Metagenomic assembly reveals the circadian oscillations of the microbiome and antibiotic resistance genes in a model of laying hens

The increasing risks of antibiotic resistance genes (ARGs) in livestock feces have attracted global attention. However, how the rhythmic activity of ARGs changes in fecal microbiota remains largely unclear. In our study, we collected 52 fresh fecal samples every 6 h over 72 h from laying hens and characterized circadian oscillations of bacteria and ARGs using an approach based on assembled metagenome shotgun sequencing. We found that 14% of commensal bacterial taxonomic units fluctuated over 24 h. A total of 33 out of 281 ARGs and 17 of 574 mobile genetic elements (MGEs) featured rhythmic patterns in feces. lnuC and ANT(6)H-lb were the two most abundant ARGs with circadian oscillation identified from feces, and they increased during the day and decreased at night. Acetate, butyrate, propionate, and 78 out of 392 MetaCyc pathways relating to short-chain fatty acid (SCFA) metabolism featured circadian oscillations. Assessment of the above ARG-other element connections revealed that 17 ARGs presented strong correlations with 7 MGEs, and 2 SCFAs (acetate and propanoate) and bacterial species in feces. Structural equation model (SEM) analysis showed that ARGs were directly affected by microbial β-diversity and MGEs. These results showed a comprehensive map of ARGs over 24 h and revealed circadian oscillations of ARGs, which are influenced by key bacterial species, MGEs, and metabolites. Together, our findings advance comprehension of circadian oscillations of ARGs in the fecal microbiota and provide a reference for ARGs control and management.

Enantioselective characteristics, bioaccumulation and toxicological effects of chlordane-related compounds in laying hens

Chlordane-related compounds are ubiquitously detected in the environment and can transfer and accumulate to animals through food chain to cause adverse effects. In this study, the dynamic distribution and the enantiomeric profile of chlordane-related compounds in laying hens over time were investigated. The effect of these compounds on immune-associated cells in the intestinal tract and histopathology in some tissues were also evaluated after long-term exposure. The chlordane-related compounds preferentially accumulated in fat, followed by the intestines, ovum, and egg yolk during long-term exposure. The metabolites heptachlor epoxide and oxychlordane were mainly formed in the liver of hens by epoxidation or hydroxylation. The high accumulation ratios of trans-nonachlor and MC5 were found in ovum and egg yolk after long-term exposure, implying a greater risk to the hens' offspring. Chlordane-related compounds may cause abnormal lipometabolism and glycometabolism in liver of hens. Additionally, (-)-Cis-chlordane was dominant in all tissues of laying hens and its dominance increased over time. Conversely, (+)-isomer of metabolite oxychlordane was overwhelmingly dominant during the experiment. These findings about enantioselectivity, metabolic processes and toxicological effects are crucial in understanding the exposure risk of chlordane-related compounds.

Protective Effect of Nanoselenium on Renal Oxidative Damage Induced by Mercury in Laying Hens

This study investigated the effects of dietary nanoselenium (nano-Se) supplementation protecting from renal oxidative damages induced by mercury (Hg) exposure in laying hens. Furthermore, endoplasmic reticulum (ER) stress pathway was explored to reveal the protective mechanism of nano-Se. A total of 576 40-week-old Hyline-White laying hens were randomly allocated to 4 groups with 6 pens per group and 24 hens per pen. The experimental groups were as follows: control (basal diet), control + 27.0 mg/kg Hg, control + 5.0 mg/kg nano-Se, and Hg27.0 + 5.0 mg/kg nano-Se. The results revealed that dietary Hg exposure significantly reduced laying performance (P < 0.05) and egg quality (P < 0.05), whereas nano-Se supplementation partially reversed the reductions. Besides, dietary Hg exposure could induce histopathology damages and apoptosis in kidney, whereas nano-Se addition could alleviate these toxicities effectively. After Hg exposure, the activities and gene expressions of superoxidative dismutase (SOD) (P < 0.05), catalase (CAT) (P < 0.01), glutathione reductase (GR) (P < 0.05) and glutathione peroxidase (GSH-Px) (P < 0.05), and glutathione (GSH) content (P < 0.05) were significantly decreased, while the malondialdehyde (MDA) level was significantly increased (P < 0.05) in kidney. However, nano-Se supplementation partially reversed the levels and gene expressions of these antioxidant biomarkers in kidney. Furthermore, dietary Hg exposure significantly increased the gene expressions of PERK (P < 0.05), ATF4 (P < 0.05), CHOP (P < 0.05), IRE1α (P < 0.05), TRAF2 (P < 0.05), ASK1 (P < 0.05), Caspase-9 (P < 0.05), Caspase-8 (P < 0.05), Caspase-3 (P < 0.05), and Bax/Bcl-2 (P < 0.05), whereas nano-Se supplementation partially reversed these increases of gene expressions. In summary, this study provides evidence that dietary Hg exposure can induce renal oxidative damages, and elucidates an important role of ER stress pathway in nano-Se alleviating renal apoptosis in laying hens.

