Eggshell translucency: its relationship with specific gravity and eggshell color and its influence on broiler egg weight loss, hatchability, and embryonic mortalities

Eggshell quality is among the most important factors affecting hatchability in broiler breeders, and therefore several methods for its assessment are available in the poultry industry. Among them, eggshell translucency has received special attention in recent years due to its connection with ultrastructural disorganization of the shell layers. However, there is very limited data on the impact of translucency on hatching eggs and on the possible links between this trait and specific gravity (SG) or shell color. Thus, our study investigated associations and interactions between eggshell translucency, SG, and color on incubation parameters of eggs from the same breeding flock (Ross 308AP, 51 wk of age). To this end, light and dark eggs within 5 different SG categories (≥1.065, 1.070, 1.075, 1.080, and ≤1.085) were selected from 15,976 eggs, graded into 3 translucency scores, and later incubated to evaluate egg weight loss, hatchability and embryonic mortalities. In general, translucency scores were evenly distributed within SG categories (χ2 [8, N = 1,138] = 13.67, P = 0.090) and color (χ2 [2, N = 1,138] = 4.93, P = 0.084). No interactions between eggshell translucency and SG or between translucency and color were found for the analyzed variables. An interaction was observed between SG and eggshell color for the variable egg weight loss, where the light-shelled eggs, in most SG categories lost more weight throughout incubation than dark eggs. Eggshell translucency affected egg weight loss, hatchability, and embryonic mortality on 11 to 18 d of incubation, with highly translucent eggs showing the worst results. At the same time, eggs with SG lower than 1.070 displayed the greatest weight loss, lowest hatchability, and highest contamination. We found no influence of eggshell color on weight loss or hatchability, but light-shelled eggs exhibited higher late embryonic mortality. Together, these data suggest that despite its effects on certain hatching parameters, shell translucency bears no relationship to SG or color.

Differential physiological response of slow- and fast-growing broiler lines to hypoxic conditions during chorioallantoic membrane development

Ambient conditions during chicken embryogenesis, such as insufficient oxygen or changes in temperature, are expected to cause permanent phenotypic changes and affect their posthatch performance. Decades of genetic selection for high growth rate resulted with various physiological and morphological changes that can affect the broiler fitness under environmental stress. To evaluate the selection effect on responses to environmental challenge during embryonic development, and the long-term implications, we have used a unique genetic line, that was not selected for over 30 yr (since 1986), as control for the modern commercial genetic line. At embryonic day 5 (E5), broiler embryos from these 2 genetic lines were divided into 2 treatments: 1) control; 2) 15% O2 concentration for 12 h/day from E5 through E12 the embryonic period of chorioallantoic membrane formation. Embryos and hatched chicks were characterized for physiological and morphological parameters. Significant differences in relative embryo weight and yolk consumption were found between the 2 lines. The modern line was characterized by a higher metabolic rate and rapid growth, supported by higher hemoglobin levels and hematocrit concentrations, whereas the 1986 line had slower metabolism, lower levels of hematocrit and hemoglobin, higher oxygen volume per 1 g of embryonic tissue indicating higher oxygen availability. Both lines exhibited changes in heart rate, and blood parameters corresponding to cardiovascular system adaptation after hypoxic exposure, seemingly implemented to increase oxygen-carrying capacity to the embryo tissues. Our finding stand in agreement that the genetic selection for high growth rate that led to higher metabolism without a fit of the cardiovascular system, increased the imbalance between oxygen supply and demand.

Transcriptomic and Epigenetic Preservation of Genetic Sex Identity in Estrogen-feminized Male Chicken Embryonic Gonads

Whereas in ovo exposure of genetically male (ZZ) chicken embryos to exogenous estrogens temporarily feminizes gonads at the time of hatching, the morphologically ovarian ZZ-gonads (FemZZs for feminized ZZ gonads) are masculinized back to testes within 1 year. To identify the feminization-resistant "memory" of genetic male sex, FemZZs showing varying degrees of feminization were subjected to transcriptomic, DNA methylome, and immunofluorescence analyses. Protein-coding genes were classified based on their relative mRNA expression across normal ZZ-testes, genetically female (ZW) ovaries, and FemZZs. We identified a group of 25 genes that were strongly expressed in both ZZ-testes and FemZZs but dramatically suppressed in ZW-ovaries. Interestingly, 84% (21/25) of these feminization-resistant testicular marker genes, including the DMRT1 master masculinizing gene, were located in chromosome Z. Expression of representative marker genes of germline cells (eg, DAZL or DDX4/VASA) was stronger in FemZZs than normal ZZ-testes or ZW-ovaries. We also identified 231 repetitive sequences (RSs) that were strongly expressed in both ZZ-testes and FemZZs, but these RSs were not enriched in chromosome Z. Although 94% (165/176) of RSs exclusively expressed in ZW-ovaries were located in chromosome W, no feminization-inducible RS was detected in FemZZs. DNA methylome analysis distinguished FemZZs from normal ZZ- and ZW-gonads. Immunofluorescence analysis of FemZZ gonads revealed expression of DMRT1 protein in medullary SOX9+ somatic cells and apparent germline cell populations in both medulla and cortex. Taken together, our study provides evidence that both somatic and germline cell populations in morphologically feminized FemZZs maintain significant transcriptomic and epigenetic memories of genetic sex.

Preliminary evaluation of application of a 3-dimensional network structure of siloxanes Dergall preparation on chick embryo development and microbiological status of eggshells

The spatial network structure of Dergall is based on substances nontoxic to humans and the environment which, when applied on solid surfaces, creates a coating that reduces bacterial cell adhesion. The bacteriostatic properties of siloxanes are based on a purely physical action mechanism which excludes development of drug-resistant microorganisms. The aims of the present study were to 1) evaluate a Dergall layer formed on the eggshell surface regarding the potential harmful effects on the chick embryo; 2) evaluate antimicrobial activity and estimate the prolongation time of Dergall's potential antimicrobial activity. Dergall at a concentration of 0.6% formed a layer on the eggshell surface. In vitro testing of the potential harmful effects of Dergall by means of a hen embryo test of the chorioallantoic membrane showed no irritation reaction at a concentration of 3% and lower. The hatchability of the groups sprayed with a Dergall water solution with a concentration of 0 to 5% was 89.1 to 93.8% for fertilized eggs (P > 0.05) but decreased to 63.7% (P < 0.05) in the group sprayed with a 6% concentration of the solution. This phenomenon was caused by embryo mortality in the first week of incubation. At the concentration of 0.6%, Dergall exhibited strong antibacterial properties against bacteria such as Staphylococcus aureus, Escherichia coli, Shigella dysenteriae, Shigella flexneri, and Salmonella typhimurium. For Streptococcus pyogenes, the highest antibacterial activity of Dergall was reported in the concentrations of 100 and 50%. For Pseudomonas aeruginosa, no antibacterial activity of Dergall was generally observed, but in vivo testing showed a strong decrease of all gram-negative bacteria growth. Moreover, a prolonged antimicrobial effect lasting until 3 D after disinfection was observed, which makes Dergall a safe and efficient disinfectant.

