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To deeply understanding the impact of peripheral energy level on the development of ovaries during the sexual maturation of chicken, in this study, the ovaries and serum of sexually mature and immature chickens at the same age from different energy level groups were collected, and the proteome and metabolome were detected. The results of ovarian and serum metabolomics revealed that dietary energy levels affected the energy metabolism and fatty acid oxidation of ovary in chicken, including the up-regulated expression of dihydroacetone phosphate and α-linolenic acid in high energy level groups. The results of proteomics showed that peripheral energy levels affected the catecholamine biosynthesis and metabolism in ovary before sexual maturation. The integrating analysis revealed that increased energy flux may influence ovarian development by regulating cholesterol reserves and steroid hormone synthesis in the ovaries. In vitro, the cultivation of chicken primary granulosa cells showed that sterol carrier protein 2 played a role in fatty acid synthesis and metabolism but did not significantly affect progesterone synthesis. Overall, dietary energy levels may be involved in the development of the ovaries during sexual maturation by influencing energy metabolism, biosynthesis of unsaturated fatty acids and steroid hormone within the ovaries.

ABSTRACT: Egg production, regulated by multiple tissues, is among the most important economic traits in poultry. However, current research only focuses on the hypothalamic-pituitary-ovarian axis, ignoring the most important organ for substance metabolism in the body, the liver. Eggs are rich in lipids, proteins, and other nutrients, which are biosynthesized in the liver. Therefore, here the liver was included in the study of the hypothalamic-pituitary axis. This study used hypothalamus (HH_vs_LH), pituitary (HP_vs_LP), liver (HL_vs_LL), and ovary (HO_vs_LO) tissue samples from high- and low-laying Chengkou mountain chickens (CMC) for epihistological, transcriptome and metabolomic analyses aimed at improving the reproductive performance of CMC. The results showed that the liver of the high-laying group was yellowish, the cell boundary was clear, and the lipid droplets were evenly distributed. The ovaries of the high-laying group had a complete sequence of hierarchical follicles, which were rich in yolk. In contrast, the ovaries of the low-laying group were atrophic, except for a few small yellow follicles, and numerous primordial follicles that remained. The transcriptome sequences yielded 167.11 Gb of clean data, containing 28,715 genes. Furthermore, 285, 822, 787, and 1,183 differentially expressed genes (DEG) were identified in HH_vs_LH, HP_vs_LP, HL_vs_LL and HO_vs_LO and the DEGs significantly enriched 77, 163, 170, 171 pathways, respectively. Metabolome sequencing yielded 21,808 peaks containing 4,006 metabolites. The differential metabolite analysis yielded 343 and 682 significantly different metabolites (SDM) that significantly enriched 136 and 87 pathways in the liver and ovaries, respectively. A combined analysis of the transcriptome and metabolome of the liver and ovaries identified “CYP51A1-4α-carboxy-stigmasta7, 24(24(1))-dien-3β-ol” and “ACSS1B-estrone 3-sulfate” and other multiple gene-metabolite pairs. The DEGs in the hypothalamus and pituitary mainly enriched signaling transduction. In contrast, the DEGs and SDMs in the liver and ovaries mainly enriched the substance metabolism pathways: “gap junction”, “extracellular matrix (ECM)-receptor interaction”, “Steroid biosynthesis”, and “Steroid hormone biosynthesis”. These results suggest that the hypothalamic-pituitary axis may affect egg production mainly by regulating lipid metabolism in the liver and ovaries.

ABSTRACT: The development and maturation of follicles are intricately linked to egg production and reproductive performance of chickens. Granulosa cells death directly affects the development and maturation of follicles, thereby impacting the reproductive performance of hens. Ferroptosis is a new type of cell death, it is unknown how it affects the growth and development of chicken follicles. In this study, RNA-seq analysis revealed significant differences in the expression of ferroptosis-related genes between normal follicles and atretic follicles, suggesting a potential role for ferroptosis in follicle growth and development. In addition, we found that ubiquitin-specific protease 13 (USP13) was significantly upregulated in atrophic follicles. Overexpression of USP13 results in depletion of glutathione (GSH), peroxidation of lipids, accumulation of iron, and activation of ferroptosis in chicken granulosa cells. In contrast, USP13 knockdown significantly inhibited ferroptosis events. Mechanistically, USP13 prevents the degradation of autophagy related 7 (ATG7) by deubiquitinating it, thereby enhancing the stability of ATG7 protein and ultimately promoting ferroptosis. In conclusion, this study elucidates the crucial role of the USP13-ATG7 axis in regulating ferroptosis in chicken follicle granulosa cells, thereby presenting a novel avenue for molecular breeding research in chickens.