Effect of ellagic acid and mesocarp extract of Punica granatum on productive and reproductive performances of laying hens

In the present study, we determined the potential effects of ellagic acid and mesocarp extract of Punica granatum on the productive and reproduction performance of laying hens. Five treatment groups were setup: (1) control group (without ellagic acid), (2) 50 mg of ellagic acid, (3) 100 mg of ellagic acid, (4) 200 mg of ellagic acid, and (5) mesocarp extract of P. granatum. All the groups were investigated for feed intake, body weight, egg production, egg quality, fertility, hatchability, antioxidant status of serum and liver, lipid peroxidation, and antibacterial activities. Egg production, feed intake, and bodyweight were significantly increased (p < 0.05) with 100 mg of ellagic acid and P. granatum extract while no significant effect was observed on albumen and yolk weight, yolk index, yolk color, egg-shape index, and Haugh unit. Both ellagic acid and P. granatum extract significantly improved hatchability while 100 and 200 mg/kg of ellagic acid numerically decreased fertility. Besides, ellagic acid (100 mg/kg) and P. granatum extract significantly decreased malondialdehyde concentration and increased total antioxidant capacity, glutathione peroxidase, and total superoxide dismutase in serum and liver samples of laying hens (p < 0.05). The lipid peroxidation was decreased among the treatment groups, with 100 mg of ellagic acid and P. granatum extract showed the best activity. Moreover, ellagic acid demonstrated strong killing activity against Escherichia coli and Staphylococcus aureus while it was ineffective against methicillin-resistant S. aureus. Our results conclude that ellagic acid and P. granatum promoted egg production, hatchability, and antioxidant enzyme activities of the laying hens.

In vitro evaluation of the effects of methanolic plant extracts on the embryonation rate of Ascaridia galli eggs

The present study aims to find efficient alternatives to synthetic anthelmintics among ethno-veterinary herbs. Ascaridia galli eggs isolated from the worm uterus were exposed in vitro to methanolic extracts (ME) of nine plant species such as Achillea millefolium (AM), Artemisia absinthium (AA), Artemisia vulgaris (AV), Cicerbita alpina (CA), Cichorium intybus (CI), Inula helenium (IH), Origanum vulgare (OV), Tanacetum vulgare (TV), Tanacetum parthenium (TP). Flubendazole (FL), 0.5% formalin with dimethylsulfoxide and Petri dishes without the addition of reagents were used as positive, negative and untreated control respectively. The effects of the different ME at concentrations 0.500, 0.325, 0.200 mg/ml were assessed on the embryonic development (ED) of the eggs in duplicate. Logit analysis was used to calculate EC₅₀ values. A generalized linear mixed model, having plant species and concentration as fixed effect and day as repeated measure, was used to determine differences in ED. Estimated EC₅₀ was the lowest for FL at 0.11 mg/ml. CA and TV followed with 0.27 mg/ml and 0.32 mg/ml. ED for FL was significantly lower (25%) than that of CA (47%). The analysis showed 0.5 mg/ml of the ME of CA and TV significantly affected the ED at 35% and 42% inhibitions respectively. The ED for all ME showed similar pattern i.e., relatively higher efficacy in the first experimental week compared to the rest of the experimental period. The effect from all multicomponent extracts is time and dose dependent. The plants have promising results in inhibiting ED, contributing to the identification of alternative anthelmintic treatments.

Comfrey polysaccharides modulate the gut microbiota and its metabolites SCFAs and affect the production performance of laying hens

Effects of dietary supplementation of comfrey polysaccharides (CPs) on production performance, egg quality, and microbial composition of cecum in laying hens were evaluated. A total of 240 laying hens were allocated into 4 groups with 6 replicates per group. The laying hens were fed diets containing CPs at levels of 0, 0.5, 1.0, and 1.5 %, respectively. The results showed that the egg production rate increased by 5.97 %, the egg mass improved by 6.71 %, and the feed conversion rate reduced by 5.43 % in the 1.0 % supplementation group of CPs compared with those in the control group. The digestibility of ash, crude fat, and phosphorus was notably improved by the addition of CPs at 1.0 % (P < 0.05). The relative abundances of Bacteroidetes at the phylum level, Bacteroidaceae, Rikenellaceae, and Prevotellaceae at the family level were increased by CPs (P < 0.05). The relative abundances of Bacteroides, Megamonas, Rikenellaceae_RC9_gut_group, [Ruminococcus]_torques_group, Methanobrevibacter, Desulfovibrio, Romboutsia, Alistipes, and Intestinimonas at the genus level were increased by CPs (P < 0.05). Dietary supplementation of CPs could enhance the production performance of laying hens, which might be related to the improvement of nutrient digestibility and microbial community modulations in the cecum. Therefore, CPs have potential application value as prebiotics in laying hens.

Long-lasting effects of lipopolysaccharide on the reproduction and splenic transcriptome of hens and their offspring

Lipopolysaccharide (LPS) is ubiquitous in the environment and is released after the death of gram-negative bacteria, which may be related to inflammation and immunosuppression. However, its impact on the reproduction of animals and their offspring, especially the underlying mechanism need further elucidation. Here, we used laying hens as a model organism to investigate the effects of maternal exposure to LPS (LPS maternal stimulation) on animal and their offspring's immunity and reproductive performance, as well as the regulatory role of the transcriptome. We found that the LPS maternal stimulation could reduce the egg-laying rate of hens and their offspring, especially during the early and late laying stages. The transcriptome study of the spleen in F0, F1 and F2 generations showed that the maternal stimulation of the LPS affects the patterns of gene expression in laying hens, and this change has a long-lasting effect. Further analysis of DEGs and their enrichment pathways found that the LPS maternal stimulation mainly affects the reproduction and immunity of laying hens and their offspring. The DEGs such as AVD, HPS5, CATHL2, S100A12, EXFABP, RSFR, LY86, PKD4, XCL1, FOS, TREM2 and MST1 may play an essential role in the regulation of the immunity and egg-laying rate of hens. Furthermore, the MMR1L3, C3, F13A1, LY86 and GDPD2 genes with heritable effects are highly correlated with the egg-laying rate, may have an important reference value for further research. Our study reveals the profound implications of LPS exposure on immunity and reproduction of offspring, elaborating the impact of immune alteration on the egg-laying rate, emphasizing the regulatory role of intergenerational transmission of the transcriptome, implying that the environment parents being exposed to has an important impact on offspring.

