1. Korat (KR) chicken is a new meat-type chicken breed established with the purpose of developing Small and Micro Community Enterprise Production. This slow-growing chicken has been recognised for ...its good texture and flavour, but its low feed efficiency is associated with high cost of production which can hamper the development of local production. This has highlighted the importance of studying the trade-off between feed efficiency and meat quality in KR chicken.
2. This study investigated the phenotypic correlations between feed efficiency, growth performance, and meat quality in KR chicken. Individual body weight and feed intake were recorded weekly for 75 male KR chickens for the calculation of feed conversion ratio (FCR) and residual feed intake (RFI). The growth curve was modelled by Gompertz function and meat quality evaluated at 10 weeks of age, through the measurement of pH (pH
u
), water-holding capacity (WHC) and drip loss (DL) in breast and thigh muscle.
3. Faster growth rate at young age appeared favourable, regarding feed efficiency, since a moderate negative correlation was found between FCR and initial growth rate. Chickens with a higher initial growth and maturation rates were characterised by lower water-holding capacity in meat. This was not associated with acidic meat, since a higher speed of growth (especially in the first weeks) was positively associated with final pH in breast meat. Relationships between RFI and meat quality traits appeared to be weak. While better FCR could be achieved by increased initial growth rate, this seemed to negatively impact water-holding capacity of the meat.
4. RFI appeared as an interesting alternative as a compromise between FCR and meat quality.
The chicken eggshell is a natural mechanical barrier to protect egg components from physical damage and microbial penetration. Its integrity and strength is critical for the development of the embryo ...or to ensure for consumers a table egg free of pathogens. This study compared global gene expression in laying hen uterus in the presence or absence of shell calcification in order to characterize gene products involved in the supply of minerals and / or the shell biomineralization process.
Microarrays were used to identify a repertoire of 302 over-expressed genes during shell calcification. GO terms enrichment was performed to provide a global interpretation of the functions of the over-expressed genes, and revealed that the most over-represented proteins are related to reproductive functions. Our analysis identified 16 gene products encoding proteins involved in mineral supply, and allowed updating of the general model describing uterine ion transporters during eggshell calcification. A list of 57 proteins potentially secreted into the uterine fluid to be active in the mineralization process was also established. They were classified according to their potential functions (biomineralization, proteoglycans, molecular chaperone, antimicrobials and proteases/antiproteases).
Our study provides detailed descriptions of genes and corresponding proteins over-expressed when the shell is mineralizing. Some of these proteins involved in the supply of minerals and influencing the shell fabric to protect the egg contents are potentially useful biological markers for the genetic improvement of eggshell quality.
Selection programs have enabled broiler chickens to gain muscle mass without similar enlargement of the cardiovascular and respiratory systems that are essential for thermoregulatory efficiency. ...Meat-type chickens cope with high ambient temperature by reducing feed intake and growth during chronic and moderate heat exposure. In case of acute heat exposure, a dramatic increase in morbidity and mortality can occur. In order to alleviate heat stress in the long term, research has recently focused on early thermal manipulation. Aimed at stimulation of long-term thermotolerance, the thermal manipulation of embryos is a method based on fine tuning of incubation conditions, taking into account the level and duration of increases in temperature and relative humidity during a critical period of embryogenesis. The consequences of thermal manipulation on the performance and meat quality of broiler chickens have been explored to ensure the potential application of this strategy. The physiological basis of the method is the induction of epigenetic and metabolic mechanisms that control body temperature in the long term. Early thermal manipulation can enhance poultry resistance to environmental changes without much effect on growth performance. This review presents the main strategies of early heat exposure and the physiological concepts on which these methods were based. The cellular mechanisms potentially underlying the adaptive response are discussed as well as the potential interest of thermal manipulation of embryos for poultry production.
The broiler industry is facing an increasing prevalence of breast myopathies, such as white striping (WS) and wooden breast (WB), and the precise aetiology of these occurrences remains poorly ...understood. To progress our understanding of the structural changes and molecular pathways involved in these myopathies, a transcriptomic analysis was performed using an 8 × 60 K Agilent chicken microarray and histological study. The study used pectoralis major muscles from three groups: slow-growing animals (n = 8), fast-growing animals visually free from defects (n = 8), or severely affected by both WS and WB (n = 8). In addition, a weighted correlation network analysis was performed to investigate the relationship between modules of co-expressed genes and histological traits. Functional analysis suggested that selection for fast growing and breast meat yield has progressively led to conditions favouring metabolic shifts towards alternative catabolic pathways to produce energy, leading to an adaptive response to oxidative stress and the first signs of inflammatory, regeneration and fibrosis processes. All these processes are intensified in muscles affected by severe myopathies, in which new mechanisms related to cellular defences and remodelling seem also activated. Furthermore, our study opens new perspectives for myopathy diagnosis by highlighting fine histological phenotypes and genes whose expression was strongly correlated with defects.