The Chengkou mountain chicken, a native Chinese poultry breed, holds significant importance in the country’s poultry sector due to its delectable meat and robust stress tolerance. Muscle growth and development are pivotal characteristics in poultry breeding, with muscle fiber development during the embryonic period crucial for determining inherent muscle growth potential. Extensive evidence indicates that non-coding RNAs (ncRNAs) play a regulatory role in muscle growth and development. Among ncRNAs, circular RNAs (circRNAs), characterized by a closed-loop structure, have been shown to modulate biological processes through the regulation of microRNAs (miRNAs). This study seeks to identify and characterize the spatiotemporal-specific expression of circRNAs during embryonic muscle development in Chengkou mountain chicken, and to construct the potential regulatory network of circRNAs-miRNA-mRNAs. The muscle fibers of HE-stained sections became more distinct, and their boundaries were more defined over time. Subsequent RNA sequencing of 12 samples from four periods generated 9,904 novel circRNAs, including 917 differentially expressed circRNAs. The weighted gene co-expression network analysis (WGCNA)-identified circRNA source genes significantly enriched pathways related to cell fraction, cell growth, and muscle fiber growth regulation. Furthermore, a competitive endogenous RNA (ceRNA) network constructed using combined data of present and previous differentially expressed circRNAs, miRNA, and mRNA revealed that several circRNA transcripts regulate MYH1D, MYH1B, CAPZA1, and PERM1 proteins. These findings provide insight into the potential pathways and mechanisms through which circRNAs regulate embryonic muscle development in poultry, a theoretical support for trait improvement in domestic chickens.

This study aimed to investigate the effects of different concentrations of in ovo injection of 25-hydroxycholecalciferol (25(OH)D3) on early growth, immune and tibia development in Daheng broilers. The results showed that 25(OH)D3 can significantly improve the hatchability of broilers and improve body weight (p 0.05). Our data suggested that 25(OH)D3 has positive effects on the early growth, immune, bone development of broiler during the early stage, which is a supplement to improve disease resistance and skeletal development of broilers.

The hypothalamic-pituitary-adrenal (HPA) axis and hypothalamic-pituitary-gonadal (HPG) axis plays a central role in mediating physiological responses related to the reproductive system under any stressful condition. However, the molecular mechanism underlying the effects of stress on physiology still needs to be elucidated. This study demonstrated that increasing the stocking density from 4 to 8 birds/m2 during the laying period decreased the egg production rate of laying ducks by 13.04 − 63.55% and feed intake by 7.40 − 23.44%. Transcriptome analysis between high- and low-feeding-density laying ducks revealed 469, 509, 428 and 210 differentially expressed genes (DEGs) in the hypothalamus, pituitary, ovary and follicular membrane, respectively. Gene ontology (GO) and KEGG enrichment analysis showed that the DEGs in the hypothalamus and pituitary were primarily enriched in the biostimulation and dopamine secretion pathways. The major enrichment pathways in the ovarian and follicular membranes involved lipid metabolism, negative regulation of inflammatory response, and steroid hormone biosynthesis. Among the DEGs in the HPG system, POMC and GnRH1 were identified, which may be manifesting their crucial roles in regulating the stress response and reproduction. Our data showed that a high stocking density as environmental stress negatively affects the reproductive performance in ducks through transcriptional changes in the HPG axis.Highlights Raising the stocking density from 4 to 8 birds/m2 decreased the egg production rate and feed intake in laying ducks. The transcriptome indicated that stocking density affects the stress response of laying ducks through the hypothalamus-pituitary. The stress signals are subsequently transmitted to affect gene expression related to the reproduction process in laying ducks’ ovarian and follicular tissues. The hypothalamic expression of POMC and GnRH1 may play a central role in integrating stress signals and the reproductive processes of laying ducks.

