Diets containing phytobiotics, l-arginine, vitamin E and captopril modulate ascites syndrome-related genes expression in broiler chickens exposed to low ambient temperature

BACKGROUND

Our hypothesis centred on the potential to mitigate ascites outbreaks in birds exposed to cold stress by inhibiting pulmonary artery contraction through dietary intervention.

OBJECTIVE

This study aimed to evaluate the effect of natural and synthetic medications on growth performance, ascites-related parameters and the expression of ascites-related genes in the lung tissue of broiler chickens under low ambient temperature.

METHODS

We randomly assigned 450 one-day-old male Ross 308 chicks to six dietary treatments across five replicate pens, each containing 15 chicks. The treatments included a basal diet (control), and the basal diet was supplemented with hydroalcoholic extracts of sumac (HES, 200 mg/kg), Syrian mesquite (HEM, 200 mg/kg), l-arginine (40% above requirement), captopril (15 mg/kg) and vitamin E (100 mg/kg).

RESULTS

Diets containing HEM, l-arginine and vitamin E resulted in increased average daily gain on days 8-14 and 0-28, whereas HES showed a similar effect only during days 8-14 compared to the control diet (p < 0.05). Additionally, feed additives decreased packed cell volume, left and right ventricle volumes and systolic blood pressure (p < 0.05). Moreover, chickens fed the control and l-arginine diets exhibited higher levels of angiotensin converting enzyme (ACE) mRNA in lung tissue compared to those fed HES, HEM and captopril (p < 0.05). Meanwhile, supplementation with HEM and l-arginine increased the expression of inducible nitric oxide synthase (iNOS) mRNA in lung tissue compared to other treatments (p < 0.05). Regarding Cu/Zn-superoxide dismutase (Cu/Zn-SOD) expression, feed additives increased mRNA level in lung tissue, except for captopril (p < 0.05).

CONCLUSIONS

This study demonstrates that the plant extracts may reduce the incidence of ascites syndrome not only through their antioxidant properties but also by modulating the expression of ACE, iNOS and Cu/Zn-SOD genes.

Ross 708 broiler small intestine morphology and immunity improvements in response to in ovo Marek's Disease vaccine administration alone or in conjunction with in ovo and dietary supplemental calcifediol

Investigations were performed to determine the systemic immune and small intestine (SI) morphological responses of Ross 708 broilers to the Marek's Disease vaccine (MDV) administered alone or in conjunction with the in ovo and dietary administration of calcifediol (25OHD3). Live embryonated hatching eggs were assigned at random to 3 in ovo treatments at 18 d of incubation. Pre-specified in ovo treatments were: commercial MDV-alone-injected (50 µL) or commercial MDV containing 1.2 (MDV+25OHD3-1.2) or 2.4 (MDV+25OHD3-2.4) μg of 25OHD3. A noninjected control treatment was also included. For the growing phase, broilers received a commercial diet containing 250 IU of vitamin D3 /kg (control) or a commercial diet supplemented with 2,760 IU of 25OHD3 /kg (Hy-D diet). For determination of serum IgG, nitric oxide, and α-1-acid glycoprotein (AGP) at 14 and 40 d of age (doa), blood was collected from 1 bird per pen (48 total). In the duodenum, jejunum, and ileum of the same bird, villus length (VL), crypt depth (CD), VL to CD ratio (VCR), and villus surface area were also determined. There were no significant dietary x in ovo treatment interactions for any of the variables examined. However, birds fed Hy-D diets had lower serum AGP levels at 14 doa when compared to those fed un-supplemented commercial diets. Additionally, at 40 doa, birds in the MDV+25OHD3-1.2 and MDV+25OHD3-2.4 treatments experienced a decrease in serum AGP in comparison to those belonging to the noninjected and MDV-alone treatment groups. A higher jejunal VCR was observed at 14 and 40 doa in birds that belonged to the MDV+25OHD3-1.2 treatment when compared to those in the noninjected and MDV-alone treatment groups, and dietary Hy-D increased the VL of the duodenum and jejunum in birds at 14 and 40 doa when compared to those fed the commercial diet. In conclusion, both dietary or in ovo administration of 25OHD3 lowered inflammatory reactions and improved the SI morphology of broilers that were in ovo-injected with the MDV.

