibody responses have not been studied in this species. The level of systemic humoral immune responses against the NDV was investigated in commercial turkey poults vaccinated with the VG/GA vaccine. One hundred eighty-two hybrid strain of turkey poults (Meleagris gallopavo) were divided randomly into vaccinated and unvaccinated groups. The vaccinated group was given the VG/GA vaccine at 10 and 20 days of age. To investigate the vaccine immunity, the level of specific IgY and IgA in serum samples were determined using ELISA and haemagglutination inhibition assays (HI). The biological half-life of maternal antibodies was also determined before the immunization.

Results

VG/GA-specific antibodies were detected in the vaccinated turkey poults and were significantly higher in the vaccinated group compared to the unvaccinated group. IgY and IgA antibodies showed a significant increase in titers 14 days after the second vaccination and reached a peak on day 35 of age. The correlation coefficient and intra-rater reliability showed a significant correlation between the HI titers and IgY/IgA ELISA values. Maternal IgY and IgA levels were found to decline in the serum with half-lifes of 7.68 ± 2.35 and 2.18 ± 0.82 days, respectively.

Conclusions

Enterotropic lentogenic VG/GA vaccine induced a marked humoral immune response against the NDV in turkey poults. The positive correlation between IgY and IgA highlights the role of these two antibody classes in controlling the Newcastle disease in turkey poults.

A reliable and cost-efficient TLC-HPLC method for determining total florfenicol residues in porcine edible tissues

It is still a challenge to solve the matrix interferences in veterinary drug residue analysis. In this study, we reported a thin layer chromatography (TLC)-high-performance liquid chromatography (HPLC) method for determining total florfenicol (FF) residues, expressed as florfenicol amine (FFA), in porcine edible tissues. The tissue homogenate were acid-hydrolyzed to liberate the bound residues and convert them into FFA. The hydrolysates were washed with ethyl acetate and subsequently extracted with ethyl acetate under alkaline conditions. The supernatants were concentrated through evaporation, defatted with hexane, purified by TLC and analyzed by HPLC at 225 nm. The optimal developing solvent for TLC purification was ethyl acetate-acetone-ammonium hydroxide mixtures (2:8:0.5, v/v/v). The method was fully validated according to decision 2002/657/EC, and could be used for the routine monitoring of FF residues in pig. TLC showed excellent purification efficiency, and was expected to solve the matrix interferences in veterinary drug residue analysis.

A reliable, simple and cost-efficient TLC-HPLC method for simultaneously determining florfenicol and florfenicol amine in porcine urine: application to residue surveillance

Violative residues of florfenicol (FF) in porcine edible tissues pose a potential risk for human health. In this study, urine was selected as target matrix for routine residue monitoring of FF in pig, and a thin layer chromatography (TLC)-high-performance liquid chromatography (HPLC) method was developed for simultaneously determining FF and florfenicol amine (FFA) in porcine urine. The urine samples were extracted with ethyl acetate under alkaline environment. The extracts were enriched through evaporation, purified by TLC and analysed by HPLC at 225 nm. A Waters Symmetry C₁₈ column was used for the separation of the two analytes. The mobile phase was acetonitrile-phosphate buffer mixtures (33.3: 66.7, v/v), and was pumped at 0.6 mL/min. The TLC-HPLC method was well validated and successfully applied to residue depletion study. Good analytical specificity was confirmed by the lack of interfering peaks at the retention times of FF and FFA. The standard curves showed good linearity (FF: y = 143064x - 1045.3, r= 0.9999; FFA: y = 275826x + 1888.8, r= 0.9999) over the range of 0.0625-8 μg/mL. The precision ranged from 0.83% to 11.66% and 2.19% to 8.75% for intraday and interday determination, respectively. The corresponding accuracy ranged from -13.38% to 10.78% and -12.15% to 7.14%, respectively. The limits of quantification (LOQs) for FF and FFA were 0.125 μg/mL. The residue depletion study showed that the concentrations of FF and FFA in urine were higher than those in edible tissues at three time points. This method was reliable, simple and cost efficient, and could be used to monitor FF residues in porcine edible tissue without slaughtering animals. TLC showed excellent purification efficiency and is expected to solve matrix interferences in veterinary drug residue analysis.