Abstract Background The egg production performance of chickens is affected by many factors, including genetics, nutrition and environmental conditions. These factors all play a role in egg production by affecting the development of follicles. MicroRNAs (miRNAs) are important non-coding RNAs that regulate biological processes by targeting genes or other non-coding RNAs after transcription. In the animal reproduction process, miRNA is known to affect the development and atresia of follicles by regulating apoptosis and autophagy of granulosa cells (GCs). Results In this study, we identified potential miRNAs in the atretic follicles of broody chickens and unatretic follicles of healthy chickens. We identified gga-miR-30a-5p in 50 differentially expressed miRNAs and found that gga-miR-30a-5p played a regulatory role in the development of chicken follicles. The function of miR-30a-5p was explored through the transfection test of miR-30a-5p inhibitor and miR-30a-5p mimics. In the study, we used qPCR, western blot and flow cytometry to detect granulosa cell apoptosis, autophagy and steroid hormone synthesis. Confocal microscopy and transmission electron microscopy are used for the observation of autophagolysosomes. The levels of estradiol (E2), progesterone (P4), malondialdehyde (MDA) and superoxide dismutase (SOD) were detected by ELISA. The results showed that miR-30a-5p showed a negative effect on autophagy and apoptosis of granulosa cells, and also contributed in steroid hormones and reactive oxygen species (ROS) production. In addition, the results obtained from the biosynthesis and dual luciferase experiments showed that Beclin1 was the target gene of miR-30a-5p. The rescue experiment conducted further confirmed that Beclin1 belongs to the miR-30a-5p regulatory pathway. Conclusions In summary, after deep miRNA sequencing on healthy and atretic follicles, the results indicated that miR-30a-5p inhibits granulosa cell death by inhibiting Beclin1.

Studies have shown that prebiotics can affect meat quality; however, the underlying mechanisms remain poorly understood. This study aimed to investigate whether prebiotics affect the flavor of chicken meat via the gut microbiome and metabolome. The gut content was collected from chickens fed with or without prebiotics (galacto-oligosaccharides or xylo-oligosaccharides) and subjected to microbiome and metabolome analyses, whereas transcriptome sequencing was performed using chicken breast. Prebiotic supplementation yielded a slight improvement that was not statistically significant in the growth and production performance of chickens. Moreover, treatment with prebiotics promoted fat synthesis and starch hydrolysis, thus increasing meat flavor by enhancing lipase and α-amylase activity in the blood of broiler chickens. The prebiotics altered the proportions of microbiota in the gut at different levels, especially microbiota in the phyla Bacteroidetes and Firmicutes, such as members of the Alistipes, Bacteroides, and Faecalibacterium genera. Furthermore, the prebiotics altered the content of cecal metabolites related to flavor substances, including 8 types of lysophosphatidylcholine (lysoPC) and 4 types of amino acid. Differentially expressed genes (DEGs) induced by prebiotics were significantly involved in fatty acid accumulation processes, such as lipolysis in adipocytes and the adipocytokine signaling pathway. Changes in gut microbiota were correlated with metabolites, for example, Bacteroidetes and Firmicutes were positively and negatively correlated with lysoPC, respectively. Finally, DEGs interacted with cecal metabolites, especially meat-flavor-related amino acids and their derivatives. The findings of this study integrated and incorporated associations among the gut microbiota, metabolites, and transcriptome, which suggests that prebiotics affect the flavor of chicken meat.