Transcriptomics and transmission ultrastructural examination reveals the nephrotoxicity of cadmium in laying hens

The objective of this study was to reveal the effects of cadmium (Cd) on ultrastructural changes, oxidative stress, and transcriptome expression in the kidneys of laying hens. Seventy-two healthy Hy-Line brown laying hens at 41 weeks old were randomly allocated to four treatment groups with six replicates. The control group received a basal diet without additional Cd incorporation, and the other three treatment groups received diets supplemented with 15, 30, or 60 mg Cd /kg of feed. After 6 weeks of exposure, the results show that administration of 60 mg/kg Cd significantly reduced (P < 0.05) eggshell thickness. With an increase in the Cd concentration in feed, the concentrations of renal Zn and Fe also had changed. Renal histopathology and ultrastructure also showed aggravated damage to glomeruli and renal tubules and the deformation of nuclei and mitochondria in all Cd treatment groups. With an increase in Cd in feed, the activity of glutathione peroxide (GPX) and catalase (CAT) was significantly reduced (P < 0.05), while the activity of total antioxidant capacity (T -AOC) was decreased (P < 0.05) only in the 60 mg/kg Cd group. RNA-seq analysis revealed that 410 genes displayed differential expression (≥ 1.5-fold) in the 60 mg/kg supplementation group, compared to the control group. GO and KEGG pathway analysis results showed that Cd affected many genes involved in mitochondria and ion transport. In conclusion, this study elaborates the mechanisms underlying renal toxicity caused by Cd, which might provide target candidate genes for alleviating Cd poisoning in laying hens.

Construction of recombinant Pichia pastoris strains for ammonia reduction by the gdhA and glnA regulatory genes in laying hens

Ammonia emissions have become an important environmental challenge for the livestock industry. Probiotics are often used as additives to reduce ammonia, and the ammonia reduction efficiency of common probiotics is approximately 20-40%. In this study, we constructed a gdhA recombinant Pichia pastoris strain, glnA recombinant Pichia pastoris strain and gdhA-glnA Pichia pastoris recombinant strain using the gdhA and glnA genes, which have the potential function of reducing ammonia emissions. The results of in vitro fermentation showed that compared with the control, wild-type Pichia pastoris and pPICZA strains, the gdhA, glnA and gdhA-glnA recombinant strains significantly reduced ammonia emissions in laying hens (P < 0.05), with emission reduction efficiencies of 63.95%, 65.68% and 74.04%, respectively. The reason may be that the recombinant Pichia pastoris strains can convert ammonium nitrogen into amino acids for self-growth through ammonia assimilation, and reduce the pH, uric acid and urea content in the intestinal tract of livestock and poultry, and urease activity. Therefore, the construction of recombinant strains can provide technical support for reducing ammonia pollution in the livestock industry.

Impact of relative humidity on the laying performance, egg quality, and physiological stress responses of laying hens exposed to high ambient temperature

The present study investigated the effects of relative humidity (RH) on the laying performance, egg quality, and stress indicators of laying hens raised at high ambient temperatures. A total of 180 Hy-Line Brown laying hens (68-wk-old) were randomly allotted to one of the following three RH conditions for 12 h a day (9:00 a.m.-9:00 p.m.) over four weeks: low RH (LRH; 25% RH), moderate RH (MRH; 50% RH), and high RH (HRH; 75% RH); ambient temperature was 30 °C under all treatments. None of the RH treatments affected hen-day egg production, egg weight, or egg mass (P > 0.05). However, feed intake was lower in the HRH group than in the LRH group (P < 0.05). Plasma corticosterone (CORT) concentration on day 21, yolk CORT concentration on day 3, and albumen CORT concentration on day 7 following RH exposure were higher in the HRH group than in the LRH group (P < 0.05). Moreover, plasma HDL-cholesterol concentration on day 14 was higher in the HRH group than in the LRH group (P < 0.05). On days 3 and 14, the Haugh unit decreased (P < 0.05) in the LRH group compared with that in the MRH and HRH groups. The HRH-exposed laying hens showed the lowest (P < 0.05) eggshell thickness on day 14. The absolute weights of eggshell, yolk, and albumen decreased in the HRH group compared with those in the MRH and LRH groups. Overall, high RH lowered feed intake and egg quality except for the Haugh unit, and induced stress response as manifested by elevated plasma, yolk, and albumen CORT concentrations. To our best knowledge, the present study is the first to demonstrate the role of RH in triggering temperature stress responses in laying hens.

