Egg-laying Performance Research Articles

Transcriptome profiling reveals SLC5A5 regulates chicken ovarian follicle granulosa cell proliferation, apoptosis, and steroid hormone synthesis

The egg-laying performance of hens holds significant economic importance within the poultry industry. Broody inheritance of the parent stock of chickens can result in poor options for the improvement of egg production, and is a phenomenon influenced by multiple genetic factors. However, few studies have been conducted to delineate the molecular mechanism of ovarian regression in brooding chickens. Here, we explored the pivotal genes responsible for the regulation of ovarian follicles in laying hens, using RNA-sequencing analysis on the small ovarian follicles from broody and laying chickens. Sequencing data analysis revealed the differential expression of 200 genes, with a predominant enrichment in biological processes related to cell activation and metabolism. Among these genes, we focused on solute carrier family 5 member 5 (SLC5A5), which exhibited markedly higher RNA expression levels in follicles from laying compared with broody chickens. Subsequent cellular function studies with knockdown of SLC5A5 in chicken ovarian follicle granulosa cells (GCs) led to the down-regulation of genes associated with cell proliferation and steroid hormone synthesis, and concurrent promotion of gene expression linked to apoptosis. These findings indicated that SLC5A5 deficiency led to the inhibition of proliferation, steroid hormone synthesis and secretion, and promotion of apoptosis in chicken GCs. Our study demonstrated a pivotal role for SLC5A5 in the development and function of chicken GCs, shedding light on its potential significance in the broader context of chicken ovarian follicle development, and providing a prospective target to improve the egg-laying performance of chickens via molecular marker-assisted breeding technology.

Transcriptome-wide m6A methylation profiling of Wuhua yellow-feathered chicken ovary revealed regulatory pathways underlying sexual maturation and low egg-laying performance.

RNA N6-melthyladenosine (m6A) can play an important role in regulation of various biological processes. Chicken ovary development is closely related to egg laying performance, which is a process primarily controlled by complex gene regulations. In this study, transcriptome-wide m6A methylation of the Wuhua yellow-feathered chicken ovaries before and after sexual maturation was profiled to identify the potential molecular mechanisms underlying chicken ovary development. The results indicated that m6A levels of mRNAs were altered dramatically during sexual maturity. A total of 1,476 differential m6A peaks were found between these two stages with 662 significantly upregulated methylation peaks and 814 downregulated methylation peaks after sexual maturation. A positive correlation was observed between the m6A peaks and gene expression levels, indicating that m6A may play an important role in regulation of chicken ovary development. Functional enrichment analysis indicated that apoptosis related pathways could be the key molecular regulatory pathway underlying the poor reproductive performance of Wuhua yellow-feathered chicken. Overall, the various pathways and corresponding candidate genes identified here could be useful to facilitate molecular design breeding for improving egg production performance in Chinese local chicken breed, and it might also contribute to the genetic resource protection of valuable avian species.

Effect of papaya (Carica papaya) seed as phytogenic feed additives on egg performance, egg quality and blood serum biochemical constituents of layer hens.

Supplementing poultry diets with certain natural phytogenic additives has positive impacts on performance parameters like feed intake, egg production and quality of layer hens. The study aimed to examine how supplementing papaya seed as phytogenic feed additive (PFA) to the diets of layer chickens affected their egg production, quality and blood serum biochemical parameters. One hundred twenty 28-week-old Bovans brown laying hens were randomly assigned to one of four treatments with varying levels of papaya seed supplementation at 0g/kg (T1), 5g/kg (T2), 10g/kg (T3) and 15g/kg (T4) in a complete randomized design. Layer chickens supplemented with 0.5% (T2), 1% (T3) and 1.5% (T4) papaya seed as a PFA had significantly (p<0.05) improved dry matter intake, egg production%, egg mass and feed conversion. On the other hand, papaya seed supplementation decreased (p<0.05) the bodyweight gain of laying hens. Papaya seed supplementation significantly (p<0.05) increased egg weight, length, width, yolk height and yolk colour compared to the control group. Serum total protein on T4 and liver enzyme of alkaline phosphatase on T3 were significantly greater (p<0.05) than in the control group. However, there were no significant differences (p>0.05) in serum albumin, glucose, total cholesterol, triglyceride and aspartate aminotransferase levels among treatments laying hens. Papaya seed can be a potential candidate as a PFA at 5-15g/kg of the basal diet to improve egg-laying performance and quality without deteriorating effect.