Skeletal muscle, comprising approximately 40% of body mass, is a highly complex and heterogeneous tissue serving a multitude of functions in the organism. Non-coding RNAs (ncRNAs) are known to participate in skeletal muscle development as critical regulators. However, the regulatory mechanisms of ncRNAs on chicken muscle traits are not well understood. In the present study, we collected the leg muscle from male embryos of Tibetan chicken at embryonic (E) 10 and E18 for RNA sequencing. A total of 6,583 differentially expressed mRNAs (DEMs) including 3,055 down-regulated and 3,528 up-regulated were identified in E18. We identified 695 differentially expressed lncRNAs (DELs) (187 down-regulated and 508 up-regulated) and 1,906 differentially expressed circRNAs (DECs) (1,224 down-regulated and 682 up-regulated) in E18. Among the 130 differentially expressed miRNAs (DEMIs), 59 were up-regulated and 71 were down-regulated in E18. Numerous DEMs and target genes for miRNAs/lncRNAs were significantly enriched in the muscle system process and cell cycle. We constructed a miRNA-gene-pathway network by considering target relationships between genes related to skeletal muscle development and miRNAs. A competing endogenous RNA (ceRNA) network was also constructed by integrating competing relationships between DEMs, DELs, and DECs. Several DELs and DECs were predicted to regulate the ADRA1B, ATP2A2, ATP2B1, CACNA1S, CACNB4, MYLK2, and ROCK2 genes. We discovered the crosstalk between the ncRNAs and their competing mRNAs, which provides insights into ceRNA function and mechanisms in the skeletal muscle development of chicken.

ABSTRACT: It is generally accepted the gut microbiota have a profound effect on the nutrition, health, and production in poultry. To deeply understand the gut microbiota composition with the dietary fiber level in broilers, we evaluated the cecal microbiota profiles feeding on different dietary fiber level with alfalfa as additive in Dahen broilers based on 16S rRNA gene sequencing and gas chromatography. As a result, the gut microbiota diversity was greatly accelerated with the dietary fiber level. The dietary fiber stimulated the growth of many intestinal communities such as Rikenellaceae RC9 gut group, Faecalibacterium, Prevotellaceae UCG 001 and Ruminococcaceae UCG 014, and led to an altered microbial function such as Carbohydrate metabolism and Genetic information processing. Meanwhile, we found the genera Anaerofilum and Dielma were significantly correlated with the production of short chain fatty acids (SCFAs). All these results provide a reference for the broilers gut microbiota changes with different dietary fiber level. The key role of the altered microbiota with the dietary fiber may mediate beneficial effects in broiler production, which also reflect the substantial potential of dietary fiber level in poultry.

This study was conducted to evaluate the effects of stocking density on productive performance, egg quality, and antioxidant capacity in laying ducks. A total of 720 20-week-old Jinding laying ducks were randomly assigned to 5 stocking densities (4, 5, 6, 7, and 8 birds/m2) with 8 replicate pens each treatment. The results showed that increasing stocking density linearly increased egg production and egg mass and linearly decreased FCR of laying ducks (P

ABSTRACT: Follicular atresia is an important cause of reproductive decline in egg-laying hens. Therefore, a better understanding of the regulation mechanism of follicle atresia in poultry is an important measure to maintain persistent high egg performance. However, how the role of the regulatory relationship between autophagy and apoptosis in the intrafollicular environment affects the follicular atresia of chickens is remain unclear. The objective of this study was to explore the regulatory molecular mechanisms in regard to follicular atresia. 20 white leghorn layers (32-wk-old) were equally divided into 2 groups. The control group was fed freely, and the experimental group induced follicular atretic by fasting for 5 d. The results showed that the expression of prolactin (PRL) levels was significantly higher in the fasted hens, while the levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were lower. Most importantly, RNA sequencing, qPCR, and Western blotting detected significantly elevated levels of autophagy and apoptosis markers in atresia follicles. Interestingly, we found that fibromodulin (FMOD) levels was significantly lower in follicles from fasted hens and that this molecule had an important regulatory role in autophagy. FMOD silencing significantly promoted autophagy and apoptosis in granulosa cells, resulting in hormonal imbalance. FMOD was found to regulate autophagy via the transforming growth factor beta (TGF-β) signaling pathway. Our results suggest that the increase in autophagy and the imbalance in internal homeostasis cause granulosa cell apoptosis, leading to follicular atresia in the chicken ovary. This finding could provide further insight into broodiness in chicken and provide avenues for further improvements in poultry production.