Effects of dietary supplementation with Ampelopsis grossedentata extract on production performance and body health of hens

To investigate the potential of Ampelopsis grossedentata extract used as a feed additive, laying performance, egg quality, yolk cholesterol, plasma biochemical parameters, intestinal histology, and gut microbiota of hens (n = 60) were determined between basal diet (CK) and dietary supplementation with A. grossedentata extract (RT) for 11 weeks. The laying rate in RT group was 6.3 percentage points higher than in CK group together with feed conversion rate decreasing. Significant upregulation of immunoglobulin indexes and downregulation of lipid-related indexes in RT group were also found in comparison with CK group, suggesting that dietary supplementation with A. grossedentata extract benefited in immunity enhancing and blood-fat depressing. Meanwhile, the villus height in duodenum and villus height to crypt depth ratio in duodenum and jejunum of RT group were significantly higher than that of CK group, indicating that dietary supplementation with A. grossedentata extract facilitated nutrient adsorption via intestinal histology changing. Moreover, the richness, diversity, and composition of gut microbiota in RT group significantly altered with a comparison of CK group, including beneficial bacterium and pathogenic bacterium, revealing that dietary supplementation with A. grossedentata extract could modify gut microbiota communities to affect intestinal adsorption and pathogen invasion. In addition, the lipid metabolism-related insulin signing pathway was significantly enriched by gut microbiota in RT group, which were conducive to egg production elevation via facilitating blood lipid amelioration and insulin resistance alleviation. These results provided a basis for A. grossedentata extract served as a feed additive in the hen industry.

Soya saponin improves egg-laying performance and immune function of laying hens

BACKGROUND

Soya saponin (SS), an active compound in soybean meals, has been widely studied in the medical field. However, it was considered as an anti-nutritional factor in poultry diets. The objective of this experiment was to measure the effects of dietary SS using three dietary treatments on egg-laying performance and immune function of laying hens. Birds were fed a low soybean meal basal diet (CON), a low-SS diet (50 SS) containing 50 mg/kg SS, or a high-SS diet (500 SS) containing 500 mg/kg SS for 10 weeks. At the end of the 5th and 10th week of the trial, samples were collected for analysis.

RESULTS

Results showed that with 50 mg/kg SS supplementation, the egg production rate, feed conversion ratio (FCR), and eggshell quality tended to be improved. Serum follicle stimulating hormone (FSH) and Interleukin-4 (IL-4) levels were also elevated as well as the peripheral blood LPS stimulation index, the proportion of B lymphocytes, and antibody titer of bovine serum albumin (BSA). We also found that mRNA levels of follicle stimulating hormone receptor (FSHR) in ovarian, nuclear transcription factor kappa B (NF-κB), Transforming growth factor (TGF-β) and interferon γ (IFN-γ) in spleen were up-regulated at the end of the trial. Additionally, dietary 50 mg/kg SS improved the ileal flora via up-regulating the relative abundance of Lactobacillus, Romboutsia and Lactobacillus delbrueckii. Although the immune related indicators were improved with 500 mg/kg SS supplemented, it seemed to have a negative influence on the laying-performance. Specifically, serum alanine aminotransferase (ALT), alkaline phosphatase (ALP), and the ratio of IFN-γ to IL-4 were increased in the 500 SS group at the end of the trial. The mRNA levels of gonadotropin releasing hormone 1 (GnRH1) in Hypothalamus, the estrogen related receptor (ERR) in ovaries were downregulated as well as the egg production rate during the trial with 500 mg/kg SS supplemented.

CONCLUSIONS

The egg production performance was improved by dietary supplemented with 50 mg/kg SS via increasing ovarian FSHR transcription level and serum estrogen level. A beneficial shift in intestinal microflora was recorded, and the immune function of laying hens was also improved with 50 mg/kg SS supplementation. Surprisingly, the long-term supplementation of 500 mg/kg SS exerted a negative impact on the laying performance and physiological functions of the liver of laying hens.

Protective effects of Aloe vera powder supplementation on some quantitative and qualitative characteristics of egg, histopathological changes and serum biochemistry of laying hens fed by Aflatoxin B1

In the recent years, the use of medicinal plants to reduce the effects of mycotoxins in foods and feeds has been considered. This study was conducted to investigate the effects of Aloe vera on performance, serum biochemical parameters and liver histopathology in laying hens fed on aflatoxin B1 (AFB1)-contaminated diet. Seventy-two White Leghorns (Hy-Line W-36) were randomly allocated to four treatments. 1) basal diet (control), 2) control plus 1.00 mg kg^-1 AFB1, 3) control diet plus 1.00 mg kg^-1 AFB1 + 100 ppm Aloe vera powder, and 4) control diet plus 1.00 mg kg^-1 AFB1 + 300 ppm Aloe vera powder. Each treatment consisted of three replicates of 6 birds. Egg weight and Haugh units were not affected by AFB1. Egg production and eggshell thickness were lower for groups fed 1.00 mg kg^-1 AFB1. Egg production, egg weight and eggshell thickness were improved by incorporation of Aleo vera in the AFB1 contaminated feed but were not significant. Chickens fed AFB1 had significantly lower aspartate aminotransferase (AST), alanine aminotransferase (ALT) and uric acid and higher cholesterol than other groups. Aloe vera powder improved levels of cholesterol, uric acid, AST, and ALT. AFB1 also caused histopathological changes in liver tissues, such as vacuolar degeneration, fatty infiltration, and necrosis. The addition of Aloe vera powder to the aflatoxin containing diet reduced the severity of lesions in liver. The data demonstrated the ability of Aloe vera to reduce the adverse effects of AFB1 exposure in laying hens.