Effects of stage of broiler embryo development on coccidiosis vaccine injection accuracy, and subsequent oocyst localization and hatchling quality

Control of coccidiosis in broiler chickens continues to pose challenges to commercial poultry producers, especially in an era of increased consumer demand for antibiotic-free broiler production. As a result, coccidiosis vaccines are now commonly used in rotation programs to achieve effective coccidiosis control. Inovocox EM1 vaccine (EM1) is a coccidiosis vaccine that allows for earlier immune acquisition through oocyst cycling, which reduces the effects of wild-type coccidia. The EM1 vaccine is administered to embryonated broiler hatching eggs between 18 and 19 D of incubation (doi). In the U.S., commercial broiler hatcheries vaccinate embryonated eggs at either 18.5 or 19 doi. However, it is unclear whether a difference in embryo age at the time of in ovo injection can impact the actual site of vaccine delivery. In addition, it is unclear where oocysts eventually become localized within the embryo following the in ovo injection of EM1. Therefore, the objective of this study was to determine the effects of stage of embryonic development on the actual deposition site of the EM1 vaccine oocysts when they are in ovo injected and to subsequently investigate the movement and eventual location of EM1 oocysts after in ovo injection. Because all eggs were injected at the same time, a 12-h difference in set time was a means to derive 18.5 and 19.0 incubation age of injection (IAN) treatments. The experimental design was a 3 injection treatment (noninjected, diluent-injected, and vaccine-injected) × 2 IAN factorial. There was a significant main effect of IAN on site of vaccine oocysts delivery, and subsequent hatching chick quality. Qualitative histological evaluation revealed the oral uptake of vaccine oocysts through the amnion, with their subsequent presence in the gizzard and intestinal lumen by 24 to 36 h postinjection. In conclusion, physiological development influenced the site of injection, and oocysts imbibed along with the amniotic fluid in late stage broiler embryos are subsequently transported to the gastrointestinal tract.

Maternal conjugated linoleic acid alters hepatic lipid metabolism via the AMPK signaling pathway in chick embryos

The effects of maternal conjugated linoleic acid (CLA) on embryonic development and hepatic lipid metabolism were investigated in chick embryos. A total of 180 Arbor Acres female broiler breeders (36 wk old) were randomly divided into the following 3 dietary treatment groups: a basic diet (control), a basic diet containing 0.5% CLA (CLA1), and a basic diet containing 1.0% CLA (CLA2). The females were fed for 8 wk, and the eggs from each group were collected and hatched during the last 2 wk. The results showed that the addition of dietary CLA increased the broken egg rate and reduced the fertilization rate and the egg hatchability (P < 0.05). CLA enrichment decreased the polyunsaturated and monounsaturated fatty acids and increased the saturated fatty acids in the yolk sac (P < 0.05). The yolk sac weight, body weight, and body length had a linear decrease with CLA supplementation (P < 0.05). In the developing chick embryo (at E14) and newly hatched chick (D0), the serum triglyceride concentration decreased with maternal CLA supplementation and was accompanied by a reduction in subcutaneous adipose tissue deposition. In addition, maternal CLA supplementation mediated the hepatic lipid metabolism by decreasing the mRNA expression of sterol regulatory element-binding proteins-1c (SREBP-1c), fatty acid synthase and acetyl-CoA carboxylase, and increasing the mRNA expression of adenosine 5'-monophosphate-activated protein kinase α (AMPKα), peroxisome proliferator-activated receptors α (PPARα), liver fatty acid-binding protein, adipose triglyceride lipase and carnitine palmitoyltransferase in embryonic chick livers (P < 0.05). A drop in SREBP-1c protein expression and an increase in the protein expression of p-AMPKα and PPARα were also observed in the liver of chick embryo (P < 0.05). In conclusion, maternal CLA supplementation regulated the fatty acid composition in the yolk sac, and mediated embryonic chick development and hepatic lipometabolism, and these effects may be related to the AMPK pathway. These findings suggest the potential ability of maternal CLA supplementation to reduce fat deposition in chick embryos.

Immune responses upon in ovo HVT-IBD vaccination vary between different chicken lines

The genotype of chickens is assumed to be associated with variable immune responses. In this study a modern, moderate performing dual-purpose chicken line (DT) was compared with a high-performing layer-type (LT) as well as a broiler-type (BT) chicken line. One group of each genotype was vaccinated in ovo with a recombinant herpesvirus of turkeys expressing the virus protein VP2 of the infectious bursal disease virus (HVT-IBD) while one group of each genotype was left HVT-IBD unvaccinated (control group). Genotype associated differences in innate and adapted immune responses between the groups were determined over five weeks post hatch. HVT-IBD vaccination significantly enhanced humoral immune responses against subsequently applied live vaccines compared to non-HVT-IBD vaccinated groups at some of the investigated time points (P < 0.05). In addition HVT-IBD vaccination had depending on the genotype a significant impact on splenic macrophage as well as bursal CD4⁺ T-cell numbers (P < 0.05). On the other hand, the detectable genotype influence on Interferon (IFN) γ and nitric oxide (NO) release of ex vivo stimulated spleen cells was independent of HVT-IBD vaccination. The results of our study suggest considering a genotype specific vaccination regime in the field.

Integrated Proteomic and N-Glycoproteomic Analyses of Chicken Egg during Embryonic Development

To better appreciate the alterations of egg proteins and their modifications during embryonic development, a comparative and quantitative study was performed aimed at chicken egg white and yolk proteome and N-glycoproteome after 12 days of incubation using tandem mass tag (TMT)-labeling technology in conjunction with reversed-phase high-performance liquid chromatography (RP-HPLC). A total of 334 unique N-glycosite-containing peptides from 153 N-glycoproteins were identified, of which 82 N-glycosite-containing peptides showed significant changes after 12 days of incubation. The varied proteome was mainly involved with antibacterial, ionic binding, cell proliferation, and embryonic development, while the different degrading and/or absorbing priorities of egg proteins were proposed. This study provides substantial insight into the effects of N-glycoprotein variations on the utilization of egg proteins by chicken embryo during incubation.