Dynamic mRNA expression during chicken ovarian follicle development.

Ovarian follicle development is a complex and well-orchestrated biological process of great economic significance for poultry production. Specifically, understanding the molecular mechanisms underlying follicular development is essential for high-efficiency follicular development can benefit the entire industry. In addition, domestic egg-laying hens often spontaneously develop ovarian cancer, providing an opportunity to study the genetic, biochemical, and environmental risk factors associated with the development of this cancer. Here, we provide high-quality RNA sequencing data for chicken follicular granulosa cells across 10 developmental stages, which resulted in a total of 204.57 Gb of clean sequencing data (6.82 Gb on average per sample). We also performed gene expression, time-series, and functional enrichment analyses across the 10 developmental stages. Our study revealed that SWF (small while follicle), F1 (F1 hierarchical follicles), and POFs (postovulatory follicles) best represent the transcriptional changes associated with the prehierarchical, preovulatory, and postovulatory stages, respectively. We found that the preovulatory stage F1 showed the greatest divergence in gene expression from the POF stage. Our research lays a foundation for further elucidation of egg-laying performance of chicken and human ovarian disease.

Integrating genomics and transcriptomics to identify candidate genes for high egg production in Wulong geese (Anser cygnoides orientalis)

BackgroundWulong geese (Anser cygnoides orientalis) are known for their excellent egg-laying performance. However, they show considerable population differences in egg-laying behavior. This study combined genome-wide selection signal analysis with transcriptome analysis (RNA-seq) to identify the genes related to high egg production in Wulong geese.ResultsA total of 132 selected genomic regions were screened using genome-wide selection signal analysis, and 130 genes related to high egg production were annotated in these regions. These selected genes were enriched in pathways related to egg production, including oocyte meiosis, the estrogen signaling pathway, the oxytocin signaling pathway, and progesterone-mediated oocyte maturation. Furthermore, a total of 890 differentially expressed genes (DEGs), including 340 up-regulated and 550 down-regulated genes, were identified by RNA-seq. Two genes — GCG and FAP — were common to the list of selected genes and DEGs. A non-synonymous single nucleotide polymorphism was identified in an exon of FAP.ConclusionsBased on genome-wide selection signal analysis and transcriptome data, GCG and FAP were identified as candidate genes associated with high egg production in Wulong geese. These findings could promote the breeding of Wulong geese with high egg production abilities and provide a theoretical basis for exploring the mechanisms of reproductive regulation in poultry.

Phosphoproteome Reveals Extracellular Regulated Protein Kinase Phosphorylation Mediated by Mitogen-Activated Protein Kinase Kinase-Regulating Granulosa Cell Apoptosis in Broody Geese.

Geese have strong brooding abilities, which severely affect their egg-laying performance. Phosphorylation is widely involved in regulating reproductive activities, but its role in goose brooding behavior is unclear. In this study, we investigated differences in the phosphoprotein composition of ovarian tissue between laying and brooding geese. Brooding geese exhibited ovarian and follicular atrophy, as well as significant oxidative stress and granulosa cell apoptosis. We identified 578 highly phosphorylated proteins and 281 lowly phosphorylated proteins, and a KEGG pathway analysis showed that these differentially phosphorylated proteins were mainly involved in cell apoptosis, adhesion junctions, and other signaling pathways related to goose brooding behavior. The extracellular regulated protein kinase (ERK)-B-Cell Lymphoma 2(BCL2) signaling pathway was identified as playing an important role in regulating cell apoptosis. The phosphorylation levels of ERK proteins were significantly lower in brooding geese than in laying geese, and the expression of mitogen-activated protein kinase kinase (MEK) was downregulated. Overexpression of MEK led to a significant increase in ERK phosphorylation and BCL2 transcription in H2O2-induced granulosa cells (p < 0.05), partially rescuing cell death. Conversely, granulosa cells receiving MEK siRNA exhibited the opposite trend. In conclusion, geese experience significant oxidative stress and granulosa cell apoptosis during brooding, with downregulated MEK expression, decreased phosphorylation of ERK protein, and inhibited expression of BCL2.