Effect of Glycine Nano-Selenium Supplementation on Production Performance, Egg Quality, Serum Biochemistry, Oxidative Status, and the Intestinal Morphology and Absorption of Laying Hens

The objective of this study was to investigate the feasibility of using glycine nano-selenium (NS-Gly) as a feed supplement and to evaluate its influence on production performance, egg quality, serum biochemistry, oxidative status, and the intestinal morphology and absorption of laying hens. A total of 864 hens at 40 weeks were randomly assigned into six groups including the basal diet (control, 0.13 mg Se/kg); basal diet + 0.30 mg Se/kg (Na₂SeO₃) diet; and basal diet + 0.15, 0.30, 0.45, and 0.60 mg Se/kg (NS-Gly) diet. After 8 weeks of Se supplementation, no difference was observed among the treatments on production performance and egg quality (P > 0.05). The levels of albumin (ALB) and alanine aminotransferase (GPT) were significantly influenced by dietary Se supplementation (P < 0.05). In the serum, the level of glutathione peroxide (GSH-Px) was significantly increased in the groups with the dietary NS-Gly supplementation (P < 0.05). The superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) levels in all groups of NS-Gly supplementation had a remarkable increase (P < 0.05). In the liver, GSH-Px was significantly increased in 0.45 and 0.60 mg/kg NS-Gly groups (P < 0.05). The activities of SOD and catalase (CAT) were significantly increased in the groups of 0.30 mg/kg NS-Gly diet (P < 0.05). The results of intestinal morphology showed that the crypt depth was affected by higher dose groups of NS-Gly diets in the duodenum, and the differences (P < 0.05) were obtained in villus height, the crypt depth, and the V/C in the jejunum. In the ileum, a significant increase (P < 0.05) of villus height was observed in 0.15 and 0.3 mg/kg Se-added groups. The V/C was the highest in the SS groups (P < 0.05). The mRNA levels of solute carrier family 3 member 1 (rBAT), solute carrier family 6 member 19 (B⁰AT1), and solute carrier family 15 member 1 (PepT1) increased at different degrees in the duodenum, especially in 0.15 and 0.60 mg/kg NS-Gly groups (P < 0.05). In the jejunum, the expression of B⁰AT1 was similar to that in the duodenum, and the expression of rBAT increased significantly in the 0.30 and 0.45 mg/kg NS-Gly groups (P < 0.05). The mRNA level of PepT1 increased significantly in the 0.30 mg/kg SS group. Conclusively, dietary NS-Gly supplementation could improve the antioxidant capacity, as well as the structure of small intestine in laying hens, although have no significant effects on the production performance and egg quality.

Promotion of Egg Production Rate and Quality Using Limosilactobacillus oris BSLO 1801, a Potential Probiotic Screened from Feces of Laying Hens with Higher Egg Productive Performance

In this experiment, laying hens were divided into a high productive group (group H) and a low productive group (group L). The purpose of this experiment was to screen and isolate a potential probiotic associated with the laying rate from group H by comparing the results via 16S rDNA high-throughput sequencing. The high-throughput sequencing analysis results showed that there were some differences in the composition of the gut microbiome between groups H and L on the Phylum and Genus levels. Through isolation and identification, we screened 16 lactobacilli strains. Among the 16 strains, S5 showed good acid tolerance, bile salt tolerance, and cholesterol degradation. Therefore, we chose strain S5 (identified as Limosilactobacillus oris, named Limosilactobacillus oris BSLO 1801) as a potential probiotic to promote the productivity of ordinary laying hens. During the animal experiment, 288 Hy-line white hens (30 weeks old) were divided into four groups, with six replications (n = 12) per group. The control group received the basic diet, and the treatment groups received the same basic diet supplemented with 10⁷ CFU/kg, 10⁸ CFU/kg, and 10⁹ CFU/kg of BSLO 1801. The laying hens were acclimated to the environment for 1 week before the initiation of the experiment. Dietary supplementation with 10⁷ CFU/kg and 10⁹ CFU/kg of BSLO 1801 increased the laying rate significantly, and the potential probiotic improved the egg weight in all treatment groups. Additionally, the cholesterol content of the yolk dropped significantly in the 10⁹ CFU/kg group, and the weight of egg yolk was significantly increased in all treatment groups. However, no significant differences in eggshell strength, eggshell thickness, protein height, and Haugh unit were observed among the four groups. These results revealed that lactobacilli spp. are important bacteria of the intestinal microbiome in highly productive laying hens, and BSLO 1801 was isolated as a potential probiotic. Through these animal experiments, we also found that adding BSLO 1801 to the basic diet of laying hens could effectively improve the laying rate, average egg weight, and yolk weight and reduce the cholesterol content in egg yolk.