Sulforaphane Rescues Ethanol-Suppressed Angiogenesis through Oxidative and Endoplasmic Reticulum Stress in Chick Embryos

Our previous study showed that ethanol exposure inhibited embryonic angiogenesis mainly due to the excessive stimulation of reactive oxygen species (ROS) production. In this study, we investigated whether sulforaphane (SFN), a known dietary bioactive compound, could ameliorate ethanol-suppressed angiogenesis using chick embryo angiogenesis models. Using chick yolk sac membrane (YSM) and chorioallantoic membrane (CAM) models, we demonstrated that administration of low concentrations of SFN (2.5-10 μM) alone increased angiogenesis, but high concentrations of SFN (20-40 μM) inhibited angiogenesis. SFN administration alleviated ethanol-suppressed angiogenesis and angiogenesis-related gene expression in both angiogenesis models. Ethanol exposure caused cell apoptosis in chick CAM, and the cell apoptosis could be remitted by administration of SFN. Subsequently, we demonstrated that the ethanol-induced increase in production of ROS and reduction of antioxidant enzymes' activity were partially rescued by SFN. Similar results were obtained in endoplasmic reticulum (ER) stress determination, indicated by ATF6 and GRP78 expression or thapsigargin-induced ER stress in the presence or absence of SFN. Taken together, our experiments show that SFN administration can ameliorate ethanol-suppressed embryonic angiogenesis, and this is mainly achieved by alleviating excessive ROS production and ER stress. This study suggests that SFN, in appropriate concentrations, could be a potential candidate compound for preventing the negative impact of alcohol on angiogenesis.

Spatial transcriptional profile of PepT1 mRNA in the yolk sac and small intestine in broiler chickens

The yolk sac and small intestine are 2 important organs responsible for the digestion and absorption of nutrients in chickens during the embryonic and posthatch periods, respectively. The peptide transporter PepT1 is expressed in both the yolk sac and small intestine and plays an important role in the transport of amino acids as short peptides. The objective of this study was to profile the spatial transcriptional patterns of PepT1 mRNA in the yolk sac and small intestine from embryonic and posthatch broilers. The distribution of PepT1 mRNA was investigated by in situ hybridization at embryonic (e) d 11, 13, 15, 17, 19 and day of hatch (doh) in the yolk sac and at e19, doh, and d 1, d 4, and d 7 posthatch in the small intestine. PepT1 mRNA was expressed in the endodermal cells of the yolk sac. PepT1 mRNA was barely detectable at e11, increased from e11 to e13, e15, and e17, and then gradually decreased from e19 to doh. In the small intestine, there was a rapid increase in expression of PepT1 mRNA in the enterocytes from e19 to doh, with expression relatively constant from d 1 to d 7. In addition, there was a differential increase in the heights of the villi in different parts of the small intestine from d 1 to 7, which may partially explain the temporal increase in PepT1 mRNA detected by qPCR. The villi in the duodenum showed the earliest increase in villus height and ultimately resulted in the highest villi at d 7. These results demonstrate that there are temporal changes in PepT1 mRNA expression in the yolk sac and the small intestine, which correspond with their expected role in nutrient uptake during the embryonic and posthatch periods.

Effect of administration of glucose on body length and body weight of the chick embryos

OBJECTIVE

To assess the effect of glucose on body length and body weight of chick embryos.

METHODS

This experimental study was carried out at the College of Physicians and Surgeons Pakistan, Islamabad, from January 2013 to January 2014, and comprised chicken eggs. Fertilised eggs of Egyptian Fayyumi breed were injected with glucose (5% weight/volume solution) into egg albumen. The eggs were put in the incubator under standard conditions of temperature and humidity. Eggs were divided in two groups; control group A and experimental group B. Each group was subdivided in three subgroups. Eggs were opened on day 12 (A1, B1), day 15(A2, B2), and day 18(A3, B3) of incubation and the dissected-out embryos were compared with age-matched control subgroups. Effects of glucose were assessed by measuring the body weight and body length of embryos.

RESULTS

Of the 180 eggs, there were 30(16.67%) in each of the 6 subgroups. The mean body length was 6.527±0.086cm in A1 and 5.287±0.035 in B1 (p=0.001); 9.560±0.095 in A2 and 9.237±0.114 in B2 (p=0.033); and 13.919±0.093 in A3 and 16.117±0.103 in B3 (p=0.000). Similarly, the mean body weight was 4.374±0.071 in A1 and 3.676±0.007 in B1 (p=0.001); 10.814±0.214 in A2 and 11.009±0.339 in B2 (p=0.619); and 18.142±0.123 in A3 and 22.87±0.067 in B3 (p=0.000)..

CONCLUSIONS

Administration of glucose resulted in initial growth retardation of developing embryos but later on there was significant growth acceleration as the age advanced.

Effects of Glucose Administration on Development of Sclera in Chick Embryos

OBJECTIVE

To determine the effect of glucose administration on the development of sclera in the chick embryo Gallus domesticus.

STUDY DESIGN

Experimental study.

PLACE AND DURATION OF STUDY

Anatomy Department, CPSPRegional Centre, Islamabad, from January 2013 to January 2014.

METHODOLOGY

The study was carried out in two main groups, control Aand experimental B, which were subdivided into three subgroups comprising 30 eggs each. The group Awas injected with normal saline (0.3 ml) in the egg albumen. The group B was injected with 0.3 ml of 5% w/v solution of glucose equivalent to 15 mg of glucose. Subgroups A1 and B1 were opened on day 10 of incubation. Subgroups A2 and B2 were sacrificed on day 12 of incubation. Eggs from subgroups A3 and B3 were opened on day 15 of incubation. Experimental subgroups were compared with matched control subgroups and quantitative data was analysed statistically.

RESULTS

Administration of glucose resulted in changes in thickness of sclera. The mean thickness (µm) of sclera at day 10 of incubation was 43.54 ±2.45 in control subgroup and 43.03 ±5.86 in the experimental subgroup (p=0.673). The mean thickness (µm) of sclera at day 15 of incubation 77.48 ±8.32 in control subgroup and 73.99 ±8.62 in experimental subgroup (p=0.145). The mean number of chondrocytes/unit area of hyaline cartilage of sclera in day 10 was 17.40 ±1.44 control subgroup and 14.57 ±1.87 in the experimental subgroup (p < 0.001). The mean number of chondrocytes/unit area of hyaline cartilage of sclera on day 15 was 10.02 ±0.86 in the control subgroup and 9.54 ±0.59 in the experimental subgroup (p=0.025). There was disrupted ossicular formation indicating adverse effects on the development of bony sclera as well.

CONCLUSION

Administration of glucose caused alteration in the histology of sclera in developing chick embryos.

Expression of prolyl hydroxylases 2 and 3 in chick embryos

Hypoxic cellular response is crucial for normal development as well as in pathological conditions in order to tolerate low oxygen. The response is mediated by Hypoxia Inducible Factors (HIFs), where the α-subunit of HIF is stabilised and able to function only in low oxygen. Prolyl hydroxylases (PHDs) are oxygen dependent dioxygenase enzymes that hydroxylate HIF-α leading to HIF degradation. Thus PHDs function as an oxygen sensor for the function of HIFs. Here we describe the mRNA expression pattern of PHDs in chick embryos. Up to embryonic day 2, PHDs are weak without specific localisation, whereas from day 3 localised expression was observed in the eye, branchial arches and dermomyotome. Later in the limb development PHDs were expressed in the perichondral mesenchyme, excluded from the developing limb cartilages.