The improving effect of soybean isoflavones on ovarian function in older laying hens

Emerging evidence suggests an association between estrogen levels and reduced egg-laying performance as the layer became old. Since soy isoflavones (SF) have estrogen-mimic effects, whether it can enhance production performance and ovarian function of older layers is still not known. A total of 160 Lohmann pink layers (66-wk-old) were used in a 2×2 factorial design, which included 2 egg-laying levels [low (76.89 ± 1.65%; LOW) and normal (84.96 ± 1.01%; NOR)] and 2 different dietary groups [0 mg/kg SF, 20 mg/kg SF] were used. The results showed the NOR group had higher egg-laying rate, egg mass, and feed efficiency during the all phases (P(laying) < 0.05). The unqualified egg rate was lower in NOR group (9-12 wk, 1-12 wk) (P(laying) < 0.05). Dietary supplementation with SF increased the egg-laying rate and feed efficiency (5-8 wk, 9-12 wk, 1-12 wk), increased egg mass (9-12 wk, 1-12 wk) (P(SF) < 0.05). The NOR layers presented higher eggshell quality (redness, yellowness, brightness, eggshell ratio) at 12 wk (P(laying) < 0.05). Eggshell quality was found to be improved by SF (eggshell strength and eggshell thickness), egg albumen quality (higher albumen height and Haugh unit) at 12 wk (P(SF) < 0.05). Supplementing with SF led to an increase in eggshell strength in LOW group (P(laying*SF) < 0.05). The higher serum lever of glucose (GLU) and lower serum lever of follicle stimulating hormone (FSH) were in NOR group (P(laying) < 0.05). Supplementing SF in diets increased serum of estradiol (E2) and insulin-like growth factors-1 (IGF-1), decreased serum of FSH (P(SF) < 0.05). The NOR layers presented lower estrogen receptor α (ERα), estrogen receptor β (ERβ), B lymphoma 2 associated X protein (Bax), cytochrome c (Cytc), interleukin 6 (IL-6), caspase3, caspase9, IKKα, P50, and P65 expression in the ovary (P(laying) < 0.05). Dietary SF supplementation decreased the anti-Müllerian hormone receptor (AMHR), Bax, caspase3, caspase9, Cytc, IL-6, IKKα, P50, P65 expression in the ovary (P(SF) < 0.05). These findings indicated that layers with NOR group had higher production performance, egg quality, and ovarian function, while dietary supplementation with SF improved production performance and ovarian function by reducing inflammation and apoptosis-related genes expression in ovary.

Polymorphism, Genetic Effect, and Association with Egg-Laying Performance of Chahua Chickens Matrix Metalloproteinases 13 Promoter.

Matrix metalloproteinases are a group of proteases involved in the regulation of ovarian follicular development and ovulation. Among the different MMPs, MMP13 is known to play an important role in reproduction. Therefore, this study aimed to screen the molecular genetic markers of the MMP13 gene that affect the egg-laying performance of Chahua chickens. Polymerase chain reaction (PCR) and sequencing were performed in the 5' regulation region of the MMP13 gene to detect loci significantly related to the egg-laying performance of Chahua chickens. A double fluorescence reporting system, quantitative reverse transcription PCR (RT-qPCR), and Western blotting were used to study whether gene expression was regulated by identified sites, providing a theoretical basis to improve egg production in Chahua chickens. The results revealed six single nucleotide polymorphisms (SNPs; A-1887T, T-1889C, A-1890T, T-2252C, T-2329C, and C-2360A) in the promoter region of the MMP13 gene. Further analysis revealed that hens with T-1890-C-1889-T-1887/T-1890-C-1889-T-1887 (mutant type, MT) had an earlier age at first egg (AFE) than hens with A-1890-T-1889-A-1887/A-1890-T-1889-A-1887 (wild type, WT; p < 0.05). RT-qPCR showed that the relative expression level of the MMP13 gene in the ovarian tissues of individuals with the mutation was higher than that of individuals with the wild gene (p < 0.05). Western blot results confirmed higher levels of the MMP13 protein in MT ovaries compared to those in WT ovaries. Thus, this study suggests that mutation sites on the MMP13 promoter may affect gene expression. In conclusion, the MMP13 gene in Chahua chickens may be significant for egg-laying performance, and the polymorphism in its promoter region could be used as a molecular marker to improve egg-laying performance.