Ammonia reduction by the gdhA and glnA genes from bacteria in laying hens

Ammonia emissions are a high-focus pollution issue in the livestock industry. Ammonia-degrading bacteria can assimilate ammonia nitrogen as a nitrogen source to promote their growth and reproduction, providing an environmentally friendly, low-cost and safe biological way to reduce ammonia emissions from livestock. However, it remains unclear how ammonia-degrading bacteria reduce ammonia emissions from animals and what are the key ammonia assimilation genes. In the present study, two strains with ammonia nitrogen-degrading abilities (Enterococcus faecium strain C2 and Bacillus coagulans strain B1) were screened from laying chicken caecal and faecal samples and reduced ammonia emission rates by 53.60% and 31.38%, respectively. The expression levels of the ammonia assimilation genes gdhA, glnA, and GMPS increased significantly. On this basis, we successfully constructed three clone strains (PET-GDH, PET-GS, and PET-GMPS) that expressed the gdhA, glnA and GMPS genes in E. coli, respectively, to verify their ammonia-reducing activities. The results of an in vitro fermentation study showed that the ammonia production of the PET-GDH and PET-GS groups was significantly lower than that of the empty vector group (p < 0.05), with ammonia emission reduction rates of 55.5% and 54.8%, respectively. However, there was no difference between the PET-GMPS and empty vector groups. These results indicate that gdhA and glnA may be key genes involved in the bacterial-mediated regulation of ammonia emissions by laying hens, and ammonia emissions may be reduced by regulating their expression. The results of the present study provide a theoretical basis for the construction of engineered bacteria to reduce ammonia production in animals.

Effect of in ovo injection of serotonin on the behavior and hormone level in laying hens

Feather pecking is a typically abnormal behavior that significantly impacts breeding efficiency and animal welfare in the egg production sector. Serotonin (5-HT) is essential for neuronal development and behavioral regulation. This study evaluated the effects of birds' behavioral development (including feather pecking) and changes in serum hormones in chickens followed in ovo injection of 5-HT. On day 11, incubated eggs were injected with 5-HT at 0 (saline control), 5 ug (low) or 15 ug (high) (n = 166 per treatment). The hatched female chicks were raised under similar conditions up to 20 weeks of age (n = 60 per treatment). Birds' behaviors were recorded using a digital video recording system. The time to first vocalize and first move, along with the duration of vocalization and escape attempts during the isolation test, during isolation test were analyzed on day 1, and week 4, 8, 12, 16 and 20. Blood samples were collected followed behavioral tests (n = 5/treatment). The expression of 5-HTR1A genes in the hypothalamus was measured by real-time PCR. Compared to controls, 5-HT administrated pullets had greater body weight (P < 0.05) with an improved feed conversion rate (P < 0.05) as well as higher serum concentrations of norepinephrine (NE) regardless of their doses. In addition, serum dopamine (DA) concentrations were lower in both high- and low-dose pullets at 8 and 12 weeks of age (P < 0.05). Also, a decrease in fearfulness response was observed based on the test to vocalize and duration of vocalization (P < 0.05). Further, this exhibited a lesser frequency of total aggressive behavior compared with the chicks in the control group, especially at 8 weeks of age (P < 0.05), where it is associated with elevated serum 5-HT concentration and upregulated hypothalamic expression of 5-HTR1A (P < 0.05). The changes of these hormone concentrations and gene expressions suggested that 5-HT accumulation in early embryonic stages may alter both the adrenergic and serotonergic systems, which could further regulate the isolation behavior and improve birds' growth performance to a certain extent.

Investigation of a potential electrogenic transport-system for myo-inositol in the small intestine of laying hens

1. Myo-inositol (MI) is an essential metabolite for cell function in animals and humans. The aim of this study was to characterise the transport mechanism of MI in the small intestine of laying hens as there is a lack of knowledge about the MI uptake mechanisms. The hypothesised secondary active, cation coupled transport of MI was assessed by electrophysiological measurements with Ussing chambers, and was compared to the electrophysiology of glucose transport.2. Twenty-six laying hens were used. The potential ion-dependent transport was tested in tissue of the small intestine. Barrier function of the tissue was shown by determining the transepithelial resistance. During the experiments, mucosal and serosal buffers were sampled to measure time-dependent changes in MI concentrations. Samples from eight hens were further used for Western blot analyses of the jejunal apical membranes.3. Active MI transport, indicated by changes in the short circuit current after MI addition, could not be demonstrated in the Ussing chambers experiments. MI was further not detectable in the serosal buffer, nor in the lysates of mucosal tissue cytoplasm nor lipids. Thus, there was no evidence for a MI transport or absorption. However, Western blot analyses of the jejunal apical membrane revealed signals indicated the expression of the MI transport proteins SMIT-1 and SMIT-2.4. In conclusion, the MI transport process in the chicken intestine is more complex than it was presumed and is probably influenced by still unknown regulations or metabolic processes.

Breed differences in the expression levels of gga-miR-222a in laying hens influenced H2S production by regulating methionine synthase genes in gut bacteria

BACKGROUND

The microbiota in the cecum of laying hens is crucial for host digestion, metabolism, and odor gas production. The results of recent studies have suggested that host microRNAs (miRNAs) can regulate gene expression of the gut microbiota. In the present study, the expression profiles of host-derived miRNAs in the cecal content of two laying hen breeds; Hy-line Gray and Lohmann Pink, which have dissimilar H₂S production, were characterized; and their effects on H₂S production by regulating the expression of gut microbiota-associated genes were demonstrated.

RESULTS

The differential expression of microbial serine O-acetyltransferase, methionine synthase, aspartate aminotransferase, methionine-gamma-lyase, and adenylylsulfate kinase between the two hen breeds resulted in lower H₂S production in the Hy-line hens. The results also revealed the presence of miRNA exosomes in the cecal content of laying hens, and an analysis of potential miRNA-target relationships between 9 differentially expressed miRNAs and 9 differentially expressed microbial genes related to H₂S production identified two methionine synthase genes, Odosp_3416 and BF9343_2953, that are targeted by gga-miR-222a. Interestingly, in vitro fermentation results showed that gga-miR-222a upregulates the expression of these genes, which increased methionine concentrations but decreased H₂S production and soluble sulfide concentrations, indicating the potential of host-derived gga-miR-222a to reduce H₂S emission in laying hens.