Expression of thyroid hormone transporters and deiodinases at the brain barriers in the embryonic chicken: Insights into the regulation of thyroid hormone availability during neurodevelopment

Thyroid hormones (THs) are key regulators in the development of the vertebrate brain. Therefore, TH access to the developing brain needs to be strictly regulated. The brain barriers separate the central nervous system from the rest of the body and impose specific transport mechanisms on the exchange of molecules between the general circulation and the nervous system. As such they form ideal structures for regulating TH exchange between the blood and the brain. To investigate the mechanism by which the developing brain regulates TH availability, we investigated the ontogenetic expression profiles of TH transporters, deiodinases and the TH distributor protein transthyretin (TTR) at the brain barriers during embryonic and early postnatal development using the chicken as a model. In situ hybridisation revealed expression of the TH transporters monocarboxylate transporter 8 (MCT8) and 10 (MCT10), organic anion transporting polypeptide 1C1 (OATP1C1) and L-type amino acid transporter 1 (LAT1) and the inactivating type 3 deiodinase (D3) in the choroid plexus which forms the blood-cerebrospinal fluid barrier. This was confirmed by quantitative PCR which additionally indicated strongly increasing expression of TTR as well as detectable expression of the activating type 2 deiodinase (D2) and the (in)activating type 1 deiodinase (D1). In the brain capillaries forming the blood-brain barrier in situ hybridisation showed exclusive expression of LAT1 and D2. The combined presence of LAT1 and D2 in brain capillaries suggests that the blood-brain barrier forms the main route for receptor-active T3 uptake into the embryonic chicken brain. Expression of multiple transporters, deiodinases and TTR in the choroid plexus indicates that the blood-cerebrospinal fluid barrier is also important in regulating early TH availability. The impact of these barrier systems can be deduced from the clear difference in T3 and T4 levels as well as the T3/T4 ratio between the developing brain and the general circulation. We conclude that the tight regulation of TH exchange at the brain barriers from early embryonic stages is one of the factors needed to allow the brain to develop within a relative microenvironment.

Sonic hedgehog overexpression regulates the neuroepithelial cells proliferation in the spinal cord of dorsal regions during chicken embryo development

OBJECTIVE

Sonic hedgehog(SHH) is early expressed in the floor plate and notochord during the development of chicken embryo, which is required for the establishment of dorsal axis and the formation of spinal cord, but the mechanism of SHH affecting the patterns of spinal development is still unclear.

METHODS

In this study using in vivo electroporation ectopic expression of SHH in spinal cord of dorsal regions during chicken embryo development. Besides, the expression of NF, TAG, Pax-7 and N-Cadherin was examined by the fluorescent immunohistochemistry.

RESULTS

The result showed that the pattern of spinal cord development changed such as the distortion was observed during the chicken embryo development, and the location of dorsal root transforms from the original site to the roof plate, and neuroepithelial cell layer at the roof plate creased. Furthermore, the expression of nuclear protein Pax-7 was inhibited at the site of SHH ectopic and the expression site of neurofilament(NF) and TAG-1 changed, while the expression of SC-1 was down-regulated.

CONCLUSIONS

This study demonstrated that SHH may be directly required for the formation of spinal patterns or affect the formation of spinal cord through regulating the associated proteins and more important is SHH promote the neuroepithelial cells proliferation and then lead to neural plate to form the neural tube. This study could provide reliable references for the research on SHH determining the formation of spinal cord during the development of chicken embryo.

Identification of novel regulatory genes in development of the avian reproductive tracts

The chicken reproductive system is unique in maintaining its functions including production of eggs or sperm, fertilization of the egg by sperm maintained in sperm nests, production of hormones regulating its growth, development and function, and reproduction. Development of the reproductive organs is a highly regulated process that results in differentiation and proliferation of germ cells in response to predominant regulatory factors such as hormones and transcription factors. However, only a few genes are known to determine morphogenesis of the chicken reproductive tract and their mechanisms are unknown. Therefore, in the present study, we investigated the expression patterns of four genes including SNCA, TOM1L1, TTR and ZEB1 in the gonads at embryonic days 14 and 18, and in immature (12-week-old) and mature (50-week-old) chickens, as well as the reproductive tract including ovary, oviduct and testes of the respective sexes by qRT-PCR, in situ hybridization and immunofluorescence analyses. The expression of SNCA, TOM1L1 and ZEB1 genes was higher in immature and mature female reproductive tracts than expression of TTR. In addition, different temporal and spatial patterns of expression of the four genes were observed during maturation of testis in chickens. Specifically, SNCA, TOM1L1 and TTR were highly expressed in testes of 12-week-old chickens. Moreover, several chicken specific microRNAs (miRs) were demonstrated to affect expression of target gene mRNAs by directly binding to the 3′-UTR of their target genes through actions at the post-transcriptional level as follows: miR-153 and miR-1643 for SNCA; miR-1680* for TTR; and miR-200b and miR-1786 for ZEB1. These results suggest that four-selected genes play an important role in development of the male and female reproductive tract in chickens and expression of most candidate genes is regulated at the post-transcriptional level through specific microRNAs.

Effect of embryonic development on the chicken egg yolk plasma proteome after 12 days of incubation

To better appreciate the dynamics of yolk proteins during embryonic development, we analyzed the protein quantitative changes occurring in the yolk plasma at the day of lay and after 12 days of incubation, by comparing unfertilized and fertilized chicken eggs. Of the 127 identified proteins, 69 showed relative abundance differences among conditions. Alpha-fetoprotein and two uncharacterized proteins (F1NHB8 and F1NMM2) were identified for the first time in the egg. After 12 days of incubation, five proteins (vitronectin, α-fetoprotein, similar to thrombin, apolipoprotein B, and apovitellenin-1) showed a major increase in relative abundance, whereas 15 proteins showed a significant decrease in the yolks of fertilized eggs. In unfertilized/table eggs, we observed an accumulation of proteins likely to originate from other egg compartments during incubation. This study provides basic knowledge on the utilization of egg yolk proteins by the embryo and gives some insight into how storage can affect egg quality.

TOXIC INTERACTION OF CHLORPYRIPHOS AND COPPER SULPHATE ON CHICKEN EMBRYO

The single and simultaneous phytotoxic effect of copper sulphate and Pyrinex 48 EC insecticide were investigated on chicken embryos. The eggs were injected by 0.1 ml of copper sulphate solution (0.05%) and/or by 0.1 ml of Pyrinex 48 EC (chlorpyriphos, 480 g/l; 1%). The treatments were performed on day 0 of incubation, and the embryos were examined on day 3 and 19 of it. Germinal disc was prepared to study the early stage of development. Number of embryonic death, developmental abnormalities and body weight of embryos were recorded on day 19. Liver samples were taken for histology and the skeleton was stained by Dawson method. The embryo mortality was not influenced by single treatment of copper sulphate, however, Pyrinex 48 EC and the combination of the test items significantly increased it on day 3. Same tendency was observed in the case of developmental aberration. Single administration of both test items and their combination significantly increased the embryo mortality on day 19. Frequency of abnormalities was not influenced by copper sulphate but single and simultaneous application of insecticide increased it significantly. Pyrinex 48 EC alone and in combination with copper sulphate significantly reduced the body weight, however, the copper sulphate alone did not influence it. Developmental abnormalities were observed sporadically in all cases. There were no findings of drug-induced hepatopathy, however, the ratio of the mitotic cells were markedly reduced. Based on the results, addition and synergistic toxic interaction may be between the copper sulphate and Pyrinex 48 EC that can highly reduce the viability of the embryos.