Effect of feed particle size on growth and egg-laying parameters of Japanese quail (Coturnix japonica) in Côte d’Ivoire

In Côte d’Ivoire, the quail breeding is confronted with the lack of food specific to the species. Thus, in the south-east of this country, an experimental study was conducted at the ISMOREL farm in the sub-prefecture of Adiaké. This study, which aims to improve the productivity of day-to-day farms, focused on the grain size of the feed. From grower (GD) and layer (LD) diets, 5 experimental diets have been manufactured. There are: LD 5 with a particle size of 5 mm, LD 3 and GD 3 with a particle size of 3 mm as well as LD 2 and GD 2 with a particle size of 2 mm. The growth parameters related to 750 two-week-old unsexed subjects weighing 49.67 ± 0.17 g on average. For egg-laying, 300 female quails were used at 6-week-old. The results showed an influence of the 2 mm grain size (LD 2 and GD 2) on parameters such as feed intake (186.96 ± 4.73 g and 153.46 ± 5.33 g), average live weight (142.37 ± 1.76 g and 155.85 ± 1.85 g), the average daily gain (4.29 ± 1.22 g/d and 4.74 ± 1.25 g/d), the age of first egg laid (49.33 ± 0.58 d and 46.33 ± 1.26 d) and egg-laying rate (67.24 ± 30.97% and 74.12 ± 34.03%). At the end of this study, it appears that the 2 mm particle size induces better growth and egg-laying performance in Japanese quail.

Yolk precursor synthesis and deposition in hierarchical follicles and effect on egg production performance of hens

Egg production of hens is related to ovarian follicles development. The hierarchical follicle development accompanies the deposition of a large amount of yolk precursor. The aim of this study was to illustrate the effects of strain and age on yolk deposition and egg production. The experiment compared yolk synthesis, transport, and deposition in 3 groups of hens: one of a high-yield commercial hybrid laying breed (Jinghong No.1) in 2 stages (35 wk and 75 wk; JH35, JH75) and one of Chinese native breed (Lueyang Black-Boned chicken) at 35 wk (LY35). The results showed that the number of hierarchical follicles in JH35 and JH75 was significantly more than in LY35. At the same time, the yolk weight of the LY35 and JH75 was significantly higher than that of JH35. The expression of apolipoprotein A1 and apolipoprotein B genes in the liver of JH35 was higher than that of JH75. The expression of the very low-density lipoprotein receptor gene in the JH75 ovary was higher than that of the other 2 groups. The plasma concentrations of very low-density lipoprotein and vitellogenin were no significant difference among groups. The yolk deposition in hierarchical follicles based on the fat-soluble dyes measurement meant that the rate of yolk deposition of LY35 was lower than the other 2 groups. In most cases, the yolk deposition of JH75 was higher than that of the other groups, but the process showed greater fluctuation over time. These results meant that the rate and stability of yolk deposition played an essential role in affecting egg performance. In summary, both strain and age were related to egg production, but the 2 factors might impact yolk deposition and egg-laying performance differently. The egg performance may be affected by both yolk precursor synthesis and deposition for different strains, but it may be affected by yolk precursor deposition for the old laying hens.

Impact of Cannabis Seed Incorporation in Layer Diet on Productive Performance and Egg Quality Traits.

The production of nonindustrial cannabis is highly developed in the Moroccan Rif region; however, local farmers consider hemp seeds which are rich in omega 3 and tocopherols, only as by-products of cannabis cultivation with low market value. The local ecotype is considered to be a plant with a cannabinoid content of more than 0.4%. So, the objective of this research is to investigate how the incorporation of this local hemp seed affects productive performance and egg quality traits. The experiment is conducted to evaluate the effects of hemp seed (HS) incorporation on hen laying performance and physical egg quality at three levels: 10% (HS-10% group), 20% (HS-20% group), and 30% (HS-30% group). Ninety-six Lohmann Brown classic laying hens were randomly assigned to a control group and three feed treatments. The sampling was taken after the 28-week rearing period (peak egg laying). Throughout the experiment, low-rate HS inclusion (HS-10%) showed no significant differences in egg-laying performance (p > 0.05). However, the high incorporation rates of HS (20% and 30%) negatively affected the egg-laying performance (84-94% and 80-86%, respectively). The albumen quality was also improved by the HS inclusion, where the highest values of the Haugh unit were recorded, ranging between 68.69 and 73.91 for the HS-30% groups. The results also show that HS inclusion and duration influence significantly the yolk color (p < 0.001). The yellow intensity decreases with HS incorporation and aging, from a dark yellow (b ∗ = 38.63 for the control group) to a very pale yellow (b ∗ = 26.29 for HS 30% group). Based on these findings, we can conclude that the incorporation of nonindustrial Moroccan cannabis seeds (ecotype Beldiya) at low rate in the diet of laying hens does not alter the laying performance or the quality of the egg; therefore, they could be used in poultry feeding as an alternative constituent to partially replace high-cost imported ingredients, such as corn and soybeans.