Beyond protein synthesis: the emerging role of arginine in poultry nutrition and host-microbe interactions

Arginine is a functional amino acid essential for various physiological processes in poultry. The dietary essentiality of arginine in poultry stems from the absence of the enzyme carbamoyl phosphate synthase-I. The specific requirement for arginine in poultry varies based on several factors, such as age, dietary factors, and physiological status. Additionally, arginine absorption and utilization are also influenced by the presence of antagonists. However, dietary interventions can mitigate the effect of these factors affecting arginine utilization. In poultry, arginine is utilized by four enzymes, namely, inducible nitric oxide synthase arginase, arginine decarboxylase and arginine: glycine amidinotransferase (AGAT). The intermediates and products of arginine metabolism by these enzymes mediate the different physiological functions of arginine in poultry. The most studied function of arginine in humans, as well as poultry, is its role in immune response. Arginine exerts immunomodulatory functions primarily through the metabolites nitric oxide (NO), ornithine, citrulline, and polyamines, which take part in inflammation or the resolution of inflammation. These properties of arginine and arginine metabolites potentiate its use as a nutraceutical to prevent the incidence of enteric diseases in poultry. Furthermore, arginine is utilized by the poultry gut microbiota, the metabolites of which might have important implications for gut microbial composition, immune regulation, metabolism, and overall host health. This comprehensive review provides insights into the multifaceted roles of arginine and arginine metabolites in poultry nutrition and wellbeing, with particular emphasis on the potential of arginine in immune regulation and microbial homeostasis in poultry.

Effects of Dietary Sodium Nitroprusside and NG-Nitro-L-Arginine Methyl Ester on Growth Performance, Some Organs Development Status and Immune Parameters in Broilers

This study was conducted to determine the effects of dietary supplementation of sodium nitroprusside (SNP), a nitric oxide (NO) donor, and NG-nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor, on growth performance, organ development, and immunity in broilers. A total of 560 one-day-old mixed-gender broiler chickens (ROSS 308) were divided into one control and seven experimental groups. The experimental groups were fed a basal diet supplemented with 25, 50, 100, and 200 ppm SNP, and 25, 50, and 100 ppm L-NAME in the starter and grower diets. Body weight gain increased in groups receiving 25-100 ppm L-NAME on day 21 and 100 ppm L-NAME on days 0-42. Feed intake increased in the group receiving 100 ppm L-NAME on all days. The feed conversion ratio improved in the group receiving 25 ppm L-NAME on days 0-21, whereas it worsened in groups with 100 and 200 ppm SNP on days 0-42. Serum antibody titers decreased in the 100 ppm L-NAME group on day 21. In conclusion, the supplementation of the NO synthase inhibitor L-NAME to the broilers' diet had a positive effect on the performance parameters, whereas the NO donor SNP worsened these parameters, especially on days 0-21.

Dietary inositol-stabilized arginine silicate numerically reduced woody breast severity in male Ross 708 broilers without altering growth

The woody breast (WB) myopathy is an unintended outcome of fast broiler chicken growth and high breast muscle yields. Myodegeneration and fibrosis in the living tissue are results of hypoxia and oxidative stress driven by lack of blood supply to muscle fibers. The study aim was to titrate a vasodilator ingredient, inositol-stabilized arginine silicate (ASI), as a feed additive to improve blood flow and ultimately, breast meat quality. A total of 1,260 male Ross 708 broilers were assigned to: 1) a control basal diet, or the control diet plus increasing ASI: 2) 0.025% ASI, 3) 0.05% ASI, 4) 0.10% ASI, or 5) 0.15% ASI. At d 14, 28, 42, and 49, growth performance was measured on all broilers and serum from 12 broilers/diet was analyzed for creatine kinase and myoglobin presence. On d 42 and 49, 12 broilers/diet were measured for breast width, then left breast fillets were excised, weighed, palpated for WB severity, and visually scored for degree of white striping (WS). At 1 d postmortem, 12 raw fillets/treatment underwent compression force analysis, and at 2d postmortem, the same fillets were analyzed for water-holding capacity. mRNA was isolated from 6 right breasts/diet at both d 42 and 49 for qPCR quantification of myogenic gene expression. Birds fed the lowest dose of 0.025% ASI had a 5-point/3.25% feed conversion ratio reduction compared to birds fed 0.10% ASI over wk 4 to 6 and reduced serum myoglobin at 6-wk of age compared to the control. Breasts from birds fed 0.025% ASI received 42% greater normal WB scores at d 42 compared to control fillets. At d 49, breasts from broilers fed 0.10 and 0.15% ASI received 33% normal WB scores. At d 49, 0.025% AS-fed broiler breasts showed no severe WS. Increased myogenin expression was observed in 0.05 and 0.10% ASI breast samples on d 42 and myoblast determination protein-1 expression was upregulated in breasts from birds fed 0.10% ASI on d 49 compared to the control. Therefore, a dietary inclusion of 0.025, 0.10, or 0.15% ASI was beneficial in reducing WB and WS severity and promoting muscle growth factor gene expression at age of harvest without diminishing bird growth or breast muscle yields.