Nano-nutrition of chicken embryos. The effect of in ovo administration of diamond nanoparticles and L-glutamine on molecular responses in chicken embryo pectoral muscles

It has been demonstrated that the content of certain amino acids in eggs is not sufficient to fully support embryonic development. One possibility to supply the embryo with extra nutrients and energy is in ovo administration of nutrients. Nanoparticles of diamond are highly biocompatible non-toxic carbonic structures, and we hypothesized that bio-complexes of diamond nanoparticles with l-glutamine may affect molecular responses in breast muscle. The objective of the investigation was to evaluate the effect of diamond nanoparticle (ND) and l-glutamine (Gln) on expression of growth and differentiation factors of chicken embryo pectoral muscles. ND, Gln, and Gln/ND solutions (50 mg/L) were injected into fertilized broiler chicken eggs at the beginning of embryogenesis. Muscle tissue was dissected at day 20 of incubation and analysed for gene expression of FGF2, VEGF-A, and MyoD1. ND and especially Gln/ND up-regulated expression of genes related to muscle cell proliferation (FGF2) and differentiation (MyoD1). Furthermore, the ratio between FGF2 and MyoD1 was highest in the Gln/ND group. At the end of embryogenesis, Gln/ND enhanced both proliferation and differentiation of pectoral muscle cells and differentiation dominated over proliferation. These preliminary results suggest that the bio-complex of glutamine and diamond nanoparticles may accelerate growth and maturation of muscle cells.

Embryological staging of the Zebra Finch, Taeniopygia guttata

Zebra Finches (Taeniopygia guttata) are the most commonly used laboratory songbird species, yet their embryological development has been poorly characterized. Most studies to date apply Hamburger and Hamilton stages derived from chicken development; however, significant differences in development between precocial and altricial species suggest that they may not be directly comparable. We provide the first detailed description of embryological development in the Zebra Finch under standard artificial incubation. These descriptions confirm that some of the features used to classify chicken embryos into stages are not applicable in an altricial bird such as the Zebra Finch. This staging protocol will help to standardize future studies of embryological development in the Zebra Finch.

Toxicity of pendimethalin containing formulation and copper sulphate to chicken embryos

The aim of this study was to determine the individual and combined toxic effects of STOMP 330 EC herbicide (33% pendimethalin) and copper sulphate on the development of chicken embryos. On the first day of incubation chicken eggs were dipped in the solution or emulsion of the test materials for 30 minutes. Applied concentration of copper sulphate was 0.01% and of herbicide STOMP 330 EC was 1.25%. The chicken embryos were examined for the followings: rate of embryo mortality, body weight, type of developmental anomalies, macroscopic examination. Our teratogenicity study revealed that, the individual toxic effect of copper sulphate and pendimethalin containing herbicide formulation (STOMP 330 EC) were embryotoxic but not teratogenic in chicken. The combined administration of STOMP 330 EC and copper sulphate did not increase the embryotoxic effect.

Developmental abnormalities in chicken embryos exposed to N-nitrosoatrazine

Nitrate and atrazine (ATR) occur in combination in some drinking-water supplies and might react to form N-nitrosoatrazine (NNAT), which is reportedly more toxic than nitrate, nitrite, or ATR. Current evidence from population-based studies indicates that exposure to nitrate, nitrite, and nitrosatable compounds increases the risk of congenital defects and/or rate of embryo lethality. To test the hypothesis that NNAT induces malformations during embryogenesis, chicken embryos were examined for lethality and developmental abnormalities after treating fertilized eggs with 0.06-3.63 μg NNAT. After 5 d of incubation (Hamburger and Hamilton stage 27), 90% of embryos in NNAT-treated eggs were alive, of which 23% were malformed. Malformations included heart and neural-tube defects, caudal regression, gastroschisis, microphthalmia, anophthalmia, and craniofacial hypoplasia. The findings from this investigation suggest further studies are needed to determine the mechanisms underlying NNAT-induced embryotoxicity.

Axes, planes and tubes, or the geometry of embryogenesis

The paper presents selected figures of chick embryogenesis as depicted in the classic studies of Caspar Friedrich Wolff (1734-1794), Christian Heinrich Pander (1794-1865) and Karl Ernst von Baer (1792-1786). My main objective here is (1) to demonstrate how the imagery of Wolff, Pander and Baer attempted to project an image of a 3-dimensional rotating body into static figures on paper by means of linear contours, and (2) to ponder on the efficacy and pervasiveness of dots, lines and arrows for depicting embryogenesis.

[Neural crest and vertebrate evolution]

The neural crest (NC) is a remarkable structure of the Vertebrate embryo, which forms from the lateral borders of the neural plate (designated as neural folds) during neural tube closure. As soon as the NC is formed, its constitutive cells detach and migrate away from the neural primordium along definite pathways and at precise periods of time according to a rostro-caudal progression. The NC cells aggregate in definite places in the developing embryo, where they differentiate into a large variety of cell types including the neurons and glial cells of the peripheral nervous system, the pigment cells dispersed throughout the body and endocrine cells such as the adrenal medulla and the calcitonin producing cells. At the cephalic level only, in higher Vertebrates (but along the whole neural axis in Fishes and Amphibians), the NC is also at the origin of mesenchymal cells differentiating into connective tissue chondrogenic and osteogenic cells. Vertebrates belong to the larger group of Cordates which includes also the Protocordates (Cephalocordates and the Urocordates). All Cordates are characterized by the same body plan with a dorsal neural tube and a notochord which, in Vertebrates, exists only at embryonic stages. The main difference between Protocordates and Vertebrates is the very rudimentary development of cephalic structures in the former. As a result, the process of cephalization is one of the most obvious characteristics of Vertebrates. It was accompanied by the apparition of the NC which can therefore be considered as an innovation of Vertebrates during evolution. The application of a cell marking technique which consists in constructing chimeric embryos between two species of birds, the quail and the chicken, has led to show that the vertebrate head is mainly formed by cells originating from the NC, meaning that this structure was an important asset in Vertebrate evolution. Recent studies, described in this article, have strengthened this view by showing that the NC does not only provide the cells that build up the facial skeleton and most of the skull but plays a major role in early brain neurogenesis. It was shown that the cephalic NC cells produce signaling molecules able to regulate the activity of the two secondary organizing centers previously identified in the developing brain: the anterior neural ridge and the midbrain-hindbrain junction, which secrete Fgf8, a potent stimulator of early brain neurogenesis.