Transcriptomic analysis of ovarian follicles uncovers the crucial genes relevant to follicle selection and preovulatory hierarchy in hens.

Follicle selection and preovulatory hierarchy of hen ovaries were important stages of follicle development and crucially determining egg-laying performance. The selected follicles with a higher expression level of follicle-stimulating hormone receptor (FSHR) mRNA that facilitates response to FSH, and rapidly develops into preovulatory follicles with distinctive characteristics of granulosa cells (GCs) proliferation and differentiation. Identification of the key genes involved in these developmental events is helpful for elucidation of the molecular mechanism underlying egg-laying traits in chicken and other domestic fowl. Herein, the comparative transcriptomic analysis of ovarian prehierarchical follicles before selection (BSF), follicles at selection stage (ASF), and hierarchical follicles (HF) were implemented in the Jilin Black chicken (JB) and Lohmann Brown layer (LB) with the divergences in their egg-laying performance by RNA-sequencing. The results showed that nine deferentially expressed genes (DEGs), including STMN4, FABP3, ROBO2, RSPO4, and DMRT1 were revealed between follicles BSF and ASF; and seventeen DEGs, such as SLC6A15, SLITRK3, PRKG2 and TMC3 were mined between ASF and HF. These two group DEGs being co-expressed between BSF and ASF, and between ASF and HF were compared and substantiated in the JB and LB layers, respectively. Furthermore, 10 signaling pathways, such as cAMP signaling, PPAR signaling pathway, AMPK(Adenosine 5'-monophosphate (AMP)-activated protein kinase) pathway, and estrogen signaling pathway were also identified. Moreover, the roles of two representative candidates ROBO2 and PRKG2 genes presented as downregulated mRNA expression pattern in the transcriptomic profiles were further verified in vitro. The results demonstrated that downregulation of ROBO2 or PRKG2 significantly increased the expression levels of FSHR mRNA and protein with the boosted expression of CCND1, STAR, and BCL-2, whereas remarkably inhibited the expression of Caspase-3, consequently, brought about the decrease of GC apoptosis in the ovarian follicles, but increase of GC proliferation and differentiation serving as the hallmarks for follicle selection. It indicated that ROBO2 and PRKG2 may play indispensable roles in follicle selection and preovulatory hierarchy of hen ovaries separately. Our findings provided a comparative transcriptomic evidence for clarifying the molecular mechanism of the follicle development underlying egg-laying traits in chicken.

Improvement in ovarian function following fecal microbiota transplantation from high-laying rate breeders

The underlying mechanism between the gut microbiota and reproductive function is not yet well-known. This study was conducted to investigate the effect of the administration of fecal microbiota transplantation (FMT) from highly laying rate donors on the cecal microbiota, intestinal health and ovarian function in broiler breeders. A total of 60 broiler breeders (53 wk of age) were selected by their laying rate [high (HP, 90.67 ± 0.69%; n=10) and low (LP, 70.23 ± 0.87%; n=20)]. The LP breeders were then be transplanted with fecal microbiota from HP hens (FMTHP; n=10) or the same dosage of PBS (FMTCON; n=10) for 28 d. The results revealed that FMT from HP donors increased egg-laying rate and serum hormone levels [17β-estradiol (E2), anti-Müller hormone], also decreased proinflammatory cytokine levels (interleukin-6, interleukin-8, tumor necrosis factor-α) of LP breeders (P < 0.05). The FMTHP group breeders had higher villus height, villus height/crypt depth ratio, and upregulated mRNA expression of jejunum barrier-related gene (ZO-2 and mucin-2) and estrogen, follicle-stimulating hormone (FSH) and anti-Müller hormone (AMH) receptor genes (ESR1, ESR2, FSHR, AMHR) (P < 0.05) than FMTCON group. FMT from HP donors led to higher mRNA expression of Bcl2 and sirtuin1 (SIRT1), while it downregulated the proapoptotic genes (Bax, caspase-3, caspase-8, and caspase-9) mRNA expressions in ovary compared with the FMTCON breeders (P < 0.05), and this pattern was also observed in HP donors. Also, HP breeder had higher observed_species and alpha-diversity indexes (Chao1 and ACE) than FMTCON group, while FMTHP can increase observed_species and alpha-diversity indexes (Chao1 and ACE) than FMTCON group (P < 0.05). The bacteria enrichment of Firmicutes (phylum), Bacteroidetes (phylum), Lactobacillus (genus), Enterococcus (genus), and Bacteroides (genus) were increased by FMTHP treatment. The genera Butyricicoccus, Enterococcus, and Lactobacillus were positively correlated with egg-laying rate. Therefore, cecal microbiomes of breeders with high egg-laying performance have more diverse activities, which may be related to the metabolism and health of the host; and FMT from high-yield donors can increase the hormone secretion, intestinal health, and ovarian function to improve egg-laying performance and the SIRT1-related apoptosis and cytokine signaling pathway were involved in this process.