DNA methylation is a key epigenetic mechanism involved in embryonic muscle development and plays an important role in early muscle development. In this study, we sought to investigate the effects of genome-wide DNA methylation by combining the expression profiles of the chicken embryonic muscle. Genome-wide DNA methylation maps and transcriptomes of muscle tissues collected from different embryonic development points (E7, E11, E17, and D1) were used for whole-genome bisulfite sequencing (WGBS) and RNA sequencing, respectively. We found that the differentially methylated genes (DMGs) were significantly associated with muscle organ development, regulation of skeletal muscle satellite cell proliferation, and actin filament depolymerization. Furthermore, genes TBX1, MEF2D, SPEG, CFL2, and TWF2 were strongly correlated with the methylation-caused expression switch. Therefore, we chose the CFL2 gene to explore its function in skeletal muscle satellite cells, and the in vitro experiments showed that CFL2 acts as a negative regulator of chicken skeletal muscle satellite cell proliferation and can induce cell apoptosis. These results provide valuable data for future genome and epigenome studies of chicken skeletal muscle and may help reveal the molecular mechanisms of potential economic traits.

Abstract Background There are hundreds of phenotypically distinguishable domestic chicken breeds or lines with highly specialized traits worldwide, which provide a unique opportunity to illustrate how selection shapes patterns of genetic variation. There are many local chicken breeds in China. Results Here, we provide a population genome landscape of genetic variations in 86 domestic chickens representing 10 phenotypically diverse breeds. Genome-wide analysis indicated that sex chromosomes have less genetic diversity and are under stronger selection than autosomes during domestication and local adaptation. We found an evidence of admixture between Tibetan chickens and other domestic population. We further identified strong signatures of selection affecting genomic regions that harbor genes underlying economic traits (typically related to feathers, skin color, growth, reproduction and aggressiveness) and local adaptation (to high altitude). By comparing the genomes of the Tibetan and lowland fowls, we identified genes associated with high-altitude adaptation in Tibetan chickens were mainly involved in energy metabolism, body size maintenance and available food sources. Conclusions The work provides crucial insights into the distinct evolutionary scenarios occurring under artificial selection for agricultural production and under natural selection for success at high altitudes in chicken. Several genes were identified as candidates for chicken economic traits and other phenotypic traits.

Indoor environmental control is usually applied in poultry farming to ensure optimum growth conditions for birds. However, these control methods represent a considerable share of total energy consumption, and the trend of applying new equipment in the future for precision livestock farming would further increase energy demand, resulting in an increase in greenhouse gas emissions and management costs. Therefore, to ensure optimum efficiency of both energy use and livestock productivity, a customized hourly model was developed in the present study to interpret and analyze the electronically collected data. The modules for estimating indoor gas concentrations were incorporated into the present model, as this has not been properly considered in previous studies. A validation test was performed in a manure-belt layer house using sensors and meters to measure the indoor environmental parameters and energy consumption. The predicted results, including indoor temperature, relative humidity, carbon dioxide and ammonia concentrations, showed good agreement with the measured data, indicating a similar overall trend with acceptable discrepancies. Moreover, the corresponding differences between the measured and simulated energy consumption for heating, tunnel ventilation and base ventilation were 13.7, 7.5, and 0.1%, respectively. The total energy demand estimated by the model showed a limited discrepancy of approximately 10.6% compared with that measured in reality. Although human factors, including inspection, cleaning, vaccination, etc., were not included in the model, the validation results still suggested that the customized model was able to accurately predict the indoor environment and overall energy consumption during poultry farming. The validated model provides a tool for poultry producers to optimize production planning and management strategies, increase the production rate of unit energy consumption and achieve precision livestock farming from an energy consumption standpoint.