Immunomodulatory effects of orally administrated florfenicol in rainbow trout (Oncorhynchus mykiss) following experimental challenge with streptococcosis/lactococcosis

The purpose of the present work was to determine whether florfenicol (FFC) as the prominent broad-spectrum antibiotic could affect serum biochemical and immunological parameters, as well as immune-related genes expression in rainbow trout (55 ± 7.6 g) challenged with the Lactococcus garvieae and Streptococcus iniae. In the first trial, the doses of the pathogens for challenge test were determined based on LD50. The therapeutic dosage of the drug (15 mg.kg^-1 BW for 10 consecutive days) was administrated as medicated feed. After anesthesia, blood and kidney samples were collected from individual fish and were kept in deep freezing mode until the beginning of the measurements. Serum biochemical and enzymatic indices were measured using commercial kits. Immune parameters including total immunoglobulin level, lysozyme, ACH50, respiratory burst (RB), and phagocytic activities (PA) and the expression of immune genes namely TNF-α, IL-1β, IL-8, and IgM was evaluated. The levels of lysozyme and RB activities, as well as the expression of TNF-α and IL-1β genes, showed a significant increase in the FFC treated/infected fish compared to untreated diseased fish (P < 0.05). In contrast, serum total immunoglobulin and IgM-related genes expression were suppressed following drug administration represented by a significant reduction in untreated streptococcal infected fish compared to other treatments (P < 0.05). However, no significant effect of FFC was observed on serum ACH50 activity, PA values and IL-8-related gene expression (P > 0.05). These results demonstrated that FFC treatment could improve some physiological status including stress resistance and some liver function parameters, and much innate immunity was invigorated, but at the same time, the suppressive effects of FFC on acquainted immunity cannot be ignored.

Tulathromycin enhances humoral but not cellular immune response in pigs vaccinated against swine influenza

The effect of a standard, single dose therapy with tulathromycin was investigated on the postvaccinal humoral and cellular immune response in pigs vaccinated against swine influenza. Forty-five pigs, divided into 3 groups, were used (control not vaccinated (C, n = 15), control vaccinated (CV, n = 15), and experimentally received tulathromycin (TUL, n = 15)). For vaccination of pigs, an inactivated, commercial vaccine was used. Pigs from TUL group received single dose of tulathromycin intramuscularly, at the recommended dose (2.5 mg/kg body weight). Pigs from TUL and CV groups were vaccinated at 8 and 10 weeks of age. The specific humoral and cellular immune response against swine influenza virus (SIV) was evaluated. The results of present study showed that humoral postvaccinal response after vaccination against SIV can be modulated by treatment with tulathromycin. In pigs from TUL group, the significantly higher titers of anti-SIV-specific antibodies were observed 4 and 6 weeks after booster dose of vaccine. Simultaneously, T-cell-mediated immune response against SIV was not affected by tulathromycin. Our recent study confirmed the importance of defining the modulatory activity of tulathromycin because of its influence on the immune response to vaccines. Since the antibodies against hemagglutinin are crucial for the protection against SIV, the present observations should prompt further studies on the practical significance of recent results in terms of clinical implications (postvaccinal protection) in the field conditions.