Evolutionary analysis and functional characterization reveal the role of the insulin-like growth factor system in a diversified selection of chickens (Gallus gallus)

The insulin-like growth factor (IGF) system plays an indispensable role in embryonic and postnatal development in mammals. However, the effects of the system on growth, carcass, and egg-laying traits, and diversified selection have not been systematically studied in chickens. In the present study, firstly the composition and gene structures of the chicken IGF system were investigated using phylogenetic tree and conserved synteny analysis. Then the effects of the genetic variations in the IGF system genes on breeding of specialized varieties were explored by principal component analysis. In addition, the spatiotemporal expression properties of the genes in this system were analyzed by RT-qPCR and the functions of the genes in egg production performance and growth were explored by association study. Moreover, the effects of IGF-binding proteins 3 (IGFBP3) on skeletal muscle development in chicken were investigated by cell cycle analysis, 5-ethynyl-2'-deoxyuridine (EdU) and Cell Counting Kit-8 (CCK-8) assays. The results showed that the chicken IGF system included 13 members which could be classified into 3 groups based on their amino acid sequences: IGF binding proteins 1 to 5 and 7 (IGFBP1-5 and 7) belonged to the first group; IGF 1 and 2 (IGF1 and IGF2), and IGF 1 and 2 receptor (IGF1R and IGF2R) belonged to the second group; and IGF2 binding proteins 1-3 (IGF2BP1-3) belonged to the third group. The IGF2BP1 and 3, and IGFBP2, 3, and 7 genes likely contributed more to the formation of both the specialized meat-type and egg-type lines, whereas IGFBP1 and 5 likely contributed more to the formation of the egg-type lines. The SNPs in the IGF2BP3 and IGFBP2 and 5 genes were significantly associated with egg number, and SNPs in the IGFBP3 promoter region were significantly associated with body weight, breast muscle weight and leg muscle weight. The IGFBP3 inhibited proliferation but promoted differentiation of chicken primary myoblasts (CPMs). These results provide insights into the roles of the IGF system in the diversified selection of chickens. The SNPs associated with egg-laying performance, growth, and carcass traits could be used as genetic markers for breeding selection of chickens in the future.

Effects of melittin on laying performance and intestinal barrier function of quails

To study the effects of melittin on egg-laying performance and intestinal barrier of quails, 240 quails (aged 70 d) were randomly divided into 4 groups with 6 replicates (10 quails per replicate). They were fed with basal diet (group B), basal diet+0.08 g/kg melittin (group BA1), basal diet+0.12 g/kg melittin (group BA2) and basal diet+0.16 g/kg melittin (group BA3). The experiment lasted for 21 days. The eggs were collected every day. At the end of the experiment, duodenal, jejunal, and ileal tissues were collected, and the cecal contents were sampled. Intestinal antioxidant index, barrier function, and intestinal flora were analyzed. The results showed that the addition of melittin significantly increased the laying rate and average egg weight. Addition of melittin significantly increased the antioxidant function, mechanical barrier, immune barrier, and the villus height to crypt depth ratio of small intestine. Addition of melittin had no significant effect on the α and β diversity of cecal flora, but significantly increased the abundance of Bacteroidales at family level and genus level. Bioinformatics analysis of cecal content showed significant increase in COG functional category of cytoskeleton, and significant decrease in RNA processing and modification in group BA2. KEGG functional analysis showed significant decrease in steroid biosynthesis, caffeine metabolism, and cytochrome P450 pathways in group BA2. In conclusion, addition of 0.12 g/kg melittin to feed improved the laying performance and the intestinal antioxidant capacity and barrier function of quails but had no significant effect on the composition and structure of cecal microbial community. This study provides experimental data and theoretical basis for the application of melittin as a new quail feed additive.