Remarkable Effects of a Rhenium(I)-diselenoether Drug on the Production of Cathepsins B and S by Macrophages and their Polarizations

BACKGROUND/OBJECTIVE

Tumor-associated macrophages (TAMs) produce an excessive amount of cysteine proteases, and we aimed to study the effects of anticancer rhenium(I)-diselenoether (Re-diSe) on the production of cathepsins B and S by macrophages. We investigated the effect of Re-diSe on lipopolysaccharides (LPS) induced M1 macrophages, or by interleukin 6 (IL-6) induced M2 macrophages.

METHODS

Non-stimulated or prestimulated murine Raw 264 or human THP-1 macrophages were exposed to increasing concentrations of the drug (5, 10, 20, 50 and 100 μM) and viability was assayed by the MTT assay. The amount of cysteine proteases was evaluated by ELISA tests, the number of M1 and M2 macrophages by the expression of CD80 or CD206 biomarkers. The binding of Re-diSe with GSH as a model thiol-containing protein was studied by mass spectrometry.

RESULTS

A dose-dependent decrease in cathepsins B and S was observed in M1 macrophages. There was no effect in non-stimulated cells. The drug induced a dramatic dose-dependent increase in M1 expression in both cells, significantly decreased the M2 expression in Raw 264 and had no effect in non-stimulated macrophages. The binding of the Re atom with the thiols was clearly demonstrated.

CONCLUSION

The increase in the number of M1 and a decrease in M2 macrophages treated by Re-diSe could be related to the decrease in cysteine proteases upon binding of their thiol residues with the Re atom.

Dietary vasodilator and vitamin C/L-arginine/choline blend improve broiler feed efficiency during finishing and reduce woody breast severity at 6 and 7 wks

Woody breast has become a considerable economic concern to the poultry industry. This myopathy presents rigid, pale breasts characterized by replacement of lean muscle protein with connective tissue, a result of hypoxia and oxidative stress in a metabolically starved muscle with inadequate circulation. Hence, the objectives were to supplement broiler diets with ingredients specifically aimed to improve circulation and oxidative status. About 1,344 male Ross 708 broilers were assigned to 1 of 4 diets: 1) a basal diet (control), 2) basal diet plus a blend of 0.2% supplemental L-arginine, 0.17% choline bitartrate, and 0.03% vitamin C (blend), 3) 0.1% vasodilator ingredient (vasodilator), or 4) 0.02% Astaxanthin ingredient (AsX). At d 14, 28, 42, and 49, performance outcomes were collected on all birds and serum from 16 broilers/diet (n = 64) was analyzed for creatine kinase and myoglobin. Once weekly beginning on d 28, a subset of 192 broilers were measured for breast width. On d 42 and 49, breast fillets from 16 broilers/diet (n = 64) were palpated for woody breast severity, weighed, and analyzed for compression force at 1-day postmortem and water-holding capacity at 2-day postmortem. mRNA was isolated from 15 breast fillets/timepoint for qPCR quantification of myogenic gene expression. Data were analyzed using Proc Mixed (SAS Version 9.4) with the fixed effect of diet. Feed conversion ratio was improved in the blend and vasodilator-fed birds d 42 to 49, each by over 2 points (P < 0.05). Breast width was increased in the control on d 42 compared to the vasodilator and AsX-fed broilers (P < 0.05). At d 42, there were 12% greater normal fillets in blend diet-fed birds and 13% more normal scores in vasodilator-fed birds at d 49 compared to the control. At d 49, myogenin expression was upregulated in the AsX diet compared to blend and control diets (P < 0.05), and muscle regulatory factor-4 expression was increased by 6.5% in the vasodilator diet compared to the blend and AsX diets (P < 0.05). Blend and vasodilator diets simultaneously improved feed efficiency in birds approaching market weight while reducing woody breast severity.