Respiratory and GIT tract immune responses of broiler chickens following experimental infection with Newcastle disease's virus

Newcastle disease causes a lymphoproliferative response in the tracheal and intestinal mucosa of the infected birds. In this study, the Hitchner B1 and I-2 vaccine and challenging of ND field strains were used to evaluate the populations of T lymphocyte subsets infiltrated intestinal and tracheal, also to shed some light on cell-mediated immune response using enzyme-linked immunosorbent assay (ELISA) detecting chicken's serum interferon-γ. Three hundred-day-old broilers were randomly divided into four groups. Groups 1 and 2 received I-2 and B1 vaccines, respectively, while groups 3 and 4 were challenged-unvaccinated and unchallenged-unvaccinated groups. Blood samples were taken from five random chicks and were then tested with ELISA test. Three chicks of each group were euthanized after vaccine administration and also challenging with acute virus. Interferon-γ changes were significant in time (p < 0.001). Totally, there was no significant difference between I-2 and B1 groups. The number of CD3+, CD4+, and CD8+ cells of I-2 and B1 vaccinated group's intestine and the trachea samples was significantly increased compared with the negative control group (p < 0.001). The results indicated the significant increase in CD4+ and CD8+ in intestinal and tracheal tissues, while the level of interferon-γ of the vaccinated group was more than the unvaccinated one. Finding no significant differences between the vaccinated groups indicated the potential of both vaccines in producing CD4+ and CD8+ in the tracheal and intestinal tissues and the equality of interferon-γ production in the sera.

Validation of immunomodulatory effects of lipopolysaccharide through expression profiling of Th1 and Th2 biased genes in Newcastle disease virus vaccinated indigenous chicken

Background and Aim

Newcastle disease (ND) is considered one of the most important poultry diseases with chicken morbidity and mortality rates up to 100%. Current vaccination programs allow the use of live attenuated vaccines in the field to protect against the disease, which alone is inefficient and requires repeat booster doses. Toll-like receptor agonists (e.g., lipopolysaccharide [LPS]) as adjuvants are the ones, most extensively studied and have shown to be very promising in delivering a robust balanced immune response. In the present study, we have evaluated the potential of LPS to elicit a strong immune response with respect to the elicitation of both Th1 (cell-mediated) and Th2 (humoral) immune arms.

Materials and Methods

A total of 72 apparently healthy 1-day-old indigenous unvaccinated chicks were randomly divided into six experimental Groups A to F (n=12). At 8-week of age chicks in Group A, C, and E were vaccinated with live attenuated La Sota strain ND vaccine along with LPS, bovine serum albumin, and normal saline solution, respectively, and those in Group B, D, and E were kept separately without vaccination. Sampling was done on days 0, 1, 3, 7, 14, 21, 35, and 60 after vaccination. After vaccination and respective adjuvant application, Th1 and Th2 cytokine expression were measured in mRNA of both blood and tissue samples.

Results

The results were validated by, hemagglutination inhibition and enzyme-linked immunosorbent assay tests, to check for the humoral as well as cell-mediated immune response in blood serum levels. The results showed an increase in mRNA expression of the Th1 biased cytokines in Group A (LPS+NDV) as compared to the control groups. Similar mRNA expression pattern was seen in blood as well as tissue samples. Validation of results also indicates an increase in Cell-mediated Immunity as well as a humoral immune response in Group A (LPS+NDV).

Conclusion

The results of the study provided enough evidence to consider LPS as a potential vaccine adjuvants candidate against ND in chicken.

Specific antibody-mediated immunity in the reproductive tract of laying chickens immunized against Newcastle disease with conventional attenuated and inactivated vaccines

Despite the widespread and successful use of Newcastle disease (ND) vaccines, Newcastle disease virus (NDV) can seriously injure the reproductive tract of egg-laying hens, leading to rapid egg-drop and poor shell quality. Few published studies investigated local NDV-specific immune response in the reproductive tract after ND vaccination of hens. The present study investigated, for the first time, local NDV-specific antibody-mediated immunity in segments of the oviduct during the laying period. Specific pathogen-free (SPF) White Leghorn chickens were immunized following an ND vaccination programme applied in the field, which combined ND-attenuated vaccine (inoculated subcutaneously at one day, 2 weeks and 11 weeks of age) with inactivated vaccine (inoculated intramuscularly at 17 weeks). The infundibulum, magnum, isthmus and uterus (segments of the reproductive tract) were harvested at 28 weeks and 32 weeks of age (during the laying period). Supernatant from ex vivo tissue culture was collected and tested by: (i) haemagglutination inhibition (HI) test, (ii) commercial IDVet ND-enzyme-linked immunosorbent assay (ELISA) and (iii) NDV-specific IgG, IgM and IgA in-house ELISAs. For all sampling time points and oviduct segments, all samples were positive for commercial ND-ELISA and in-house ELISA-IgG. However, six of these ELISA-IgG positive samples yielded negative results when submitted to the HI test. Interestingly, NDV-specific IgM and IgA were detected frequently in the infundibulum and magnum as compared to the isthmus and uterus. These results show that the antibody immune response in the oviduct was induced by the timing of attenuated and inactivated ND vaccinations.