Because the cost of cereals is unstable and represents a large part of production charges for meat-type chicken, there is an urge to formulate alternative diets from more cost-effective feedstuff. We ...have recently shown that meat-type chicken source is prone to adapt to dietary starch substitution with fat and fiber. The aim of this study was to better understand the molecular mechanisms of this adaptation to changes in dietary energy sources through the fine characterization of transcriptomic changes occurring in three major metabolic tissues - liver, adipose tissue and muscle - as well as in circulating blood cells.
We revealed the fine-tuned regulation of many hepatic genes encoding key enzymes driving glycogenesis and de novo fatty acid synthesis pathways and of some genes participating in oxidation. Among the genes expressed upon consumption of a high-fat, high-fiber diet, we highlighted CPT1A, which encodes a key enzyme in the regulation of fatty acid oxidation. Conversely, the repression of lipogenic genes by the high-fat diet was clearly associated with the down-regulation of SREBF1 transcripts but was not associated with the transcript regulation of MLXIPL and NR1H3, which are both transcription factors. This result suggests a pivotal role for SREBF1 in lipogenesis regulation in response to a decrease in dietary starch and an increase in dietary PUFA. Other prospective regulators of de novo hepatic lipogenesis were suggested, such as PPARD, JUN, TADA2A and KAT2B, the last two genes belonging to the lysine acetyl transferase (KAT) complex family regulating histone and non-histone protein acetylation. Hepatic glycogenic genes were also down-regulated in chickens fed a high-fat, high-fiber diet compared to those in chickens fed a starch-based diet. No significant dietary-associated variations in gene expression profiles was observed in the other studied tissues, suggesting that the liver mainly contributed to the adaptation of birds to changes in energy source and nutrients in their diets, at least at the transcriptional level. Moreover, we showed that PUFA deposition observed in the different tissues may not rely on transcriptional changes.
We showed the major role of the liver, at the gene expression level, in the adaptive response of chicken to dietary starch substitution with fat and fiber.
ABSTRACT
Slow-growing chicken lines are valuable genetic resources for the development of well-perceived alternative free-range production. While there is no constraint on increasing growth rate, ...breeding programs have to evolve in order to include new traits improving the positioning of such lines in the growing market for parts and processed products. In this study, we used dense genotyping to fine map QTL for chicken growth, body composition, and meat quality traits in view of developing new tools for selection of a slow-growing line. The dataset included a total of 836 birds (10 sires, 87 dams, 739 descendants) and 40,203 SNP. QTL for the 15 traits analyzed were detected by 3 different methods, i.e., linkage and linkage disequilibrium haplotype-based analysis (LDLA), family-based single marker association (FASTA), and Bayesian multi-marker regression (Bayes Cπ). After filtering for QTL redundancy, we found 16, 16, and 9 QTL when using the FASTA, LDLA, and Bayes Cπ methods, respectively, with a threshold of 2.49 × 10−5 for FASTA and LDLA, and a Bayes factor of 150 for the Bayes Cπ analysis. They comprised 17 QTL for body weight, 9 QTL for body composition, and 15 QTL for breast meat quality or behavior at slaughter. The 3 methods agreed in the detection of highly significant QTL such as that detected on GGA24 for body weight at 3, 6, and 9 wk, and the 2 QTL detected on GGA17 and GGA18 for breast meat yield. Several significant QTL were also detected for the different components of breast meat quality. This study provided new locations for investigation in order to improve our understanding of the genetic architecture of growth, carcass composition, and meat quality in the chicken and to develop molecular tools for the selection of these traits in a slow-growing line.
Gene expression profiling has become a tool of choice to study pathological or developmental questions but in most cases the material is scarce and requires sample amplification. Two main procedures ...have been used: in vitro transcription (IVT) and polymerase chain reaction (PCR), the former known as linear and the latter as exponential. Previous reports identified enzymatic pitfalls in PCR and IVT protocols; however the possible differences between the sequences affected by these amplification defaults were only rarely explored.
