Effects of 5-hydroxytryptophan and m-hydroxybenzylhydrazine associated to Lactobacillus spp. on the humoral response of broilers challenged with Salmonella Enteritidis

Heat stress in chickens induces temporal changes in the cecal microbiome concomitant with host enteric serotonin responses

Heat stress is a potent modulator of the avian neuroendocrine system with concomitant impact on the gut microbiome. As an interkingdom signaling molecule, serotonin is largely derived from the gut and found in large concentrations in the avian gut lumen. Despite the role of serotonin in animal stress physiology and related host-microbe interactions, whether heat stress alters avian enteric concentrations of serotonin is unknown. As such, the present study sought to determine whether acute or chronic exposure to moderate heat stress alters both enteric serotonin concentrations and the microbiome in the chicken gut. Chickens were, or were not, subjected to an acute (1 day), repeated acute (2 days) or chronic (6 days) moderate ambient cyclic heat stress (12h per day, 31°C). Enteric concentrations of serotonin were significantly decreased in the acute heat stress group (P < 0.05), and rebounded to become elevated in the chronic heat stress group (P < 0.05). Shotgun metagenomic sequencing revealed heat stress caused both functional and taxonomic changes in the cecal microbiome. Abundances of bacterial taxa that are known to interact with the host via the serotonergic system, including Lactobacillus spp., and Bifidobacterium spp., were significantly (P < 0.05) altered by heat stress. As these findings demonstrate that heat stress can alter serotonin concentrations in the chicken intestinal tract, with distinct outcomes depending on duration of the stressor, serotonergic signaling may serve as potential leverageable point of intervention in host-microbe interactions including foodborne pathogen colonization in the chicken gut. In addition, this study provides novel insight into the impact of acute and chronic heat stress on the avian microbiome, and its relationship to stress-driven changes in the enteric serotonergic system.

Co-evolution of the humoral immune and serotonergic systems in chickens selected for high or low blood antibody titer response to sheep red blood cells

Serotonin is a potent immunomodulatory neurohormone. Activities of the serotonergic and immune systems are often reported together in poultry studies with unidirectional analyses focused on serotonergic signaling mediating immune response. Considering serotonin's relevance across a range of immune-related poultry topics, elucidation of whether the immune system affects the serotonergic system can provide valuable insights into the bi-directionality of poultry neuroendocrine-immune interactions. The present study sought to determine whether selection for divergence in blood antibody titers to a non-pathogenic antigen coincides with parallel changes in the chicken's serotonergic system over the life of the bird. We utilized generations 49 and 50 male and female White Leghorn chickens (n = 10-12/chickens/line/sex/age) that have been selected long-term for high (HAS) or low (LAS) blood antibody response to intravenous sheep red blood cell injection. Because serotonin is predominantly produced in the gut and acts as an interkingdom signaling molecule, the first experiment sampled cecal tissue and luminal content samples from male and female HAS and LAS chickens at 293 days of age. In the second experiment, cecal tissue and luminal content, as well as plasma, were collected from HAS and LAS chickens at 28 and 56 days of age. Serotonin and its main metabolite, 5-hydroxyindoleacetic acid (5-HIAA), concentrations were determined in cecal tissue, luminal content, and plasma samples. Immunoglobulins IgA and IgY concentrations were analyzed in cecal luminal content or plasma, respectively. The HAS chickens had lower (p < 0.05) cecal IgA concentrations but higher (p < 0.05) plasma IgY concentrations than LAS chickens, suggesting a compensatory response within the intestinal tract following selection for high or low blood antibody titers. Serotonin and 5-HIAA concentrations in the ceca and plasma diverged (p < 0.05) in a pattern that mirrored ceca IgA and plasma IgY differences according to genetic line. The results from this study demonstrate that evolutionary selection pressure for humoral immune response in chickens causes responses in the serotonergic system at both enteric and systemic levels.

The Effect of Drinking Ionized Water on the Productive Performance, Physiological Status, and Carcass Characteristics of Broiler Chicks

Water treatment technologies have received great attention recently, as water is the most important nutritional element, and animals consume it daily in larger quantities than those of food. The ideal water treatment affects the chemical composition and physical properties of water, having a significant positive impact on the animal's physiology, productivity, and welfare. Studies conducted on water ionization devices for broiler chickens remain limited; therefore, this study was planned to investigate the effect of ionized drinking water on the productive performance, physiological status, and carcass characteristics of broiler chicks. A total of 900 one-day-old broiler chicks were randomly and equally assigned to three groups, each with six replicates (50 birds/replicate). The first group (C) received tap drinking water and served as a control, while the second group (T1) received ionized drinking water from an ionizing device that worked for 1 h/100 L. The third group (T2) received ionized drinking water from an ionizing device that worked for 2 h/100 L. Water analysis for each treatment was performed. Productive traits, such as weekly body weight, feed intake, and water intake, were recorded. Hematological parameters and biochemical constituents were measured according to the reference's description. Furthermore, carcass characteristics, such as carcass weight and dressing percentage, and bacterial count of the intestine, such as Lactobacilli and Coliform counts, were determined. From the results, ionized water (T1 and T2) had a negative ORP, which is often desirable as it suggests the presence of antioxidant properties and lower total dissolved solids (TDSs), heterotrophic plate count (HPC), and algal total count (ATC) than in tap water. The treated chicks showed higher final body weights and better feed conversion rates than the control. Ionized water also improved carcass quality characteristics, such as carcass weight and dressing percentage. T1 and T2 chicks exhibited higher hemoglobin, total protein, globulin, G and M immunoglobulin, and total antioxidant capacity (TAC) levels, as well as lower malondialdehyde (MDA) and low-density lipoprotein (LDL) levels than the control. Furthermore, they had lower pathogenic bacteria counts. Therefore, it is recommended to employ the ionizing approach for broiler chicken drinking water, particularly a 2 h/100 L ionization application, for better animal productivity, health, and welfare.

Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus)

Our production animals typically suffer poor welfare, which can be revealed by measuring the affective state these animals are in. Negative affective state is linked to poorer welfare, and can be measured as fearfulness. While continuing to research how to improve animal welfare, a compliment to reduce negative affective state could therefore be to reduce individuals' fearfulness, similar to how negative affective states are medicated in humans. A proposed mechanism for this is via the monoaminergic systems. This is based on previous studies across species that have linked the serotonergic system and fear-related behaviour. We here aimed to experimentally manipulate the serotonergic system in red junglefowl hens (Gallus gallus), the main ancestor of all domesticated chickens. We measured fearfulness as latency remaining immobile in a tonic immobility test, and did so both before and after our experimental manipulation. We set out to experimentally manipulate the serotonergic system via sub-chronic dietary treatment of 5-hydroxytryptophan (the precursor to serotonin). Our dietary manipulation of 5-hydroxytryptophan significantly reduced measured fearfulness in the manipulated hens, while latency in tonic immobility did not significantly change in our unmanipulated, control hens. This finding is promising since it indicates that increased tryptophan levels can be used to reduce fearfulness. Additionally, our result suggests that this can be done non-invasively via food (instead of injections), thus presenting a potentially feasible manipulation also for larger settings. Nevertheless, the serotonergic system is complex and its role in modulating behaviour in the fowl should be explored further to evaluate our findings, and more directly explored also in a production setting.

5-Hydroxytryptophan Suppresses the Abdominal Fat Deposit and Is Beneficial to the Intestinal Immune Function in Broilers

Background

Serotonin (5-HT), a monoaminergic neurotransmitter, involves in the regulation of many physiological functions. In the present study, the effects of 5-hydroxytryptophan (5-HTP), the precursor of 5-HT, on lipid metabolism and intestinal immune function in broiler chickens were investigated in chickens.

Methods

Two hundred broilers were divided randomly into two groups and fed separately with a corn-soybean basal diet (CD) or the basal diet supplemented with 0.2% 5-HTP.

Results

The results showed that 5-HTP reduced (P < 0.05) feed intake and the abdominal fat pad weight. 5-HTP treatment tended to upregulate the mRNA level of adiponectin receptor 1 (ADP1R) and ADP2R in abdominal fat but had no significant influence on their protein levels (P > 0.05). In 5-HTP-chickens, lipopolysaccharide exposure decreased secretory immunoglobulin A (sIgA) concentrations in serum and the duodenal contents. Expression of mRNA encoding interleukin (IL), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β) decreased after 5-HTP treatment; however, LPS increased expression significantly in 5-HTP-treated chickens compared with CD chickens. In 5-HTP-chickens, the phosphorylation of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) were reduced, but the phosphorylation of ribosomal p70S6 kinase (p70S6K) was increased in the duodenum.

Conclusion

In summary, the result suggests that dietary 5-HTP supplementation reduces accumulation of abdominal fat and is beneficial to intestinal immune function.

Listeria monocytogenes Inhibits Serotonin Transporter in Human Intestinal Caco-2 Cells

Listeria monocytogenes is a Gram-positive bacterium that can cause a serious infection. Intestinal microorganisms have been demonstrated to contribute to intestinal physiology not only through immunological responses but also by modulating the intestinal serotonergic system. Serotonin (5-HT) is a neuromodulator that is synthesized in the intestinal epithelium and regulates the whole intestinal physiology. The serotonin transporter (SERT), located in enterocytes, controls intestinal 5-HT availability and therefore serotonin's effects. Infections caused by L. monocytogenes are well described as being due to the invasion of intestinal epithelial cells; however, the effect of L. monocytogenes on the intestinal epithelium remains unknown. The main aim of this work, therefore, was to study the effect of L. monocytogenes on SERT. Caco2/TC7 cell line was used as an enterocyte-like in vitro model, and SERT functional and molecular expression assays were performed. Our results demonstrate that living L. monocytogenes inhibits serotonin uptake by reducing SERT expression at the brush border membrane. However, neither inactivated L. monocytogenes nor soluble metabolites were able to affect SERT. The results also demonstrate that L. monocytogenes yields TLR2 and TLR10 transcriptional changes in intestinal epithelial cells and suggest that TLR10 is potentially involved in the inhibitory effect observed on SERT. Therefore, L. monocytogenes, through TLR10-mediated SERT inhibition, may induce increased intestinal serotonin availability and potentially contributing to intestinal physiological changes and the initiation of the inflammatory response.

Localization and developmental expression of two chicken host defense peptides: cathelicidin-2 and avian β-defensin 9

In the first weeks of life young chickens are highly susceptible to infectious diseases due to immaturity of the immune system. Little is known about the expression of host defense peptides (HDPs) during this period. In this study we examined the expression pattern of two chicken HDPs, the cathelicidin CATH-2 and the β-defensin AvBD9 by immunohistochemistry in a set of organs from embryonic day 12 until four weeks posthatch. AvBD9 was predominantly found in enteroendocrine cells throughout the intestine, the first report of in vivo HDP expression in this cell type, and showed stable expression levels during development. CATH-2 was exclusively found in heterophils which decreased after hatch in most of the examined organs including spleen, bursa and small intestine. In the lung CATH-2 expression was biphasic and peaked at the first day posthatch. In short, CATH-2 and AvBD9 appear to be expressed in cell types strategically located to respond to infectious stimuli, suggesting these peptides play a role in embryonic and early posthatch defense.