Effects of the In Ovo and Dietary Supplementation of L-Ascorbic Acid on the Growth Performance, Inflammatory Response, and Eye L-Ascorbic Acid Concentrations in Ross 708 Broiler Chickens

Effects of the dietary and in ovo administration of L-ascorbic acid (L-AA) on the performance, plasma nitric oxide, and eye L-AA concentrations of Ross 708 broilers were investigated. At 17 days of incubation, live embryonated hatching eggs were randomly assigned to a non-injected or sham-injected (100 μL of saline) control group, or a group injected with either 12 or 25 mg of L-AA suspended in 100 μL of saline. Chicks received a commercial diet with or without 200 mg/kg of supplemental L-AA and were randomly assigned to each of 6 replicate floor pens in each in ovo injection-dietary treatment combination. Weekly live performance variables through 14 days of post hatch age (doa) and the eye weights in both sexes at 0, 7, and 14 doa were determined. At 0 and 14 doa, plasma nitric oxide levels and eye L-AA concentrations of one bird of each sex in each pen were determined. Dietary supplemental L-AA decreased feed intake and growth between 0 and 7 doa, but from 8 to 14 doa; all birds fed supplemental L-AA had a lower feed conversion ratio. At 14 doa, male chicks had higher eye L-AA concentrations and lower plasma nitric oxide levels when treated in ovo with 12 mg of L-AA. In conclusion, dietary L-AA may be used to improve feed conversion in the second week of broiler post hatch growth. However, the in ovo administration of 12 mg of L-AA can increase male eye L-AA concentrations and is effective in reducing their general inflammatory response.

Effect of sodium nitroprusside on feeding behavior, voluntary activity, and cloacal temperature in chicks

Nitric oxide (NO) is a well-known gaseous signaling molecule that is involved in a variety of physiological and pathological processes in vertebrates. The role of NO in physiological responses of birds has been investigated primarily using NOS inhibitors. Therefore, the effect of the absence of NO is well characterized. However, there is little knowledge on the effects of abundant NO in birds, which is the case in birds that have infections. Therefore, the purpose of the present study was to determine if intraperitoneal (IP) and intracerebroventricular (ICV) injections of sodium nitroprusside (SNP), a NO donor, affected feed intake, voluntary activity, cloacal temperature, crop emptying rate, and blood constituents in domesticated chicks (Gallus gallus) as model birds. We found that both IP and ICV injections of SNP significantly decreased feed intake while there was little effect on voluntary activity. Cloacal temperature was temporarily, but significantly, decreased by both types of injection of SNP. Additionally, both IP and ICV injections of SNP significantly decreased the crop emptying rate. The IP injection of SNP significantly increased the plasma concentrations of NO₂/NO₃, which are metabolites of NO, and corticosterone, and decreased the plasma glucose concentrations, while the ICV injection had no effect. The IP injection of SNP also showed the tendency to increase the nitrotyrosine level, to increase superoxide dismutase activity, and to decrease catalase activity in the plasma. These results suggest that under specific situations which produce abundant NO such as infection, NO would induce anorexia, hypothermia, inhibition of feed passage, and activation of the hypothalamus-pituitary-adrenal axis in chicks.

Effects of the In Ovo Injection of Vitamin D3 and 25-Hydroxyvitamin D3 in Ross 708 Broilers Subsequently Challenged with Coccidiosis: II Immunological and Inflammatory Responses and Small Intestine Histomorphology

In broilers challenged with coccidiosis, effects of in ovo vitamin D3 (D3) and 25-hydroxyvitamin D3 (25OHD3) administration on their inflammatory response and small intestine morphology were evaluated. At 18 d of incubation (doi), a 50 μL volume of the following 5 in ovo injection treatments was administrated: non-injected (1) and diluent injected (2) controls, or diluent injection containing 2.4 μg D3 (3) or 2.4 μg 25OHD3 (4), or their combination (5). Four male broilers were randomly allocated to each of eight isolated replicate wire-floored battery cages at hatch, and birds were challenged at 14 d of age (doa) with a 20x live coccidial vaccine dosage. One bird from each treatment-replicate (40 birds in each of 8 replicates per treatment) was bled at 14 and 28 doa in order to collect blood for the determination of plasma IL-1β and nitric oxide (NO) concentrations. The duodenum, jejunum, and ilium from those same birds were excised for measurement of villus length, crypt depth, villus length to crypt depth ratio (VCR), and villus surface area. In ovo injection of 2.4 μg of 25OHD3 resulted in a reduction in plasma NO levels as compared to all other treatments at 28 doa. Additionally, duodenal VCR increased in response to the in ovo injection of 25OHD3 when compared to the diluent, D3 alone, and the D3 + 25OHD3 combination treatments at two weeks post-challenge (28 doa). Therefore, it can be concluded that 2.4 μg of 25OHD3, when administrated in ovo at 18 doi, may be used to decrease the inflammatory reaction as well as to enhance the small intestine morphology of broilers during a coccidiosis challenge.