CONCLUSION

The findings of the present study reveal both a physiological role by which miRNAs shape the cecal microbiota of laying hens and a strategy to use host miRNAs to manipulate the microbiome and actively express key microbial genes to reduce H₂S emissions and breed environmentally friendly laying hens. Video Abstract.

Physiological and behavioral responses of laying hens exposed to long-term high temperature

The present study was conducted to investigate the impact of a 42 d period of heat stress on laying hens with respect to rectal temperature, body-surface temperature, heart rate, heterophil to lymphocyte ratio (H/L ratio), corticosterone (CORT) in plasma and yolk samples, and video-assessed behaviors. A total of one hundred twenty 56-week-old ISA-brown laying hens were continuously exposed to one of three temperature regimes: optimal (LT; 22 °C), moderate (MT; 27 °C), and high (HT; 32 °C). The relative humidity was maintained at 50% in all treatments. HT vs. MT and LT increased rectal temperature, heart rate, and body-surface temperature on all days (P < 0.05). HT vs. LT raised (P < 0.05) the H/L ratio in blood at day 42 following heat exposure. On the other hand, both HT- and MT-exposed laying hens had higher (P < 0.05) plasma CORT compared with those on LT group only at 28 and 42 d following heat treatment. Yolk CORT was elevated (P < 0.05) in the HT vs. MT and LT groups at 3 and 14 d following heat treatment. Panting and wing elevation were the most relevant behaviors in laying hens exposed to HT vs. MT and LT. The study shows that rectal and body-surface temperature, heart rate, and behavior, but not CORT or H/L ratio, are the reliable indicators for assessing the stress status of laying hens over extended period of heat stress.

Effect of boron supplementation on laying performance of White Leghorn hens fed diet with and without adequate level of calcium

This study was conducted in White Leghorn layers to ascertain the effect of boron (B) supplementation to calcium (Ca) inadequate diet under standard managemental practices. A total of 80 commercial White Leghorn hens, 25 weeks old with a uniform body weight, were randomly assigned to one of the 4 groups of 20 hens/replicates in each dietary group viz., normal calcium (NC)/Ca adequate, low calcium (LC)/Ca-inadequate, normal calcium with 40 ppm B (NCB) and low calcium with 40 ppm B (LCB). Dietary level of Ca was maintained at two levels, 100 (normal) and 90% (inadequate) of the requirement. Supplementation of B at 40 ppm improved (P < 0.01) egg production of layers from third month of trial as compared to un-supplemented group. Feed conversion ratio of layers was positively (P < 0.05) influenced by B supplementation in Ca-inadequate diet. Egg shell thickness of layers was found to be higher (P < 0.001) in groups supplemented 40 ppm B, irrespective of the level of Ca in the diets. Cracked egg production was also significantly (P < 0.01) lower in B-supplemented groups compared to Ca-inadequate group. Boron supplementation improved Ca retention irrespective of dietary Ca level. Low-Ca diet without boron supplementation resulted in lower retention (P < 0.05) of magnesium and boron. It is concluded that supplementation of 40 ppm B to Ca-inadequate diet ameliorated the lower laying performance in layers and confirms the usefulness of B in such abiotic stress situations.

Effect of organic and inorganic dietary selenium supplementation on gene expression in oviduct tissues and Selenoproteins gene expression in Lohman Brown-classic laying hens

Background

The oviduct of a hen provides a conducive environment for egg formation, which needs a large amount of mineral elements from the blood via trans-epithelial permeability. Eggshell is the calcified layer on the outside of an egg that provides protection and is critical for egg quality. However, little is known about the genes or proteins involved in eggshell formation, and their relationship to dietary microminerals. We hypothesized that dietary selenium supplementation in chickens will influence genes involved in eggshell biomineralization, and improve laying hen antioxidant capacity. The objective of this research was to investigate how organic and inorganic dietary selenium supplementation affected mRNA expression of shell gland genes involved in eggshell biomineralization, and selenoproteins gene expression in Lohman Brown-Classic laying hens.

Results

Shell gland (Uterus) and liver tissue samples were collected from hens during the active growth phase of calcification (15–20 h post-ovulation) for RT-PCR analysis. In the oviduct (shell gland and magnum) and liver of laying hens, the relative expression of functional eggshell and hepatic selenoproteins genes was investigated. Results of qPCR confirmed the higher (p < 0.05) mRNA expression of OC-17 and OC-116 in shell gland of organic Se hen compared to inorganic and basal diet treatments. Similarly, dietary Se treatments affected the mRNA expression of OCX-32 and OCX-36 in the shell gland of laying hens. In the magnum, mRNA expression of OC-17 was significantly (p < 0.05) higher in hens fed-bacterial organic, while OC-116 mRNA expression was down-regulated in dietary Se supplemented groups compared to non-Se supplemented hens. Moreover, when compared to sodium selenite, only ADS18 bacterial Se showed significantly (p < 0.05) higher mRNA levels in GPX1, GPX4, DIO1, DIO2 and SELW1, while Se-yeast showed significantly (p < 0.05) higher mRNA levels in TXNRD1 than the non-Se group.