Transcriptomic analysis of the thyroid and ovarian stroma reveals key pathways and potential candidate genes associated with egg production in ducks

The importance of thyroid-related genes has been repeatedly mentioned in the transcriptome studies of poultry with different laying performance, yet there are few systematic studies to unravel the regulatory mechanisms of the thyroid-ovary axis in the poultry egg production process. In this study, we compared the transcriptome profiles in the thyroid and ovarian stroma between high egg production (GP) and low egg production (DP) ducks, and then revealed the pathways and candidate genes involved in the process. We identified 1,114 and 733 differentially expressed genes (DEGs) in the thyroid and ovarian stroma, separately. The Gene Ontology (GO) analysis showed that a total of 504 and 189 GO terms were identified in the thyroid and ovarian stroma (P < 0.05). Three common GO terms were identified from the top 5 GO terms with the highest significant level in two tissues, including extracellular space, calcium ion binding, and integral component of plasma membrane. The enrichment analysis of the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that 15 and 14 KEGG pathways were significantly (P < 0.05) enriched in the thyroid and ovarian stroma, respectively. And, there were 8 common pathways, including neuroactive ligand-receptor interaction, calcium signaling pathway, ECM-receptor interaction, PPAR signaling pathway, melanogenesis, wnt signaling pathway, vascular smooth muscle contraction, and cytokine-cytokine receptor interaction. Notably, the neuroactive ligand-receptor interaction pathway was the most significantly enriched by the DEGs both in the thyroid and ovarian stroma. The interaction among DEGs enriched in the neuroactive ligand-receptor interaction and ECM-receptor interaction suggested that the thyroid may regulate ovarian development by these genes. Through integrated analysis of the protein-protein interaction (PPI) network and KEGG pathway maps, 9 key DEGs (PTH, THBS2, THBS4, CD36, ADIPOQ, ACSL6, PRKAA2, CRH, and PCK1) were identified, which could play crucial roles in the thyroid to regulate ovarian function and then affect egg-laying performance between GP and DP. This study serves as a basis to explore the molecular mechanism of the thyroid affecting ovarian function and egg production in female ducks and may help to identify molecular markers that can be used for duck genetic selection.

Construction of low intestinal bacteria model and its effect on laying performance and immune function of laying hens

The objective of this study was to establish a low-bacteria intestinal model in chickens, and then to investigate the characteristics involving in immune function and intestinal environment of this model. A total of 180 twenty-one-week-old Hy-line gray layers were randomly allocated into 2 treatment groups. Hens were fed with a basic diet (Control), or an antibiotic combination diet (ABS) for 5 weeks. Results showed that the total bacteria in the ileal chyme were significantly dropped after ABS treatment. Compared with the Control group, the genus-level bacteria such as Romboutsia, Enterococcus, and Aeriscardovia were reduced in the ileal chyme of the ABS group (P < 0.05). In addition, the relative abundance of Lactobacillus_delbrueckii, Lactobacillus_aviarius, Lactobacillus_gasseri, and Lactobacillus_agilis in the ileal chyme were also descended (P < 0.05). However, Lactobacillus_coleohominis, Lactobacillus_salivarius, and Lolium_perenne were elevated in the ABS group (P < 0.05). Beyond that, ABS treatment decreased the levels of interleukin-10 (IL-10) and β-defensin 1 in the serum, as well as the number of goblet cells in the ileal villi (P < 0.05). Additionally, the genes mRNA levels of the ileum such as Mucin2, Toll-like receptors 4 (TLR4), Myeloid differentiation factor 88 (MYD88), NF-κB, IL-1β, Interferon-gama (IFN-γ), IL-4 and the ratio of IFN-γ to IL-4 were also down-regulated in the ABS group (P < 0.05). In addition, there were no significant changes about egg production rate and egg quality in the ABS group. In conclusion, dietary supplemental antibiotic combination for 5 weeks could establish a low intestinal bacteria model of hens. The establishment of a low intestinal bacteria model did not affect the egg-laying performance, while caused immune suppression in laying hens.

Transcriptome Analysis of the Ovaries of Taihe Black-Bone Silky Fowls at Different Egg-Laying Stages.