Dietary L-citrulline influences body temperature and inflammatory responses during nitric oxide synthase inhibition and endotoxin challenge in chickens

Recent studies have revealed the role of L-citrulline (L-CIT) in thermoregulation, but very little is known about the mechanisms involved. In this study, nitric oxide synthase inhibition and endotoxin-induced fever were used to investigate the effects of L-CIT on body temperature and inflammatory responses. In experiment 1, NW-nitro-L-arginine methyl ester (L-NAME, 150 mg/kg BW), was i. p. injected into chicks fed with basal (CON) or L-CIT diets for 14 days. In experiment 2, Lipopolysaccharide (LPS, 2 mg/kg BW) was i. p. injected following 21d feeding with CON or L-CIT diets. In experiment 3, chickens were injected with either L-NAME, LPS, or L-NAME + LPS following 26 days feeding with CON or L-CIT diets. The rectal (RT), ear (ET), and core body temperature (CBT) of chickens were examined. Results showed that L-NAME effectively decreased the RT, ET, CBT, and plasma NO concentration. In contrast, LPS increased NO levels and initiated hyperthermia by increasing RT, ET, CBT, and PGE2 levels. L-CIT diet reduced the mean CBT in experiment 1 and diminished the NO level, PGE2 level, and mean RT in experiment 3. Co-administration of L-CIT + LPS upregulated IL-6 expression, whereas, LPS injection alone induced IL-10, IL-1β, and TLR4 gene expressions. Therefore, this study reveals that L-CIT-induced hypothermia was related to NO inhibition and a decrease in PGE2 concentration. Conversely, LPS induced hyperthermia was associated with an increase in both NO and PGE2 concentrations.

L-Citrulline Influences the Body Temperature, Heat Shock Response and Nitric Oxide Regeneration of Broilers Under Thermoneutral and Heat Stress Condition

Heat stress (HS) adversely affects several physiological responses in organisms, but the underlying molecular mechanisms involved are yet to be fully understood. L-Citrulline (L-Cit) is a nutraceutical amino acid that is gaining research interest for its role in body temperature regulation and nitric oxide synthesis. This study investigated whether dietary supplementation with L-Cit (1% of basal diet) could ameliorate the effects of acute HS on thermotolerance, redox balance, and inflammatory responses of broilers. Ross 308 broilers (288 chicks) were subjected to two environments; thermoneutral at 24°C (TNZ) or HS at 35°C for 5 h, and fed two diets; control or L-Cit. The results showed that HS increased the ear, rectal (RT), and core body (CBT) temperatures of broilers, along with higher respiratory rate. The RT and CBT readings were intermittently affected with time effect, whereas, L-Cit supplementation lowered the mean CBT than the control diet. Antioxidant assays showed that superoxide dismutase was increased during HS, while, catalase was promoted by L-Cit supplementation. In addition, L-Cit induced glutathione peroxidase activity compared to the control diet during HS. Hypothalamic heat shock protein (HSP)-90 was upregulated by HS, but L-Cit downregulated heat shock factor (HSF)-1, and HSP 60 mRNA expressions. HSF 3 mRNA expression was downregulated by L-Cit under TNZ condition. More so, HS increased the plasma nitric oxide (NO) concentration but lowered the total NO synthase (tNOS) activity. In contrast, L-Cit supplementation limited NO production but increased the tNOS activity. Arginase activity was increased in the control fed group during HS but L-Cit supplementation lowered this effect. The NOS-COX pathway was significantly affected under TNZ condition, since L-Cit supplementation downregulated the mRNA expression of iNOS-COX2 in the hypothalamus, and further reduced the serum PGE2 concentration. Together, these data indicates that L-Cit influenced the antioxidant defense, heat shock response and nitric oxide regeneration both under thermoneutral and HS conditions; and that L-Cit may be directly and/or indirectly involved in the central regulation of body temperature.