As a ubiquitous heavy metal, cadmium (Cd) is highly toxic to various organs. However, the effects and molecular mechanism of Cd toxicity in the chicken heart remain largely unknown. The goal of our study was to investigate the cardiac injury in chickens' exposure to Cd. We detected the levels of oxidative stress–related molecules in the Cd-induced chicken heart, and assessed the histopathological changes by hematoxylin and eosin staining. RNA sequencing was performed to identify differentially expressed mRNAs between the Cd-induced group and control group. The expression of candidate genes involved in oxidative stress was certified by quantitative reverse transcription PCR. Our results showed that the expression of glutathione, peroxidase, and superoxide dismutase was significantly decreased and malondialdehyde was increased in the heart of chickens by Cd induction. The disorderly arranged cardiomyocytes, swelled and enlarged cells, partial cardiomyocyte necrosis, blurred morphological structure, and notable inflammatory cell infiltration were observed in the Cd-induced chicken heart. RNA sequencing identified 23 upregulated and 11 downregulated mRNAs in the heart tissues of the chicken in the Cd-induced group, and functional pathways indicated that they were associated with oxidative stress. Moreover, CREM, DUSP8, and ITGA11 expressions were significantly reduced, whereas LAMA1 expression was induced in heart tissue of chickens by Cd treatment. Overall, our findings revealed that oxidative stress and pathological changes in the chicken heart could be triggered by Cd. The mRNA transcriptional profiles identified differentially expressed genes in the chicken heart by Cd induction, revealing oxidative stress–related key genes and enhancing our understanding of Cd toxicity in the chicken heart.

Background MicroRNAs (miRNAs) exist widely and are involved in multiple biological processes in ducks, whereas the regulatory mechanism of miRNAs in egg laying of ducks has remained unclear. This study aims to reveal key miRNAs involved in the regulation of egg production in duck ovaries. Methods High-throughput sequencing was performed on four egg-type duck ovaries and four egg-meat-type duck ovaries at the start of the egg-laying stage. Quantitative reverse transcription PCR (qRT-PCR) validation was performed on differentially expressed miRNAs (DE miRNAs). Gene network of DEmiRNA-mRNA-pathway was constructed by Cytoscape. Results A total of 251 know miRNAs and 1,972 novel miRNAs were obtained from whole clean reads. Among the known miRNAs, we identified 21 DEmiRNAs, including eight down-regulated and 13 up-regulated miRNAs in egg-type ducks compared with egg-meat-type ducks. Among the novel miRNAs, we identified 70 DEmiRNAs, including 58 down-regulated and 12 up-regulated in egg-type ducks compared with egg-meat-type ducks. The expression patterns of four miRNAs were verified by qRT-PCR. The DEmiRNAs were involved in the function of response to folic acid and the pathway of valine, leucine and isoleucine degradation. Specific target genes of DEmiRNAs enrichment was found in some egg-laying regulation pathways, such as dopaminergic synapse, ovarian steroidogenesis and oocyte meiosis. The DEmiRNA-mRNA-pathway network including three DEmiRNAs, nine mRNAs and 11 pathways. apl-miR-194-5p and apl-miR-215-5p may be potential key miRNAs in regulating egg laying. Conclusions This study provided miRNAs profiles in ducks about egg laying and establish a theoretical basis for subsequent selection or modification of duck phenotypes at the molecular level.

Previous studies reported that the Myoz1 gene plays a crucial role in signal transduction and muscle fibre type differentiation. This finding suggests that the Myoz1 gene is a potential candidate for affecting carcase and meat quality traits in animals. Therefore, this study aimed to detect genetic variations in Avian and Yellow Bantam chickens and to evaluate the effects of these variations on economically important carcase and meat-quality traits. Expression analysis using quantitative real-time PCR indicated that Myoz1 was broadly expressed in all four studied tissues (liver, heart, breast muscle and leg muscle). Expression of Myoz1 was significantly higher in both leg muscle and breast muscle compared to the liver and heart. Then, using direct sequencing, a total of five single nucleotide polymorphisms (SNPs) were identified within the Myoz1 gene in two breeds of chickens. These breeds included three non-synonymous SNPs (SNP1: g. 16022512 G > T, SNP3: g. 16022560 C > T and SNP5: g.16023903 A > G) corresponding to A103S, H119Y and S189G, respectively. Statistical analyses indicated that SNP2 (g. 16022529 T > C), SNP3, SNP4 (g.16023878 A > C) and SNP5 significantly influenced some carcase and meat quality traits. Meanwhile, we did not find any association between the constructed haplotype and carcase traits in the Avian nor Yellow Bantam chickens. In conclusion, SNPs in the Myoz1 gene could be used for marker-assisted selection in chicken breeding.

