Project description:BackgroundEggshell breaking strength is critical to reduce egg breaking rate and avoid economic loss. The process of eggshell calcification initiates with the egg entering the uterus and lasts about 18 h. It follows a temporal sequence corresponding to the initiation, growth and termination periods of shell calcification. During each period of shell calcification, our study investigated the differences of gonadal hormones and uterine transcriptome in laying hens producing a high or low breaking strength shell.Results60 Hy-line Brown laying hens were selected and divided into two groups according to eggshell breaking strength. Eggshell breaking strength of 44.57 ± 0.91 N and 26.68 ± 0.38 N were considered to be the high strength group (HS) and low strength group (LS), respectively. The results showed that mammillary thickness and mammillary knob width of eggshells were significantly lower in the HS. Serum progesterone (P4) and 1,25-dihydroxy vitamin D3 [1,25-(OH)2D3] were significantly higher in the HS compared to the LS during the initiation period of calcification. Serum estradiol (E2) and calcium did not change significantly. All factors mentioned above had no significant differences in the growth and termination periods of calcification. The relative expression of CaBP-D28k and PMCA 1b were not significantly different between HS and LS. The relative expression of NCX1 was significantly higher in HS compared to LS. Moreover, 1777 differentially expressed genes (DEGs) were obtained in the initiation period of calcification. However, few DEGs were identified in the growth or termination periods of calcification. 30 DEGs were selected as candidate genes involved in eggshell calcification during the initiation period of calcification by the analysis of GO terms and KEGG pathways.ConclusionsOur study concluded that mammillary thickness and mammillary knob width of the HS were significantly lower than LS. P4 and 1,25-(OH)2D3 were significantly higher in the initiation period of HS. They may impact initial calcification when the mammillary layer is formed. The initiation period of calcification determined eggshell strength rather than the growth or termination periods. We inferred P4 or 1,25-(OH)2D3 may effect the ultrastructure of the mammillary layer by regulating the expression of uterine genes.

Project description:Purpose: With the advent of Next-generation sequencing (NGS), several novel genes/proteins and cellular pathways in wide variety of tissues has been discovered. The aim of this study are to perform uterine transcriptome profiling (RNA-seq) to determine differently expressed genes in laying and non-laying hens and to further validate the expression of candidate genes using real-time quantitative reverse transcription polymerase chain reaction (qRT–PCR) in laying, non-laying and molting hens. Methods: Uterine mRNA profiles of 35-60 weeks-old laying and non-laying hens, three each, were generated with NextSeq 500 sequencer in single-end mode with a read length of 1x76 bp. Raw sequencing reads were cleaned and trimmmed with Prinseq tool and good reads were aligned against the chicken reference gemone (Galgal 5.0) in Array Studio. Differential gene expression analysis was performed by the DESeq2 algorithm as implemented in Array Studio. The genes with at least two-fold change (FC) and Benjamini and Hochberg q-value < 0.05 were called differentially expressed. Results: Using an optimized data analysis workflow, we mapped about 32 million reads from layers and 28 million reads from non-layers to the chicken genome. A total of 19,152 gene transcripts were annotated from Ensembl alignment which represents 50.24% of the chicken genome assembly. Differential gene expression analysis showed 616 were differentially expressed between layer and non-layer hens. 229 DEGs were significantly up-regulated and 286 were significantly down-regulated in the laying hens when compared to the non-laying hens. Twelve candiate genes, linked to calcium remodeling, were identified by gene function analysis and validated using qPCR. MEPE, CALCB, OTOP2, STC2 and ATP2C2 were confirmed to be highly expressed in laying hens as compared to molting and non-laying hens. RNA-seq and qPCR data for relative gene expression were highly correlated (R2 =0.99). Conclusions: Our study reports the expression of four novel genes that are speculated to transport calcium ions across the uterine epithellium for eggshell mineralization. These genes can be used as quantitative basis of selecting hens with an improved eggshell quality.

Project description:In this study, RNA-Seq technology was adopted to investigate the differences in expression profiles of the hepatic lipid metabolism-related genes and the associated pathways between juvenile and laying hens. RNA-Seq analysis was carried out to estimate total RNA harvested from the liver of juvenile hens (n = 3) and laying hens (n = 3). Compared with juvenile hens, 2574 differentially expressed (DE) genes (1487 down and 1087 up) with P â¤ 0.05 were obtained, and 955 of these genes were significantly DE (SDE) at a false discovery rate (FDR) of 0.05 and fold-change â¥ 2 in laying hens. There were 198 SDE novel genes (107 down-regulated and 91 up-regulated) (FDR â¤ 0.05) that were obtained from the transcriptome, and most of them were highly expressed. Moreover, 332 SDE isoforms were identified. Gene Ontology (GO) enrichment and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis showed that SDE genes were significantly associated with steroid biosynthesis, PPAR signaling pathway, biosynthesis of unsaturated fatty acids, glycerophospholipid metabolism, three amino acid pathways, and pyruvate metabolism (P â¤ 0.05). The top significantly enriched GO terms included lipid biosynthesis, cholesterol and sterol metabolic, and oxidation reduction suggesting the principal lipogenesis in the liver of laying hens. This study suggests that the major changes at the level of transcriptome in laying hen liver are closely related to fat metabolism. Some highly differentially expressed uncharacterized novel genes and alternative splicing isoforms detected might also take part in lipid metabolism, though it needs investigation. Therefore, this study provides valuable information of mRNA of chicken liver, and deeper functional investigations on the mRNAs could help explore or provide new insights into molecular networks of lipid metabolism in chicken liver. The liver expression profile of juvenile hens and laying hens were generated by RNA-seq.