Kinetic studies on clinical and immunological modulations by intramuscular injection of Escherichia coli LPS in laying hens

The present study investigated clinical and immunological modulations due to intramuscular injection of Escherichia coli LPS in 49-wk-old laying hens over 48 h post injection (p.i.). LPS induced characteristic sickness behavior but no significant body temperature alterations (P > 0.05). During experimental period decreases in blood albumin, calcium, phosphorus and tryptophan concentrations, hyperglycemia, increased plasma nitrite concentrations, leucopenia, decreased thrombocyte counts, lymphopenia, heterophilia and an increased heterophilic granulocyte/lymphocyte (H/L) ratio were observed after LPS administration. Time-dependent effects were shown on T and B cell subsets in caecal tonsils (CT) and on splenic CD3⁺/CD4⁺/CD8⁺ proportions, on IL-1β and -10 and inducible NO synthase mRNA expression in peripheral blood lymphocytes (PBL), liver, spleen and CT, and on the mRNA expression of the TLR4 in PBL, liver and spleen p.i. (P < 0.05). The main responding period of mentioned alterations due to LPS appears to include the period from 2 until 8 h p.i. According to the H/L ratio, the most stressful phase was 5 h p.i. T and B cell subsets in CT, the IL-1β and TLR4 mRNA expression in liver and plasma nitrite concentrations seemed to be affected for a longer period.

Evaluation of bee venom as a novel feed additive in fast-growing broilers

1. The present study was designed to evaluate purified bee venom (BV) as an alternative to antibiotics in broiler chickens. The experimental treatment diets were formulated by adding BV into a maize-soybean meal-based diet to give 0, 10, 50, 100, and 500 μg BV per kg of diet. 2. Dietary BV quadratically improved (P < 0.05) feed conversion ratio and increased body weight gain at 1-21 d as level in diet increased. Higher BV levels lowered relative weight of spleen (linear and quadratic, P < 0.05), bursa of Fabricius (quadratic, P < 0.05), and liver (linear and quadratic, P < 0.05) at 21 d of age. Relative breast meat yields were increased quadratically at 21 d and linearly at 35 d with supplementation levels. Dietary BV increased (linear and quadratic, P < 0.05) lightness (L*) value for meat at 21 d, decreased (linear, P < 0.05) ileal villus height and narrowed (quadratic, P < 0.05) width. 3. Dietary BV inclusion linearly increased the concentration of secretory immunoglobulin A (sIgA) on ileal mucosa at 21 d and decreased (quadratic, P < 0.05) nitric oxide contents in serum samples at 21 d and 35 d. Total short-chain fatty acids (SCFA) in caecal digesta were reduced with increasing venom in diets at 21 d of age. None of the serum parameters except for creatinine was affected by dietary BV. 4. It was concluded that dietary BV exhibited wide range of in vivo biological properties in broiler chickens and could be incorporated into feed to promote growth and animal health.

Interactive effects of dietary arginine and Eimeria acervulina infection on broiler growth performance and metabolism

The influence of dietary Arg concentration and Eimeria acervulina infection on broiler growth performance and plasma carotenoid, nitric oxide (NO), amino acid, and urea concentrations was evaluated. Male Ross × Ross 308 broilers (384 total) were fed a common diet for 10 d post-hatch and provided experimental diets formulated to contain 1.23 (HA) or 0.74% (LA) standardized ileal digestible Arg from 10 to 28 d. At 21 d, one-half of the broilers were switched to the opposite diet to create 4 dietary regimens where birds were fed the LA diet throughout, the LA diet replaced by the HA diet at 21 d, the HA diet throughout, or the HA diet replaced by the LA diet at 21 d. Broilers were orally inoculated 0 (uninfected) or 3.5 × 105 sporulated E. acervulina oocysts at 15 d, resulting in a factorial arrangement of 4 dietary regimens × 2 infection states (8 replicates/treatment). Overall (10 to 28 d) BW gain and G:F were greatest (P < 0.01) for birds fed the HA diet throughout, regardless of infection status. Eimeria acervulina infection decreased (P < 0.01) BW gain of birds from 15 to 21 d, and G:F was lowest (P < 0.05) for infected birds fed the LA diet during this period. There was no influence (P > 0.05) of E. acervulina on BW gain or G:F of broilers from 21 to 28 d. Plasma Arg, Lys, and Orn levels at 21 d indicated that the LA diet caused an imbalance in the Lys and Arg status of broilers, and E. acervulina infection increased (P < 0.01) the plasma concentration of these 3 amino acids. Diet × infection interactions (P < 0.05) were observed on 21 d for plasma carotenoids and NO, whereby infection decreased plasma carotenoids and increased plasma NO, but dietary Arg concentration only influenced these measures for uninfected birds. Thus, production of NO during E. acervulina infection was not impaired by dietary Arg limitation.