Ethanol exposure during the early first trimester equivalent impairs reflexive motor activity and heightens fearfulness in an avian model

Prenatal alcohol exposure is a leading cause of childhood neurodevelopmental disability. The adverse behavioral effects of alcohol exposure during the second and third trimester are well documented; less clear is whether early first trimester-equivalent exposures also alter behavior. We investigated this question using an established chick model of alcohol exposure. In ovo embryos experienced a single, acute ethanol exposure that spanned gastrulation through neuroectoderm induction and early brain patterning (19-22h incubation). At 7 days posthatch, the chicks were evaluated for reflexive motor function (wingflap extension, righting reflex), fearfulness (tonic immobility [TI]), and fear/social reinstatement (open-field behavior). Chicks exposed to a peak ethanol level of 0.23-0.28% were compared against untreated and saline-treated controls. Birds receiving early ethanol exposure had a normal righting reflex and a significantly reduced wingflap extension in response to a sudden descent. The ethanol-treated chicks also displayed heightened fearfulness, reflected in increased frequency of TI, and they required significantly fewer trials for its induction. In an open-field test, ethanol treatment did not affect latency to move, steps taken, vocalizations, defecations, or escape attempts. The current findings demonstrate that early ethanol exposure can increase fearfulness and impair aspects of motor function. Importantly, the observed dysfunctions resulted from an acute ethanol exposure during the period when the major brain components are induced and patterned. The equivalent period in human development is 3-4 weeks postconception. The current findings emphasize that ethanol exposure during the early first trimester equivalent can produce neurodevelopmental disability in the offspring.

Ontogenic expression profiles of thyroid-specific genes in embryonic and hatching chicks

The last trimester of the embryonic life of chickens is marked by a steady increase in circulating thyroxine (T(4)) levels, reaching a maximum around hatching. We have measured thyroidal mRNA expression levels of several genes involved in the biosynthesis of T(4), namely sodium/iodine symporter (NIS), thyroglobulin (Tg), thyroid peroxidase (TPO), thyrotropin receptor (TSHR), and thyroid transcription factor 1 (TTF-1), during this period. Subsequently, we measured the expression of these genes in more detail during the entire hatching process and compared the gene expression profiles with concomitant changes in intrathyroidal and circulating thyroid hormone levels. We found that NIS and TPO mRNA expression increased significantly in the perinatal period, whereas Tg mRNA expression rose gradually throughout the last week of embryogenesis but was stable during hatching. TSHR and TTF-1 mRNA levels did not change significantly during the last week of embryonic development and hatching. Our results suggest that the elevated plasma T(4) levels observed in the developmental period studied are caused by an increased synthesis and secretion of T(4) by the thyroid gland. Augmented expression of Tg may play an important role in the increasing T(4) production during the last week of embryonic development, whereas increased NIS and TPO expression around hatching allows the thyrocytes to boost T(4) synthesis even further.

Identification of critical periods for turning broiler hatching eggs during incubation

(1) Fertile hatchability was superior from a broiler breeder flock at 29 weeks of age than at 68 weeks of age because of decreased mortality at all stages of embryo development. (2) Eggs that were either turned or not turned during the 0 to 7 d, 8 to 14 d and 15 to 18 d periods in the 8 possible combinations showed that the absence of turning from 0 to 7 d of incubation caused a decrease in fertile hatchability and an increase in all stages of embryonic mortality, and an incidence of Malposition II (head in small end of shell) that was more pronounced in a 68-week-old flock than a 29-week-old flock. (3) When eggs from 33- and 35-week-old broiler breeder flocks were either turned or not turned from 0 to 2 d, 3 to 4 d, 5 to 6 d or 7 to 8 d in the 16 possible combinations, the absence of turning from 3 to 8 d, or 0 to 2 d alone or in combination with other time periods reduced fertile hatchability and increased embryonic mortality and percentage of Malposition II. (4) The most critical period for turning commercial broiler hatching eggs during incubation was from 0 to 7 d with the single most critical 2-d period being 0 to 2 d.

Effect of intensity of eggshell pigment and illuminated incubation on hatchability of brown eggs

The effects of intensity of brown eggshell pigment (light (LBP), medium (MBP) and dark (DBP)) and light intensity during incubation (low and high, 900 to 1380 and 1430 to 2080 lux, respectively) on eggshell characteristics, embryonic growth, hatchability traits, chick hatching weight and hatching time were investigated using eggs from a meat-type breeder (Hybro) flock at 32, 36 and 41 weeks of age in three trials. With eggs of similar weights the intensity of brown pigment was not associated with eggshell weight and thickness, and did not influence embryo weight and egg weight loss during incubation. The shade of brown pigment of eggs laid by young hens influenced the percentage hatchability (HP) of eggs incubated under light. Illuminated incubation improved HP of LBP eggs (compared with MBP and DBP eggs) from 32- and 36-week-old hens, but had no significant effect on HP of eggs from 41-week-old hens. Light intensity during incubation did not influence egg weight loss. High intensity of light during incubation reduced HP and increased early death percentage (EDP) in the LBP and MBP groups, and did not influence HP and EDP in the DBP group. Brown eggshell pigment and intensity of light during incubation did not influence hatching time. It is concluded that the shade of brown pigment, intensity of light during incubation and age of the breeder hens influenced the hatchability performance of embryos from brown eggs. Light during incubation improved the hatchability of embryos in light brown eggs laid by young hens and the shade of brown pigment of eggs laid by older hens did not influence hatchability under illuminated incubation. High intensity of light during incubation reduced hatchability of light and medium brown eggs, but not the dark brown eggs.

The ATP-sensitive K(+)-channel (K(ATP)) controls early left-right patterning in Xenopus and chick embryos

Consistent left-right asymmetry requires specific ion currents. We characterize a novel laterality determinant in Xenopus laevis: the ATP-sensitive K(+)-channel (K(ATP)). Expression of specific dominant-negative mutants of the Xenopus Kir6.1 pore subunit of the K(ATP) channel induced randomization of asymmetric organ positioning. Spatio-temporally controlled loss-of-function experiments revealed that the K(ATP) channel functions asymmetrically in LR patterning during very early cleavage stages, and also symmetrically during the early blastula stages, a period when heretofore largely unknown events transmit LR patterning cues. Blocking K(ATP) channel activity randomizes the expression of the left-sided transcription of Nodal. Immunofluorescence analysis revealed that XKir6.1 is localized to basal membranes on the blastocoel roof and cell-cell junctions. A tight junction integrity assay showed that K(ATP) channels are required for proper tight junction function in early Xenopus embryos. We also present evidence that this function may be conserved to the chick, as inhibition of K(ATP) in the primitive streak of chick embryos randomizes the expression of the left-sided gene Sonic hedgehog. We propose a model by which K(ATP) channels control LR patterning via regulation of tight junctions.