The main advantage of having livestock, for example, the laying hens, in a controlled environment is that the optimum growth conditions can be achieved with accuracy. The indoor air temperature, humidity, gases concentration, etc., would significantly affect the animal performance, thus should be maintained within an acceptable range. In order to achieve the goals of precision poultry farming, various models have been developed by researchers all over the world to estimate the hourly indoor environmental parameters so as to provide decision suggestions. However, a key parameter of hourly manure area in the poultry house was missing in the literature to predict the ammonia emission using the recently developed mechanistic model. Therefore, in order to fill the gap of the understanding of hourly manure coverage proportion and area on the manure belt, experimental measurements were performed in the present study using laying hens from 10 weeks age to 30 weeks age. For each test, six polypropylene (pp) plates were applied to collect the manure dropped by the birds every hour, and photographs of the plates were taken at the same time using a pre-fixed camera. Binary images were then produced based on the color pictures to determine the object coverage proportion. It was demonstrated that for laying hens of stocking density around 14 birds/m2, the manure coverage proportion at the 24th hour after the most recent manure removal was about 60%, while the value was approximately 82% at the 48th hour. Meanwhile, for laying hens at different ages, the hourly increment of manure coverage proportion showed a similar pattern with four distinct stages within 48 h. The statistical analyses demonstrated no significant correlation between the hourly increment of manure weight and the hourly increment of manure coverage proportion. Finally, prediction models for estimating the hourly manure coverage proportion on the manure belt in typical laying hen houses were provided.

The aim of the study was to compere the effects of using air energy heat pump, flue heating and water heating as brood heating system on brood production of yellow-feathered broilers. In the experiment, three heating methods were used to heat chicks, and the parameters such as heating time, temperature uniformity, concentration of poisonous and harmful gases in the house, chick weight gain, mortality rate and production benefit were compered and analyzed. The results showed as follows: 1. There was no significant difference in NH3 and H2S concentration among the three groups (P > 0.05). The CO2 concentration in the flue group was significantly higher than that in the other two groups (P < 0.01), and there was no significant difference in CO2 concentration between the other two groups (P >0.05). 2. The body weight of chickens in the flue group at 30 days of age was the lowest, which was significantly different from that in the other two groups (P < 0.01); The air energy heat pump group had significant difference with coal fired boiler group (P < 0.05), the uniformity and survival rate of flue group were the lowest, and the air energy heat pump group had the best; 3. The temperature rise of honeycomb flue was the slowest, the temperature distribution uniformity was the worst, and the cost was the highest; The heating rate of coal-fired boiler was faster than that of flue, and the temperature distribution uniformity was better, and the cost was lower. The heating rate of air energy heat pump was the fastest, and the temperature distribution uniformity was better, and the operating cost was the lowest. 4. The air energy heat pump group has higher investment in the early stage, better use effect, better production performance of brood, long service life and lower brood cost.

Peroxisome proliferator activated receptor-alpha (PPARα) and Egl nine homolog 3 (EGLN3) play critical roles in facilitating the adaptation to a hypoxic environment. However, the relationship between EGLN3 and PPARα variants and hypoxic adaptation remains poorly understood in Tibetan chickens. To better understand the effects of genetic variation, we sequenced exons of PPARα and EGLN3 in 138 Lowland chickens (LC) from 7 breeds that were located in Emei, Miyi, Shimian, Wanyuan, Pengxian, and Muchuan in the Sichuan province, and Wenchang in the Hainan province (altitudes for these locations are below 1800 meters). Total 166 Tibetan chickens (TC) from 7 subpopulations that were located in Shigatse, Lhoka, Lhasa, Garze, Aba, Diqing and Yushu in the Tibetan area were also sequenced (altitudes greater than 2700 meters). One single-nucleotide polymorphism (rs316017491, C > T) was identified in EGLN3 and was shared by TC and LC with no significant difference for allele frequencies between them (P > 0.05). Six single-nucleotide polymorphisms (SNP1, A29410G; SNP2, rs13886097; SNP3, T29467C; SNP4, rs735915170; SNP5, rs736599044; and SNP6, rs740077421) including one non-synonymous mutation (SNP2, T > C) were identified in PPARα. This is the first report of SNP1 and SNP3. There was a difference between TC and LC for allele frequencies (P