The poor egg-laying performance and short peak egg-laying period restrict the economic benefits of enterprises relating to the Taihe black-bone silky fowl. Ovaries are the main organ for egg production in poultry. Unlike that of mammals, the spawning mechanism of poultry has rarely been reported. As a prominent local breed in China, the reproductive performance of Taihe black-bone silky fowls is in urgent need of development and exploitation. To further explore the egg-laying regulation mechanism in the different periods of Taihe black-bone silky fowls, the ovarian tissues from 12 chickens were randomly selected for transcriptome analysis, and 4 chickens in each of the three periods (i.e., the pre-laying period (102 days old, Pre), peak laying period (203 days old, Peak), and late laying period (394 days old, Late)). A total of 12 gene libraries were constructed, and a total of 9897 differential expression genes (DEGs) were identified from three comparisons; the late vs. peak stage had 509 DEGs, the pre vs. late stage had 5467 DEGs, and the pre vs. peak stage had 3921 DEGs (pre-stage: pre-egg-laying period (102 days old), peak-stage: peak egg-laying period (203 days old), and late-stage: late egg-laying period (394 days old)). In each of the two comparisons, 174, 84, and 2752 differentially co-expressed genes were obtained, respectively, and 43 differentially co-expressed genes were obtained in the three comparisons. Through the analysis of the differential genes, we identified some important genes and pathways that would affect reproductive performance and ovarian development. The differential genes were LPAR3, AvBD1, SMOC1, IGFBP1, ADCY8, GDF9, PTK2B, PGR, and CD44, and the important signaling pathways included proteolysis, extracellular matrices, vascular smooth muscle contraction, the NOD-like receptor signaling pathway and the phagosome. Through the analysis of the FPKM (Fragments Per Kilobase of exon model per Million mapped fragments) values of the genes, we screened three peak egg-laying period-specific expressed genes: IHH, INHA, and CYP19A1. The twelve genes and five signaling pathways mentioned above have rarely been reported in poultry ovary studies, and our study provides a scientific basis for the improvement of the reproductive performance in Taihe black-bone silky fowls.

Cecum microbiome and metabolism characteristics of Silky Fowl and White Leghorn chicken in late laying stages.

Cecal microflora plays a key role in the production performance and immune function of chickens. White Leghorn (WL) is a well-known commercial layer line chicken with high egg production rate. In contrast, Silky Fowl (SF), a Chinese native chicken variety, has a low egg production rate, but good immune performance. This study analyzed the composition of cecal microbiota, metabolism, and gene expression in intestinal tissue of these varieties and the correlations among them. Significant differences were observed in the cecal microbes: Bacteroides was significantly enriched in WL, whereas Veillonellaceae and Parabacteroides were significantly enriched in SF. Carbohydrate biosynthesis and metabolism pathways were significantly upregulated in WL cecum, which might provide more energy to the host, leading to persistently high levels of egg production. The higher Parabacteroides abundance in SF increased volicitin content, enhanced α-linolenic acid metabolism, and significantly negatively correlated with metabolites of propanoate metabolism and carbohydrate metabolism. Genes related to lipid metabolism, immunity, and melanogenesis were significantly upregulated in the SF cecum, regulating lipid metabolism, and participating in the immune response, while genes related to glucose metabolism and bile acid metabolism were expressed at higher levels in WL, benefiting energy support. This study provided a mechanism for intestinal microorganisms and metabolic pathways to regulate chicken egg-laying performance and immunity.

Association analysis and expression level of ACE polymorphisms with egg-laying trait in Taihang chicken

The number of egg-laying is an important indicator of reproduction performance in poultry breeding. To investigate the relationship between the function of Angiotensin-converting enzyme (ACE) and egg-laying performance of Taihang chicken, the mRNA and protein expression and single nucleotide polymorphism (SNP) of ACE were detected. Analysis of ACE bioinformatics and association analysis of polymorphisms were then performed. The polymorphisms analysis of ACE showed that three SNP loci (g.5066812A>C, g.5080076G>A, and g.5072728A>G) were detected in 800 Taihang chickens with egg-laying records. Association analysis of egg-laying found that ACE g.5066812A>C mutation was significantly associated with the egg-laying performance of Taihang chickens (P < 0.05), and the individuals with the g.5066812A>C mutation showed significantly increasing egg-laying. The mRNA expression was significantly higher in individuals with the AA genotype mutation than those with the AC and CC genotypes (P < 0.01), and the expression of ACE protein levels was consistent with the mRNA expression. Bioinformatics analysis indicated that these mutations affected the secondary and tertiary structure of ACE. This study provides new insights into ACE affecting chicken egg production and some basis for improving the egg production rate of Taihang chickens.