Spots and stripes: pleomorphic patterning of stem cells via p-ERK-dependent cell chemotaxis shown by feather morphogenesis and mathematical simulation

A key issue in stem cell biology is the differentiation of homogeneous stem cells towards different fates which are also organized into desired configurations. Little is known about the mechanisms underlying the process of periodic patterning. Feather explants offer a fundamental and testable model in which multi-potential cells are organized into hexagonally arranged primordia and the spacing between primordia. Previous work explored roles of a Turing reaction-diffusion mechanism in establishing chemical patterns. Here we show that a continuum of feather patterns, ranging from stripes to spots, can be obtained when the level of p-ERK activity is adjusted with chemical inhibitors. The patterns are dose-dependent, tissue stage-dependent, and irreversible. Analyses show that ERK activity-dependent mesenchymal cell chemotaxis is essential for converting micro-signaling centers into stable feather primordia. A mathematical model based on short-range activation, long-range inhibition, and cell chemotaxis is developed and shown to simulate observed experimental results. This generic cell behavior model can be applied to model stem cell patterning behavior at large.

Dose related shifts in the developmental progress of chick embryos exposed to mobile phone induced electromagnetic fields

BACKGROUND

The possible adverse effects of Electromagnetic Fields (EMFs) emitted from mobile phones present a major public concern today. Some studies indicate EMFs effects on genes, free radical production, immunological and carcinogenic effects. On the other hand there are studies which do not support the hypothesis of any biological impacts of EMFs. This study was designed to observe the effects of mobile phone induced EMFs on survival and general growth and development of chick embryo, investigating dose-response relationship if any.

METHODS

This was an experimental study in which developing chick embryos were exposed to different doses of mobile phone induced EMFs. For this purpose a mobile phone was placed in the incubator in the centre of fertilised eggs in silent ringing mode and was 'rung' upon from any other line or cell phone. After incubation for 10 or 15 days the eggs were opened and the developmental mile-stones of the surviving embryos were compared with the non exposed subgroup.

RESULTS

EMFs exposure significantly decreased the survivability of the chick embryos. The lower doses of EMFs caused growth retardation. However, this effect of growth retardation reallocated to partial growth enhancement on increasing the dose of EMFs and shifted over to definite growth enhancement on further raising the dose.

CONCLUSION

There is an adverse effect of EMFs exposure on embryo survivability. Chick embryos developmental process is influenced by EMFs. However, these effects are variable depending upon the dose of EMFs exposure.

Expression of Newcastle disease virus (NDV) M protein from a recombinant plasmid prolongs the survival of NDV-infected chicken embryos and enhances the virus replication

To explore the role of M protein in the replication of NDV in chicken embryos, the M gene was cloned and inserted into plasmid pcDNA4.0. Western blot analysis showed that the M protein was expressed in DF-1 cells after transfection with M gene plasmid. Chicken embryonated eggs inoculated with the M gene plasmid and 2 days later infected with NDV showed 10 times higher hemagglutination (HA) titers and an increased survival of the embryos as compared with the embryos inoculated with the empty plasmid. These data indicated that the expression of M protein in the NDV-infected chicken embryos primarily prolonged their survival and consequently enhanced virus replication.

Identification and characterization of the precursor of chicken matrix metalloprotease 2 (pro-MMP-2) in hen egg

Using zymography and mass spectrometry, we identified for the first time the precursor of chicken matrix metalloprotease 2 (pro-MMP-2) as a complex with TIMP-2 (tissue inhibitor of metalloproteinases) in egg white and yolk. Real-time polymerase chain reaction confirmed that MMP-2 and its inhibitors TIMP-2 and TIMP-3 were expressed all along the oviduct and in the liver of laying hens. We also demonstrated that the processing of pro-MMP-2 into mature MMP-2 by serine proteases does not occur in vivo, although purified pro-MMP-2 undergoes proteolytic maturation by these proteases in vitro. Moreover, the relative pro-MMP-2 activity assessed by gelatin zymography was shown to decrease in egg white during the storage of unfertilized or fertilized eggs. However, the mature form of 62 kDa MMP-2 could not be detected. The fact that MMP-2 is found as a proform in fresh eggs suggests that the activity of this metalloprotease is regulated under specific conditions during embryonic development.

Inter‐relationship between egg weight, parental age and embryonic development

A clear positive correlation was evident between egg weight at setting and embryo weight at 18 d of incubation for eggs laid at or after 32 weeks of age. The weight of embryos from the same size eggs were found to depend upon a curvilinear function of the age of parent flock, with the largest increase in embryo weight occurring between 28 and 32 weeks of age. Hatching weight was highly correlated with egg size at setting. Flock age had no effect on hatching weight from a particular sized egg. Within any of the five ages studied, chicks from smaller eggs tended to hatch slightly (but not significantly) earlier than those from larger eggs.

[3D-X-ray microcomputer tomography and optical coherence tomography as methods for the localization of the blastoderm in the newly laid unincubated chicken egg]

The routine culling of the male offspring of hybrid layer type chickens is met with increasing public disapproval for both ethical and legal reasons. Until now practice-oriented methods for reliable sex diagnosis prior to hatch could not be developed. Molecular genetical analysis of blastodermic cells can be used for sex determination in unincubated eggs; however, knowledge of the precise localization of the germinal disc is crucial for the extraction of a carefully directed cell biopsy. In principle, 3D-X-ray micro computed tomography (3D-CT) has been proven a suitable method to localize the germinal disk in the unincubated egg without damaging the egg shell. No negative effects on embryogenesis and hatching rate of irradiated hatching eggs were established. The pictorial representation of the germinal disk using optical coherence tomography (OCT) failed in the unopened egg. The egg shell formed an impenetrable barrier for the currently available measuring method which utilized near infrared (NIR) wavelength regions. After opening the egg shell, the germinal disk could be visualized without any difficulties. In conclusion, technical possibilities for localization of the germinal disk in the unincubated egg already exist, but regarding technical parameters, the procedures have to be adapted to the specific purpose.

Effects of eggshell temperature and oxygen concentration on embryo growth and metabolism during incubation

Embryo development and heat production (HP) were studied in eggs of similar size (60 to 65 g) that were incubated at normal (37.8 degrees C) or high (38.9 degrees C) eggshell temperature (EST) and exposed to low (17%), normal (21%), or high (25%) O(2) concentration from d 9 through 19. High EST initially increased HP, but gradually O(2) became more important for HP than EST. Finally,HP was highest for the combination of high EST with high O(2) and lowest for the combination of high EST with low O(2). High EST decreased hatch time, BW, yolk free BW, and relative heart weight. The EST had no effect on residual yolk weight, chick length, or relative liver weight. Increased O(2) increased yolk free BW and chick length and decreased residual yolk weight at hatch. No interactions between EST and O(2) were observed with regard to embryo development and hatchling characteristics. If embryo development is reflected by HP, it can be concluded that high EST primarily increased embryonic development until the second week of incubation. During the third week of incubation, O(2) had a greater effect in determining embryo development than EST.

[Effects of morphine on the development of chick embryos]

AIM

To investigate the effect of morphine on fetal movement, heart rate, hatch weight, hatch days and hatch rate.