Enrofloxacin in therapeutic doses alters cytokine production by porcine PBMCs induced by lipopolysaccharide

The effect of enrofloxacin on cytokine secretion by porcine peripheral blood mononuclear cells (PBMCs) was studied. Twenty 8-20-week-old pigs were randomly divided into two groups: control (C, n = 10) and experimental (E, n = 10) were used. Pigs from group E received enrofloxacin at therapeutic dose for 5 consecutive days. Blood samples were collected at 0 (before antibiotic administration), 2, 4 (during antibiotic therapy) 6, 9, 14 21, 35, 49, and 63 d of study (after treatment). PBMCs of pigs from both groups were incubated with or without lipopolysaccharide (LPS). Ex vivo production on interleukin (IL)-4, IL-6, IL-10, INF-γ, and TNF-α were analyzed using ELISA assay. Intramuscular administration of enrofloxacin to healthy pigs for 5 consecutive days induced a transitory reduction of the ex vivo response of PBMCs to LPS in terms of IL-6 and TNF-α secretion. The level of IL-6 returned to day 0 level shortly after end of treatment, while the TNF-α production remained reduced 10 d after the end of treatment. Our results indicate that enrofloxacin given in vivo in therapeutic doses has an immunomodulatory effect through its capacity to inhibit ex vivo secretion of IL-6 and TNF-α by porcine PBMC after LPS stimulation.

Florfenicol induces more severe hemotoxicity and immunotoxicity than equal doses of chloramphenicol and thiamphenicol in Kunming mice

Amphenicols are effective, broad-spectrum antibiotics that function by inhibiting the peptidyl transferase activity of bacteria, while the drugs can also inhibit mitochondrial protein synthesis in eukaryotes through the same mechanism, which leads to multi-organ toxicity. Some side effects of each drug have been studied, while differences in the severity of the hemotoxicities and immunotoxicities of amphenicols have not been reported. Thus, it is important to identify, evaluate, and compare the potential hemotoxicities and immunotoxicities to guide their proper use in humans and animals, which will guarantee food safety and animal welfare. Ovalbumin-immunized Kunming mice were gavaged daily with amphenicols for seven days. Blood samples were collected for hematology analysis, and measuring anti-ovalbumin antibody levels and serum intereukin-2 concentrations. The bone marrow, spleen and thymus were collected for histopathology and apoptosis analyzes. Bone marrow nucleated cells (BMNCs) and splenocytes were harvested to determine their cell cycle stages and to analyze lymphocyte proliferation. The results demonstrated that amphenicols, especially florfenicol (FLO), induced cell cycle arrest and apoptosis of hematopoietic cells, and it changed the bone marrow hematopoietic microenvironment by decreasing the number of peripheral blood cells. Moreover, amphenicols, especially FLO, induced hypoplasia and atrophy of the spleen and thymus, induced cell cycle arrest, as well as splenocyte apoptosis, and decreased the proliferation and viability of lymphocytes and the humoral and cellular immunity of the treated mice. These results suggest that amphenicols induce hemotoxicity and immunotoxicity to some extent, and that FLO induces more severe toxicity than equal doses of chloramphenicol (CAP) and thiamphenicol (TAP).