Nitric oxide and fever: immune-to-brain signaling vs. thermogenesis in chicks

Nitric oxide (NO) plays a role in thermogenesis but does not mediate immune-to-brain febrigenic signaling in rats. There are suggestions of a different situation in birds, but the underlying evidence is not compelling. The present study was designed to clarify this matter in 5-day-old chicks challenged with a low or high dose of bacterial LPS. The lower LPS dose (2 μg/kg im) induced fever at 3–5 h postinjection, whereas 100 μg/kg im decreased core body temperature (Tc) (at 1 h) followed by fever (at 4 or 5 h). Plasma nitrate levels increased 4 h after LPS injection, but they were not correlated with the magnitude of fever. The NO synthase inhibitor ( NG-nitro-l-arginine methyl ester, l-NAME; 50 mg/kg im) attenuated the fever induced by either dose of LPS and enhanced the magnitude of the Tc reduction induced by the high dose in chicks at 31–32°C. These effects were associated with suppression of metabolic rate, at least in the case of the high LPS dose. Conversely, the effects of l-NAME on Tc disappeared in chicks maintained at 35–36°C, suggesting that febrigenic signaling was essentially unaffected. Accordingly, the LPS-induced rise in the brain level of PGE2 was not affected by l-NAME. Moreover, l-NAME augmented LPS-induced huddling, which is indicative of compensatory mechanisms to run fever in the face of attenuated thermogenesis. Therefore, as in rats, systemic inhibition of NO synthesis attenuates LPS-induced fever in chicks by affecting thermoeffector activity and not by interfering with immune-to-brain signaling. This may constitute a conserved effect of NO in endotherms.

Effect of Astragalus polysaccharide and its sulfated derivative on growth performance and immune condition of lipopolysaccharide-treated broilers

This study evaluates the immunomodulating activities of Astragalus polysaccharide (APS) and sulfated APS (SAPS) in LPS-infected broiler chicks. SAPS was derived using the classic chlorosulfonic acid-pyridine method. On day 16, the birds were injected intramuscularly with 0.5 mL of either saline, APS (4 or 8 mg/kg of body weight (BW), shorten as APS-4 or APS-8) or SAPS (4 or 8 mg/kg of BW, shorten as SAPS-4 or SAPS-8) once a day for three successive days. On days 19 and 20, the birds were intraperitoneally injected with 0.5 mL of LPS (1mg/kg of BW). Saline was used as blank control. Compared with the blank control, LPS-treated birds showed lower daily body weight gain (BWG), average daily feed intake (ADFI), villus height and intraepithelial lymphocytes (IEL) number in jejunum, and higher feed conversion ratio (FCR, feed:gain), spleen index, plasma NO concentration, blood heterophil:lymphocyte (H:L) ratio, and the production of NO in the blood T lymphocytes. Compared with the LPS group, birds in APS-4, SAPS-4 and SAPS-8 groups showed decreased FCR (P<0.05). Moreover, SAPS increased BWG and jejunal villus height (P<0.05) at 8 mg/kg BW. Plasma NO concentration was lower in APS-8 group than that in LPS group (P<0.05). Both APS-8 and SAPS-8 treatments elevated the number of jejunal IEL (P<0.05), and decreased blood H:L ratio (P<0.05), respectively. Administration of APS or SAPS did not affect the ADFI, immune organ index, crypt depth and mucosal thickness of the jejunum, and the number of goblet cell. Our findings suggested that APS and SAPS possessed dose-dependent growth-promoting and immunomodulating effect, and was a potential development direction for immunomodulator under early LPS stimulation condition.