Screening a bovine cDNA array dedicated to embryonic stages with embryonic (n = 3) and somatic tissues (n = 2), we proceeded to moderate amplifications starting from 1 mug of total RNA (global PCR or IVT one round). Whatever the tissue, 16% of the probes were involved in deviating gene expressions due to amplification defaults. These distortions were likely due to the molecular features of the affected sequences (position within a gene, GC content, hairpin number) but also to the relative abundance of these transcripts within the tissues. These deviating genes mainly encoded housekeeping genes from physiological or cellular processes (70%) and constituted 2 subsets which did not overlap (molecular features, signal intensities, gene ID). However, the differential expressions identified between embryonic stages were both reliable (minor intersect with biased expressions) and relevant (biologically validated). In addition, the relative expression levels of those genes were biologically similar between amplified and unamplified samples.
Conversely to the most recent reports which challenged the use of intense amplification procedures on minute amounts of RNA, we chose moderate PCR and IVT amplifications for our gene profiling study. Conclusively, it appeared that systematic biases arose even with moderate amplification procedures, independently of (i) the sample used: brain, ovary or embryos, (ii) the enzymatic properties initially inferred (exponential or linear) and (iii) the preliminary optimization of the protocols. Moreover the use of an in-house developed array, small-sized but well suited to the tissues we worked with, was of real interest for the search of differential expressions.
Gallus gallus eggshell is a bioceramic composed of 95% calcium carbonate in calcitic form and 3.5% extracellular organic matrix. The calcification process occurs in the uterine fluid where ...biomineralization follows a temporal sequence corresponding to the initiation, growth and termination stages of crystal growth. Eggshell texture and its ultrastructure are regulated by organic matrix proteins, which control mineralization process and influence the eggshell biomechanical properties. We performed proteomic qualitative analyses and identified 308 uterine fluid proteins. Quantitative analysis showed differential abundances at the three stages of shell biomineralization for 64 of them. Cluster analysis revealed a first group of proteins related to mineralization and mainly present at the onset of calcification including OVOT, OVAL, OC-17, and two novel calcium binding proteins (EDIL3, MFGE8). A second group of proteins mainly present at the initiation and termination of shell formation was potentially involved in the regulation of the activity of the uterine fluid proteins (e.g. molecular chaperones, folding proteins, proteases and protease inhibitors). OCX21, a protein highly concentrated in the fluid and the shell, belongs to this group. A third group equally represented at all stages of shell mineralization corresponded to antibacterial proteins that could protect the forming egg against microbial invasion.
The calcitic avian eggshell protects the developing embryo and, moreover, ensures that the nutritious table egg remains free of pathogens. The eggshell is formed by nucleation upon a fibrous scaffold (the eggshell membranes) followed by an interaction between the growing mineral crystals and the shell organic matrix. This interaction leads to a highly ordered shell microstructure and texture which contribute to its exceptional mechanical properties. Shell mineralization occurs in three distinct phases of calcification (initiation, growth and termination), which are associated with distinct populations of matrix proteins that are secreted into the acellular uterine fluid as modulators of the process. The recent development of high-throughput methods has led to the identification of many proteins in the shell, but little is known concerning their role in shell formation. In order to determine precisely the importance of particular proteins relative to eggshell mineralization, this project used qualitative and quantitative proteomics of the uterine fluid constituents, coupled with bioinformatic analysis, to predict the functional role of proteins secreted at each of the three main stages of shell calcification. Besides its relevance to food production and to hen reproduction, eggshell calcification is furthermore a relevant model for studying calcium carbonate biomineralization on a two-dimensional membrane support. Better understanding of this process will provide insight into the fabrication of ceramics at ambient pressure and temperature.
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•Avian uterine fluid proteins were quantified at three stages of shell mineralization.•The changes with stages of mineralization revealed 5 protein profile abundances.•Proteins related to mineralization predominate at the onset of shell calcification.•Chaperone and antiproteases modulate proteins that regulate the calcification process.•Numerous antimicrobial proteins are protecting the egg throughout its formation.