Expression of recombinant Newcastle disease virus F protein in Pichia pastoris and its immunogenicity using flagellin as the adjuvant

Newcastle disease (ND), a highly contagious, acute, and potent infectious disease caused by Newcastle disease virus (NDV), has a considerable impact on the global poultry industry. Although both live attenuated and inactivated vaccines are used to prevent and control the spread of ND among chickens, the increasing number of ND outbreaks in commercial poultry flocks worldwide indicates that routine vaccinations are insufficient to control ND. Hence, efforts are being invested into developing alternative and more effective vaccination strategies. In this study, we focus on F protein, the neutralizing and protective antigen of NDV, and flagellin (FliC), a toll-like receptor 5 (TLR5) agonist that is an effective inducer of innate immune responses. We amplified F gene from velogenic NDV strain F48E8. The recombinant histidine (His)-tagged F protein was efficiently expressed in a Pichia pastoris (P. pastoris) eukaryotic system and verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blotting. The conditions for F protein expression in P. pastoris were optimal. The immunogenicity of F protein with FliC as the adjuvant was evaluated in a C3H/HeJ mouse model. FliC was found to enhance both F-specific and NDV-specific IgG responses and F-specific cellular immune responses following intraperitoneal co-administration with F protein. Thus, the recombinant F protein expressed by P. pastoris when used with flagellin as the adjuvant has potential as a subunit vaccine candidate.

Protective role of biogenic selenium nanoparticles in immunological and oxidative stress generated by enrofloxacin in broiler chicken

Presently most bacteria are becoming antibiotic resistant. Due to this there is a deficiency of potent antibiotics, therefore we have to preserve and improve the efficiency of existing antibiotics by mitigating the side effects. Enrofloxacin (EFX) is an important antimicrobial used in veterinary practice but it is known to exert immune suppression antioxidant stress. In the present study, we report on: (a) the biosynthesis of selenium nanoparticles (Se NPs), and (b) their protective effect in reducing adverse effects of EFX on broiler chicken. A potent bacterial strain, isolated from farm soil, has been identified as Pantoea agglomerans (GenBank: KU500622). It tolerates a high concentration of selenium dioxide (9 mM) and produces Se NPs under aerobic conditions. The obtained Se NPs are amorphous in structure and spherical in shape with sizes of less than 100 nm. The activity of cellular, humoral immune response and enzymatic and non-enzymatic antioxidants, has significantly been decreased as a result of EFX treatment. We investigated that Se NP supplementation greatly restores these values towards the control, and to even higher than those of the control. Adverse effects of EFX are prevented by simultaneous exposure to Se NPs (0.6 mg per kg of feed) in the diet of poultry chicken.

Long-term effects of early life microbiota disturbance on adaptive immunity in laying hens

Due to an interplay between intestinal microbiota and immune system, disruption of intestinal microbiota composition during immune development may have consequences for immune responses later in life. The present study investigated the effects of antibiotic treatment in the first weeks of life on the specific antibody response later in life in chickens. Layer chicks received an antibiotic cocktail consisting of vancomycin, neomycin, metronidazole, and amphotericin-B by oral gavage every 12 h, and ampicillin and colistin in drinking water for the first week of life. After the first week of life, chicks received ampicillin and colistin in drinking water for two more weeks. Control birds received no antibiotic cocktail and plain drinking water. Fecal microbiota composition was determined during antibiotic treatment (d 8 and 22), two weeks after cessation of antibiotic treatment (d 36), and at the end of the experimental period at d 175 using a 16S ribosomal RNA gene targeted microarray, the Chicken Intestinal Tract Chip (ChickChip). During antibiotic treatment fecal microbiota composition differed strongly between treatment groups. Fecal microbiota of antibiotic treated birds consisted mainly of Proteobacteria, and in particular E.coli, whereas fecal microbiota of control birds consisted mainly of Firmicutes, such as lactobacilli and clostridia. Two weeks after cessation of antibiotic treatment fecal microbiota composition of antibiotic treated birds had recovered and was similar to that of control birds. On d 105, 12 weeks after cessation of antibiotic treatment, chicks of both treatment groups received an intra-tracheal lipopolysaccharide (LPS)/human serum albumin (HuSA) challenge. Antibody titers against LPS and HuSA were measured 10 days after administration of the challenge. While T cell independent antibody titers (LPS) were not affected by antibiotic treatment, antibiotic treated birds showed lower T cell dependent antibody titers (HuSA) compared with control birds. In conclusion, intestinal microbial dysbiosis early in life may still have effects on the specific antibody response months after cessation of antibiotic treatment and despite an apparent recovery in microbiota composition.