Altered monocyte and macrophage numbers in blood and organs of chickens injected i.v. with lipopolysaccharide

Lipopolysaccharide (LPS) is a Gram-negative bacteria cell wall component that activates monocytes and macrophages to produce nitric oxide (NO) from inducible nitric oxide synthase. Nitric oxide production in the plasma of chickens peaks 5-6-h post-i.v. LPS injection reflecting iNOS activation. To determine monocyte responsiveness after an i.v. LPS injection, a time course study was conducted examining the concentrations among peripheral blood leukocytes post-i.v. LPS injection in male and female chickens, the proportions among peripheral mononuclear leukocyte (PBMC; containing lymphocytes, thrombocytes, and monocytes) populations isolated from the blood samples collected at various times post-i.v. LPS treatment, and the ability of monocytes to produce NO with and without further LPS stimulation in vitro using the PBMC NO production assay. Additionally, monocyte extravasation activity was determined by analyzing macrophage proportions after the i.v. LPS injection in spleen, lung, and liver tissues. Blood was collected from male and female chickens at 0 h (pre-LPS injection control) and at 1, 3, 6, 24, and 48 h post-LPS injection, and additionally, at 72 h from female chickens. Tissues were collected 0, 1, 6, and 48 h post-i.v. LPS injection from male chickens. Monocyte concentrations dropped substantially by 1h in both males and females. In males, monocyte concentrations returned to control concentrations by 6h and increased at 24- and 48-h post-LPS injection, whereas in females, monocyte concentrations recovered more slowly, returning to near control concentrations by 24-48-h and increasing above control levels by 72 h. Lipopolysaccharide stimulated NO production by PBMC cultures established from blood samples obtained at various times post-LPS injection in vivo followed the same pattern as monocyte concentrations in the blood. Hence, NO concentrations within PBMC cultures were dependent upon the number of monocytes that were in the PBMC cultures isolated at different times post-i.v. LPS injection. Furthermore, macrophage proportions in spleen tissues responded similarly to monocyte concentrations in the blood, decreased in lung tissue, and varied widely in liver tissue throughout 48 h after an LPS injection. Monocytes and other leukocytes may attach to the endothelium post-i.v. LPS injection preventing the monocytes from entering the needle during blood collection resulting in what seems to be leukopenia in blood and in PBMC cultures attenuating NO production in PBMC cultures. Furthermore, monocyte differentiation and recruitment from the bone marrow is a likely contributor to the reconstitution and rise of monocyte concentrations in blood samples post-i.v. LPS injection.

Broiler pulmonary hypertensive responses during lipopolysaccharide-induced tolerance and cyclooxygenase inhibition

Bacterial lipopolysaccharide (LPS, endotoxin) triggers pulmonary hypertension (PH) characterized by an increase in pulmonary arterial pressure (PAP) that reaches a peak value within 20 to 25 min and then gradually subsides within 60 min. As the PAP subsides PH cannot be reinitiated, signifying the onset of a period of tolerance (refractoriness) to repeated LPS exposure. The present study was conducted to determine the duration of this tolerance, and to evaluate key mediators thought to contribute to LPS-mediated PH in broilers. Tolerance was shown to persist for 4 to 5 d after the initial exposure to LPS. In tolerant broilers supramaximal i.v. injections of LPS did not reinitiate PH, nor was a significant modulatory role for nitric oxide demonstrated. The pulmonary vasculature of tolerant broilers remains responsive to the thromboxane A(2) (TxA(2)) mimetic U44069, 5-hydroxytryptamine (5-HT, serotonin), and constitutive nitric oxide. Meclofenamate successfully blocked the conversion of arachidonic acid to vasoconstrictive eicosanoids such as TxA(2); nevertheless, meclofenamate failed to inhibit PH in response to LPS. Therefore, TxA(2) does not appear to be the primary vasoconstrictor involved in the PH response to LPS and neither does 5-HT. Broilers emerging from tolerance 5 d after the initial exposure to LPS exhibited interindividual variation in their PH responsiveness to a second LPS injection, ranging from zero response (individuals that remain fully tolerant) to large increases in PAP (post-tolerant individuals). Tolerance might be an important compensatory or protective mechanism for broilers whose pulmonary vascular capacity is marginally adequate under optimal conditions, and whose respiratory systems are chronically challenged with LPS in commercial production facilities. The key vasoconstrictors responsible for the PH elicited by LPS remain to be determined.