Tibetan chickens living at high altitudes show specific adaptations to high-altitude conditions, but the epigenetic modifications associated with these adaptations have not been characterized.We investigated the genome-wide DNA methylation patterns in Tibetan chicken blood by using whole genome bisulfite sequencing. Generally, Tibetan chickens exhibited analogous methylation patterns to that of lowland chickens. A total of 3.92% of genomic cytosines were methylcytosines and 51.22% of cytosines in CG contexts were methylated, which was less than those in lowland chicken (55.69%). Moreover, the base adjacent to the methylcytosines of mCHGs in Tibetan chickens had a preference for T, which was different from that in lowland chickens. In Tibetan chickens, the methylation levels in the promoter were relatively low, while the gene body was also maintained in a hypomethylated state. DNA methylation levels in regions upstream of the transcription start site of genes were negatively correlated with the level of gene expression, and DNA methylation of gene body regions was also negatively related to gene expression.We generated the genome-wide DNA methylation patterns in Tibetan chickens and our results will be helpful for future epigenetic studies related to adaptations to high-altitude conditions.

Due to the increasing demand for producing chickens with high meat quality, there is a need to determine its mode of action on chicken meat quality traits across a wider age spectrum. In this study, five groups of 200 male Da-Heng meat type birds were reared until slaughter age of 60, 90, 120, 150, 180 days old and breast muscle performance, meat quality traits, and myofiber characteristics were evaluated. The larger body weight and breast weight of chicken are based on larger myofiber diameter and area, less myofiber density for the older birds than younger birds. There was an age effect on all meat quality traits of chicken breast muscle (p < 0.05). Older chickens often presented a higher pH, lower drip loss, higher shear force, darker, and redder breast meat. The correlation coefficients showed that myofiber characteristics played an important role in breast pH values, drip loss, and meat color (p < 0.05). Besides, significant correlations were also found between meat quality traits (p < 0.05). Further studies are needed to explore the biochemical character and potential molecular mechanism of chicken breast muscle to determine the factors that causes these age-related differences in meat quality in the current study.

The calpain system is ubiquitous in cells, mainly comprising calpains and calpain inhibitors, and is a widespread calcium-dependent cysteine protease in organisms that is involved in many cellular processes such as muscle degradation in vivo and affects the tenderness of meat after animal slaughter. The study found 128 DEGs that probably regulated tenderness traits were selected from 16 significantly enriched GO terms by transcriptome sequencing analysis, and found that the developmental changes in the expression levels of the CAPNI gene in the pectoral and leg muscles were significantly positively correlated (P<0.05) with the cumulative growth values of live weight and comb weight. The developmental changes in the expression levels of the CAST gene in the pectoral and leg muscles were not significantly correlated with the cumulative growth values of live weight and comb weight. Our results helped demonstrate the potential molecular mechanisms of tenderness in chickens and provide valuable information for chicken breeding. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of different concentrations of in ovo injection of 25-hydroxycholecalciferol (25(OH)D3) on early growth, immune and tibia development in Daheng broilers. The results showed that 25(OH)D3 can significantly improve the hatchability of broilers and improve body weight (p < 0.05). The low concentration of 25(OH)D3 (8 μg/mL) not only significantly increased tibial fresh weight, tibial length, tibial diameter, thymus and liver weight and immune organ index (p < 0.05), but also significantly increased the content of bone metabolism-related factors OC and CaBP in serum and the expression levels of OC in the liver (p < 0.05). However, a high concentration of 25 (OH)D3 group (16 μg/mL) significantly increased bursa of Fabricius weight and immune organ index (p < 0.05), the content of immune factor IL-2, IFN-γ and TLR15 in serum and the expression level of IFN-γ and TLR15 in the spleen (p < 0.05). Furthermore, the content of ash, calcium and phosphorus in the tibia was negatively correlated with the expression level of OC and positively correlated with the expression level of ALP (p > 0.05). Our data suggested that 25(OH)D3 has positive effects on the early growth, immune, bone development of broiler during the early stage, which is a supplement to improve disease resistance and skeletal development of broilers. [ABSTRACT FROM AUTHOR]