The influence of enrofloxacin, florfenicol, ceftiofur and E. coli LPS interaction on T and B cells subset in chicks

This study aimed to investigate the influence of enrofloxacin, florfenicol, ceftiofur and E. coli LPS interaction on T and B subsets in thymus and spleen of newly-hatched chicks. A 126, 1-day-old chicks were administered enrofloxacin, florfenicol or ceftiofur in recommended doses according to the currently treatment schedule advises. E .coli LPS was given intravenously once at the dose of 200 μg kg⁻¹ BW on the 2nd day of experiment (d. e.). On the 6th and the 14th d. e. thymus and spleens were subjected to flow cytometry investigation.

The most significant changes were demonstrated in spleen. The antibiotics administration decreased the percentage of B and T cells subset. Moreover, this suppressive effect was enhanced by E. coli LPS administration. On the 6th d. e. the percentage of CD3⁺TCRγδ⁻, CD3⁺TCRγδ⁺, CD4⁺CD8⁻, CD4⁻CD8⁺ decreased significantly after ceftiofur and LPS treatment. A lower percentage of CD3⁺TCRγδ⁻, CD4⁻CD8⁺ and CD3⁺TCRγδ⁺ was observed in enrofloxacine and LPS treated group. The decrease percentage of CD3⁺TCRγδ⁺cells and Bu-1⁺ was found after florfenicol and LPS treatment. On the 14th d. e. a decreased percentage of CD4⁺CD8⁻ and increased percentage of CD4⁻CD8⁺ cells was shown in ceftiofur or enrofloxacine and LPS treated groups. In addition decreased percentage of CD3⁺TCRγδ⁺ was found in all antibiotic and LPS treated groups.

In this study, it was shown that enrofloxacine, florfenicol, ceftiofur treatment may change the proportions among lymphocytes subset and might have an impact on the immune response to bacterial endotoxins in chicks.

Toll-like receptor-based adjuvants: enhancing the immune response to vaccines against infectious diseases of chicken

Huge productivity loss due to infectious diseases in chickens is a major problem and, hence, robust development of the poultry industry requires control of poultry health. Immunization using vaccines is routine practice; however, to combat infectious diseases, conventional vaccines as well as new-generation recombinant vaccines alone, due to relatively weak immunogenicity, may not be effective enough to provide optimum immunity. With this in mind, there is a need to incorporate better and more suitable adjuvants in the vaccines to elicit the elevated immune response in the host. Over last few decades, with the increase in the knowledge of innate immune functioning, efforts have been made to enhance vaccine potency using novel adjuvants like Toll-like receptor based adjuvant systems. In this review, we will discuss the potential use of toll-like receptor ligands as an adjuvant in vaccines against the infectious diseases of chickens.