Project description:BackgroundFloor eggs, which are defined as eggs that hens lay off-nest, are a major issue in cage-free layer poultry systems. They create additional work for farmers because they must be collected by hand. They are also usually soiled or broken, which results in economic losses. Nonetheless, knowledge about the genetics of nesting behavior is limited. The aim of this study was to estimate genetic parameters for traits related to nest preference for laying and to time spent in the nests used for laying (laying duration).MethodsTwo pure lines of laying hens were studied: 927 Rhode Island Red and 980 White Leghorn. Electronic nests were used to record the nesting behavior of these hens in floor pens from 24 to 64 weeks of age. Nest preference was studied based on the mean distance between nests used for laying and the percentage of nests used for laying. Laying duration was studied based on mean laying duration, mean duration in the nest before laying, and mean duration in the nest after laying. Genetic parameters were estimated for each line using a restricted maximum-likelihood method applied to a pedigree-based multi-trait animal model.ResultsEstimates of genetic parameters were similar for the two lines. Estimates of heritability ranged from 0.18 to 0.37 for nest preference traits and from 0.54 to 0.70 for laying duration traits. Estimates of genetic correlations of these traits with clutch number or mean oviposition time were favorable. Positive genetic correlations were estimated between nest preference and laying rate in the nests or nest acceptance for laying (+ 0.06 to + 0.37).ConclusionsThese results show that genetics influences traits related to nest preference and laying duration. Selecting hens that have no preference for particular nests and spend little time laying in the nests could help optimize nest use, reduce their occupation rate, and thus decrease the incidence of floor eggs in cage-free systems. Genetic correlations of these traits with other traits of interest related to hen welfare and egg quality have yet to be estimated.

Project description:The intense selection of chickens for production traits, such as egg laying, is thought to cause undesirable side effects and changes in behavior. Trade-offs resulting from energy expenditure in productivity may influence other traits: in order to sustain energetic costs for high egg production, energy expenditure may be redirected away from specific behavioral traits. For example, such energetic trade-offs may change the hens' cognitive abilities. Therefore, we hypothesized highly productive laying hens to show reduced learning performance in comparison to moderate productive lines. We examined the learning ability of four chicken lines that differed in laying performance (200 versus 300 eggs/year) and phylogenetic origin (brown/white layer; respectively, within performance). In total 61 hens were tested in semi-automated Skinner boxes in a three-phase learning paradigm (initial learning, reversal learning, extinction). To measure the hens' learning performance within each phase, we compared the number of active decisions needed to fulfill a learning criteria (80% correct choices for learning, 70% no responses at extinction) using linear models. Differences between the proportions of hens per line that reached criterion on each phase of the learning tasks were analyzed by using a Kaplan-Meier (KM) survival analysis. A greater proportion of high productive hens achieved the learning criteria on each phase compared to less productive hens (Chi2 3 = 8.25, p = 0.041). Furthermore, high productive hens accomplished the learning criteria after fewer active decisions in the initial phase (p = 0.012) and in extinction (p = 0.004) compared to the less selected lines. Phylogenetic origin was associated with differences in learning in extinction. Our results contradict our hypothesis and indicate that the selection for productivity traits has led to changes in learning behavior and the high productive laying hens possessed a better learning strategy compared to moderate productive hens in a feeding-rewarding context. This better performance may be a response to constraints resulting from high selection as it may enable these hens to efficiently acquire additional energy resources. Underlying mechanisms for this may be directly related to differences in neuronal structure or indirectly to foraging strategies and changes in personality traits such as fearfulness and sociality.

			Action	DRS
	SRR8692160_1.fastq.gz	Fastqsanger.gz
	SRR8692160_2.fastq.gz	Fastqsanger.gz
	SRR8692161_1.fastq.gz	Fastqsanger.gz
	SRR8692161_2.fastq.gz	Fastqsanger.gz
	SRR8692152_1.fastq.gz	Fastqsanger.gz

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Uterine transcriptome of hens laying hard or weak-shell eggs

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