Conclusions

Dietary Se supplementation especially that from a bacterial organic source, improved shell gland and hepatic selenoproteins gene expression in laying hens, indicating that it could be used as a viable alternative source of Se in laying hens. The findings could suggest that organic Se upregulation of shell gland genes and hepatic selenoproteins in laying hens is efficient.

Epigallocatechin-3-gallate Alleviates Vanadium-Induced Reduction of Antioxidant Capacity via Keap1-Nrf2-sMaf Pathway in the Liver, Kidney, and Ovary of Laying Hens

This study evaluated the effect of epigallocatechin-3-gallate (EGCG) alleviating the reduction of antioxidant capacity induced by dietary vanadium (V) in the liver, kidney, and ovary of laying hens. Furthermore, Kelch-like ECH-associated protein 1(Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-small Maf proteins (sMaf) pathway was explored to reveal the molecular mechanism. A total of 768 40-week-old Hyline-Brown laying hens were randomly allocated to 4 groups with 8 pens per group and 24 hens per pen. The experimental groups were as follows: control (basal diet); V15, control + 15 mg/kg V; EGCG150, control + 150 mg/kg EGCG; V15 + EGCG150, V15 + 150 mg/kg EGCG. Our results revealed that dietary EGCG supplementation completely alleviated the V-induced reductions of hen-day egg production, average egg weight, Haugh unit, albumen height, eggshell strength, and eggshell thickness. Dietary EGCG supplementation completely prevented the V-induced reductions of serum follicle-stimulating hormone and luteinizing hormone levels. Besides, dietary EGCG supplementation reversed the V-induced increments of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), creatinine (Cr), and uric acid (UA). In addition, dietary EGCG supplementation partially alleviated the V-induced reductions of the enzyme activities and gene expressions of superoxidative dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GSH-Px). Furthermore, dietary EGCG supplementation partially alleviated the V-induced reductions of Nrf2 and sMaf gene expressions, and the increments of Keap1 gene expression. In summary, EGCG partially alleviated V-induced reduction of antioxidant capacity through Keap1-Nrf2-sMaf pathway in the liver, kidney, and ovary of laying hens.

A novel duplex ddPCR assay for detection and differential diagnosis of Ascaridia galli and Heterakis gallinarum eggs from chickens feces

Since the EU ban on battery cages, many studies have listed Ascaridia galli and Heterakis gallinarum as the most common roundworms in the European laying hen population. A complicating factor is that the eggs of these parasites are almost identical. Thus, lack of molecular diagnostic approaches has driven epidemiological studies to take on necropsy for species discrimination, which is labor and cost intensive. Here, we describe a novel diagnostic tool based on droplet digital PCR for simultaneous identification and absolute quantification of the eggs of both of these ascarids in chickens' droppings using two different genus-specific primer-probe sets targeting the second internal transcribed spacer region (ITS-2) in the nuclear ribosomal (rRNA) gene array. No cross-reaction was observed when different combinations of DNA and species-specific primers and probes were tested. The lowest obtained frequency threshold for the detection of H. gallinarum in the presence of a constant A. galli DNA concentration was determined to be 0.8 %. After validation, we used the assay to analyze field samples collected from several Swedish laying hen farms. Out of 134 samples, 86 (64 %) were positive for A. galli while 11 (8.3 %) samples were positive for H. gallinarum. These samples were initially analyzed with flotation technique for detection of ascarid eggs. The results of the Cohen's kappa indicated substantial agreement (85.8 %) between the two tests. In conclusion, we have validated a novel molecular-based diagnostic tool for quantification and differentiation between intestinal parasites of major importance in chickens with high precision. Although this study focuses on identification of parasites of laying hens, the findings may well have a bearing on all types of chicken production systems. The present study lays the groundwork for future research into epidemiology of these two important chicken parasite species.

Nanoselenium and Selenium Yeast Have Minimal Differences on Egg Production and Se Deposition in Laying Hens

The objective of this study was to compare the effects of nanoselenium (NS) and selenium yeast (SY) on the performance, egg selenium (Se) concentration, and anti-oxidative capacity of hens. A total of 216 Brown Hy-line hens (29-week old) were randomly allocated into three treatments (6 replicate/treatment, 12 hens/replicate). The pre-trial period lasted 7 days, and the experimental period lasted 35 days. Dietary treatments included corn-soybean meal basal diet (containing 0.16 μg Se/g, as control group), and basal diet supplemented with 0.3 mg Se/kg diet (Se was from NS or SY), called as SY group or NS group, respectively. At the end of the experiment, one hen per replicate from each treatment was slaughtered. Liver, spleen, and kidney tissues were sampled for the determination of Se concentrations. The results showed that NS or SY supplement significantly improved feed conversion ratio (P < 0.05), soft broken egg rate (P < 0.05), and the serum T-AOC value (P < 0.05) when compared with control group. Remarkably, the deposition of Se increased significantly (P < 0.05) and equivalently in egg, liver, and kidney of hens supplemented with both NS and SY. Interestingly, SY supplement also enhanced the serum CAT and SOD activities (P < 0.05), NS but not SY significantly reduced serum MDA (P < 0.05), whereas RT-PCR results did not show significant differences in the mRNA levels of antioxidant genes among three groups (P > 0.05). Taken together, dietary supplemented with SY or NS improved the Se deposition in eggs, liver and kidney of laying hens, increased antioxidant activity, and NS supplement had greater Se deposition in the kidney tissue than SY supplement. SY or NS supplement could be considered to be applied for Se-enriched egg production.