Flagellin a toll-like receptor 5 agonist as an adjuvant in chicken vaccines

Chicken raised under commercial conditions are vulnerable to environmental exposure to a number of pathogens. Therefore, regular vaccination of the flock is an absolute requirement to prevent the occurrence of infectious diseases. To combat infectious diseases, vaccines require inclusion of effective adjuvants that promote enhanced protection and do not cause any undesired adverse reaction when administered to birds along with the vaccine. With this perspective in mind, there is an increased need for effective better vaccine adjuvants. Efforts are being made to enhance vaccine efficacy by the use of suitable adjuvants, particularly Toll-like receptor (TLR)-based adjuvants. TLRs are among the types of pattern recognition receptors (PRRs) that recognize conserved pathogen molecules. A number of studies have documented the effectiveness of flagellin as an adjuvant as well as its ability to promote cytokine production by a range of innate immune cells. This minireview summarizes our current understanding of flagellin action, its role in inducing cytokine response in chicken cells, and the potential use of flagellin as well as its combination with other TLR ligands as an adjuvant in chicken vaccines.

Immune responses of poultry to Newcastle disease virus

Newcastle disease (ND) remains a constant threat to poultry producers worldwide, in spite of the availability and global employment of ND vaccinations since the 1950s. Strains of Newcastle disease virus (NDV) belong to the order Mononegavirales, family Paramyxoviridae, and genus Avulavirus, are contained in one serotype and are also known as avian paramyxovirus serotype-1 (APMV-1). They are pleomorphic in shape and are single-stranded, non-segmented, negative sense RNA viruses. The virus has been reported to infect most orders of birds and thus has a wide host range. Isolates are characterized by virulence in chickens and the presence of basic amino acids at the fusion protein cleavage site. Low virulent NDV typically produce subclinical disease with some morbidity, whereas virulent isolates can result in rapid, high mortality of birds. Virulent NDV are listed pathogens that require immediate notification to the Office of International Epizootics and outbreaks typically result in trade embargos. Protection against NDV is through the use of vaccines generated with low virulent NDV strains. Immunity is derived from neutralizing antibodies formed against the viral hemagglutinin and fusion glycoproteins, which are responsible for attachment and spread of the virus. However, new techniques and technologies have also allowed for more in depth analysis of the innate and cell-mediated immunity of poultry to NDV. Gene profiling experiments have led to the discovery of novel host genes modulated immediately after infection. Differences in virus virulence alter host gene response patterns have been demonstrated. Furthermore, the timing and contributions of cell-mediated immune responses appear to decrease disease and transmission potential. In view of recent reports of vaccine failure from many countries on the ability of classical NDV vaccines to stop spread of disease, renewed interest in a more complete understanding of the global immune response of poultry to NDV will be critical to developing new control strategies and intervention programs for the future.

Effects of in ovo vaccination and anticoccidials on the distribution of Eimeria spp. in poultry litter and serum antibody titers against coccidia in broiler chickens raised on the used litters

The present study reports the effects of various field anticoccidial programs on the distribution of Eimeria spp. in poultry litter and serum antibody titers against coccidia in broiler chickens raised on the used litters. The programs included in ovo vaccination and various medications with either chemicals, ionophores, or both. In general, serum samples from these chickens showed anticoccidial antibody titers when tested at days 7 and 14 post hatch with the peak response at day 43. Serum anticoccidial titers were highest in birds fed a non-medicated diet compared with those vaccinated or fed medicated diets. Total number of Eimeria oocysts and the composition of Eimeria spp. present in the litter samples from different treatment groups varied depending on the type of anticoccidial program. Oocyst counts in general ranged from 3.7×10(3) to 7.0×10(4) per g of litter. Importantly, both morphological and molecular typing studies revealed four major predominant Eimeria spp., E. acervulina, E. maxima, E. praecox, and E. tenella in the litter samples. Collectively, these results indicate that the field anticoccidial programs influenced the type and abundance of Eimeria spp. present in the litter samples and also modulated host immune response to Eimeria.