This study provides an integrative description of candidate gene expression across tissues involved in calcium (Ca) metabolism during the egg laying cycle, using the well-defined model of Ca supply ...as fine or coarse particles of calcium carbonate (CaCO3). Plasma and tissue samples were collected from hens at the peak of laying at 0 to 1, 9 to 10, and 18 to 19 h postovulation (PO). After mRNA preparation from the parathyroid gland, medullary bone, liver, kidney, duodenum, and jejunum, gene expressions were quantified using RT-qPCR. The highest levels of parathyroid hormone (PTH) mRNA in the parathyroid gland (P < 0.05), and of the active form of vitamin D3 1.25(OH)2D3 in the plasma (P < 0.01) were observed at 18 to 19 h PO. During this active phase of eggshell formation, bone resorption was attested to high levels of plasma inorganic phosphorus (iP) and the receptor activation of nuclear factor-κB expression in the bone (P < 0.001 and P < 0.05, respectively). At this stage, 5 genes of the transcellular and the paracellular Ca absorption pathways in the intestine (P < 0.05) and the Ca channel transient receptor potential cation channel subfamily V member 5 (P < 0.05), involved in its reabsorption in the kidney, were overexpressed. At 0 to 1 h PO during the subsequent daylight period, 2 candidates of the transcellular and the paracellular Ca pathways (P < 0.05) remained at high levels in the intestine, while calbindin D 28K expression was the highest in the kidney (P < 0.05). As PTH mRNA and 1.25(OH)2D3 were low, bone accretion was likely active at this stage. The phosphaturic hormone fibroblast growth factor 23 (FGF23) was overexpressed at 18 to 19 h PO (P < 0.05) in the bone when plasma iP was high, which suggested a role in the subsequent reduction of P reabsorption in the kidney, as attested to the decreased expression of P cotransporters, leading to iP clearance from the plasma at 0 to 1 h PO (P < 0.05). The low levels of 1.25(OH)2D3 at this stage coincided with increased expression of the 24-hydroxylase gene in the kidney (P < 0.05). In hens fed fine particles of CaCO3, higher plasma levels of 1,25(OH)2D3 and higher expression of several genes involved in bone turnover reflected a stronger challenge to Ca homeostasis. Altogether, these data support the hypothesis that FGF23 could drive vitamin D metabolism in the laying hen, as previously documented in other species and explain the tight link between P and Ca metabolisms.
•A candidate gene approach identified several players of calcium (Ca) homeostasis in the laying hen.•Eggshell formation induced genes involved in intestinal Ca absorption, renal reabsorption, and bone resorption.•A bone-derived hormone stood up as a candidate controlling P to Ca balance during the hens' ovulatory cycle.•Gene expression indicated a lower bone turnover in hens fed an adequate Ca source.
The avian eggshell membranes surround the egg white and provide a structural foundation for calcification of the eggshell which is essential for avian reproduction; moreover, it is also a natural ...biomaterial with many potential industrial and biomedical applications. Due to the insoluble and stable nature of the eggshell membrane fibres, their formation and protein constituents remain poorly characterized. The purpose of this study was to identify genes encoding eggshell membrane proteins, particularly those responsible for its structural features, by analyzing the transcriptome of the white isthmus segment of the oviduct, which is the specialized region responsible for the fabrication of the membrane fibres.
The Del-Mar 14 K chicken microarray was used to investigate up-regulated expression of transcripts in the white isthmus (WI) compared with the adjacent magnum (Ma) and uterine (Ut) segments of the hen oviduct. Analysis revealed 135 clones hybridizing to over-expressed transcripts (WI/Ma + WI/Ut), and corresponding to 107 NCBI annotated non-redundant Gallus gallus gene IDs. This combined analysis revealed that the structural proteins highly over-expressed in the white isthmus include collagen X (COL10A1), fibrillin-1 (FBN1) and cysteine rich eggshell membrane protein (CREMP). These results validate previous proteomics studies which have identified collagen X (α-1) and CREMP in soluble eggshell extracts. Genes encoding collagen-processing enzymes such as lysyl oxidase homologs 1, 2 and 3 (LOXL1, LOXL2 and LOXL3), prolyl 4 hydroxylase subunit α-2 and beta polypeptide (P4HA2 and P4HB) as well as peptidyl-prolyl cis-trans isomerase C (PPIC) were also over-expressed. Additionally, genes encoding proteins known to regulate disulfide cross-linking, including sulfhydryl oxidase (QSOX1) and thioredoxin (TXN), were identified which suggests that coordinated up-regulation of genes in the white isthmus is associated with eggshell membrane fibre formation.
The present study has identified genes associated with the processing of collagen, other structural proteins, and disulfide-mediated cross-linking during eggshell membrane formation in the white isthmus. Identification of these genes will provide new insight into eggshell membrane structure and mechanisms of formation that will assist in the development of selection strategies to improve eggshell quality and food safety of the table egg.
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