The influence of antibiotics on B-cell number, percentage, and distribution in the bursa of Fabricius of newly hatched chicks

Antibiotics are commonly used to prevent and treat poultry microbial infections, but certain antibiotic families depress humoral immunity, such as antibody production. Poultry humoral immunity depends on the normal functioning of the bursa of Fabricius and the B lymphocytes that mature in that gland. In this study, recommended therapeutic doses of enrofloxacin, florfenicol, or ceftiofur were administered to 2-d-old chicks. On d 7 post-hatch, bursae were sampled for histological, immunohistochemical, and flow cytometric determination of Bu-1-positive (Bu-1+) cell number, percentage, and distribution. The bursa of Fabricius from all treatment and control groups had normal morphology. The administration of antibiotics significantly decreased the number of Bu-1+ cells in the bursal medulla, with a simultaneous increase of these cells in the cortex. Flow cytometry revealed a significant decrease in the percentage of bursal Bu-1+ cells from all of the studied antibiotics: enrofloxacin (93.91 ± 3.27), florfenicol (87.84 ± 7.14), and ceftiofur (89.16 ± 5.68) compared with that of the control (96.48 ± 2.60). The combination of reduced percentages of Bu-1+ cells and a decrease in these cells in the medullary region suggests lower B cell maturation.

Feed supplemented with 3 different antibiotics improved food intake and decreased the activation of the humoral immune response in healthy weaned pigs but had differing effects on intestinal microbiota

The aim of this study was to determine the effects of 3 antibiotics used for pulmonary pathologies added in the feed of weaned pigs on growth performance, commensal microbiota, and immune response. At weaning, a total of 72 pigs were randomly assigned by BW and litter to 1 of the following diets: control (typical weaning diet), control + 400 mg of tilmicosin/kg, control + 600 mg of amoxicillin/kg, and control + 300 mg of doxycycline/kg. Individually penned pigs were slaughtered after 3 wk (12 pigs/treatment) or 4 wk (6 pigs/treatment). During the fourth week, all pigs received the control diet to test the residual effect of the antimicrobial supplementation. The antibiotic supplementation increased growth and feed intake during the first week (P < 0.01) and over the first 3 wk combined (P < 0.05). Gain-to-feed ratio tended to improve during the first week (P = 0.076) by the antibiotics compared with the control. Among the antibiotic treatments, no difference was observed in ADG and feed intake, which were also unchanged by the diet in the fourth week. The fecal enterobacteria counts were increased by amoxicillin on d 14 and 21 (P < 0.05 and 0.01, respectively) and were decreased by tilmicosin (P < 0.001) compared with the control. Amoxicillin decreased lactic acid bacteria (P < 0.01) counts compared with the control. The antibiotic supplementation tended to decrease total bacteria variability in the jejunum (Shannon index, P = 0.091) compared with the control. The antibiotic treatment decreased the mean total serum IgM concentration (P = 0.016) after 3 wk and did not change the mucosal histomorphometry of the small intestine. For tilmicosin, the observed positive action on piglet performance and feed intake can originate by the decreased costs of immune activation determined by the action on intestinal microbiota. For amoxicillin and doxycycline, the observation on intestinal and fecal microbiota seems to be not sufficient to explain their growth-promoting effect.

The immune enhancement of sodium lauryl sulfoacetate in chickens

The purpose of this study is to investigate feasibility of sodium lauryl sulfoacetate (SLS) as an immunoadjuvant in chickens. After treating with 62.5, 125, 250, or 500 mug/mL SLS in vitro, lymphocyte proliferation assay of chicken peripheral blood mononuclear cells showed that the OD(570) values of all experimental groups, as well as Con A-stimulated group, were significantly higher than that of the untreated control group. After injection with 1.0, 2.0, or 4.0 mg/kg of SLS for 3 consecutive days, chickens were vaccinated with an attenuated vaccine against Newcastle disease virus (NDV), and the immunoadjuvant effects of SLS were evaluated on the basis of immune organ index, antibody response, and CD(4) (+)/CD(8) (+) T-cell ratio. The results confirmed that SLS could enhance NDV-specific antibody response and increase CD(4) (+)/CD(8) (+) T-cell ratio in vivo. Furthermore, SLS could improve NDV-specific antibody response in thiamphenicol-treated chickens. These data indicate that SLS not only can improve humoral immune response but also reverse the immunosuppressive effect of thiamphenicol in chickens.