METHODS

Morphine was injected into airspace of eggs and fetal movement, heart rate, hatch weight, hatch days and hatch rates were recorded.

RESULTS

Hatch days were shorter, hatch rates were lower and some chicks became motor disorder for morphine. Chicks with morphine exposure 20 mg/kg from E 12 to E 16 had highest hatch rate and lowest disable rate. Morphine reduced fetal movement, increased heart rate (P < 0.05).

CONCLUSION

The development of chick embryo is impaired by morphine exposure and the magnitude of these effects depends on the drug dose and the length of time that the developing organism is exposed to morphine.

Chickens get their place in the sun

A report on the International Chick Meeting 'The Chick as a Model Organism: Genes, Development and Function', Barcelona, Spain, 11-14 April 2007.

A report on the International Chick Meeting 'The Chick as a Model Organism: Genes, Development and Function', Barcelona, Spain, 11-14 April 2007.

Non-ventilation during early incubation in combination with dexamethasone administration during late incubation: 1. Effects on physiological hormone levels, incubation duration and hatching events

This study investigated the effect of non-ventilation of the incubator during the first 10 days of incubation and its combination with dexamethasone administration at day 16 or 18 of incubation on hatching parameters and embryo and post-hatch chick juvenile physiology. A total of 2400 hatching eggs produced by Cobb broiler breeders were used for the study. Blood samples were collected at day 18 of incubation, at internal pipping stage (IP), at the end of hatch (day-old chick) and at 7-day-post-hatch for T(3), T(4) and corticosterone levels determination. From 448 to 506 h of incubation, the eggs were checked individually in the hatcher every 2h for pipping and hatching. The results indicate that non-ventilation during the first 10-day shortened incubation duration up to IP, external pipping (EP) and hatch, had no effect on hatchability and led to higher T(3) levels at IP but lower corticosterone levels at 7-day-post-hatch. The injection of dexamethasone at days 16 and 18 of incubation affected hatching and blood parameters in both the ventilated and non-ventilated embryos differentially and the effect was dependent on the age of the embryo. Dexamethasone increased T(3) levels and T(3)/T(4) ratios but the effect was greater with early non-ventilation of eggs. Dexamethasone decreased hatchability but the effect was greater when injected at day 16 and especially in ventilated embryos. The effects of incubation protocols and dexamethasone treatments during incubation were still apparent in the hatched chicks until 7 days of age. The changes in T(3), T(4) and corticosterone levels observed in response to the early incubation conditions and late dexamethasone treatments in this study suggest that incubator ventilation or non-ventilation may influence the hypothalamic-pituitary-adrenal axis (HPA) regulation of stress levels (in terms of plasma corticosterone levels) and thyroid function in the embryo with impact on incubation duration, hatching events and early post-hatch life of the chick. Our results also suggest that some stages of development are more sensitive to dexamethasone administration as effects can be influenced by early incubation protocols.

Effect of Four Percent Carbon Dioxide During the Second Half of Incubation on Embryonic Development, Hatching Parameters, and Posthatch Growth

In this study, broiler embryos were exposed during the second half of incubation [embryonic day (ED) 10 until ED18] to 4% CO(2). The CO(2) was set to reach 2% on ED11 and 4% from ED12 onward. Two experiments were conducted with the same setup. Embryo weight was measured and partial pressure of CO(2) and O(2) in the air cell was analyzed at several embryonic ages. Times of internal pipping, external pipping, and hatching were recorded. Chicks were raised until d 7 posthatch. Plasma corticosterone, triiodothyronine, and thyroxine concentrations were determined. Embryonic growth was not retarded and hatchability did not decrease in the CO(2)-incubated group, demonstrating that chicken embryos can tolerate high (4%) concentrations of CO(2) between ED10 and ED18. In the first experiment, partial pressure of CO(2) in the air cell was significantly higher in the CO(2) group on ED11, ED12, ED13, and ED14, but disappeared thereafter. This difference was not observed in the second experiment. A change in the hatching process of the CO(2) group was seen. Relative growths of newly hatched chicks until d 7 posthatch were equal in the CO(2) group and the control group. However, corticosterone and thyroxine concentrations were significantly higher in the CO(2)-incubated chicks on d 7 posthatch.

Muscle development in the embryo and hatchling

Muscle cell proliferation, migration, adhesion, and fusion are processes involved with the formation of multinucleated myotubes that will further differentiate into mature muscle fibers. The process of muscle fiber development is nearly complete at the time of hatch. Muscle growth during the embryonic period of development is characterized by an increase in myoblast cell number through hyperplasia. Posthatch muscle fiber growth occurs through muscle fiber enlargement by the process of hypertrophy, which results from the recruitment of satellite cell nuclei. Hyperplasia and hypertrophy are regulated by factors extrinsic to the cell. These extrinsic elements include growth factors and the extracellular matrix. The growth factors, hepatocyte growth factor, fibroblast growth factor 2, transforming growth factor-beta, insulin-like growth factor, and myostatin stimulate or inhibit myoblast and satellite cell proliferation and differentiation. Some of these growth factors like fibroblast growth factor 2 must interact with a low affinity extracellular matrix macromolecule to bind to their high affinity receptor necessary for cell signaling. It is probable that the expression of extracellular matrix proteins involved in growth factor signaling will affect muscle growth properties during hyperplasia and hypertrophy. As signaling pathways associated with muscle growth mechanisms are further understood, the poultry industry may find it beneficial to include the expression of key genes in their selection strategies.

Development of the chick pancreas with regard to estimation of the relative occurrence and growth of endocrine tissue

Endocrine cells in chick pancreas were observed to map their distribution during development and to perform morphometric studies starting on embryonic day 5. The ratio of exocrine to endocrine tissues first prevailed in favour of the endocrine ones, and changed abruptly after day 9 when rapid growth of exocrine tissue began. Endocrine tissue was formed of two types of islets. The 'light' (or B) islets were composed of insulin-immunoreactive cells, completed perhaps by a few somatostatin-immunoreactive cells occurring on the periphery. The majority of the somatostatin- and glucagon-immunoreactive cells were present in the 'dark' (or A) islets. Endocrine elements were also scattered as single cells over the pancreas. Sporadically, the endocrine cells established contacts with exocrine ducts. In morphometric analysis, volume density of insulin-, glucagon-, and somatostatin-immunoreactive cells was measured, and ratios were calculated between particular components. The volume density of endocrine cells and their ratio appeared stable in individual lobes but varied significantly between each other. Increase of the glucagon volume density is exponential, whereas insulin increases almost linearly especially in splenic lobe. The process results in the increase of the hormone-immunoreactive cell volume density in favour of glucagon-immunoreactive cells typical for birds.

The safety and immunogenicity of an in ovo vaccine against Newcastle disease virus differ between two lines of chicken

Newcastle disease virus is a major threat to poultry and in ovo vaccines are needed. A live in ovo vaccine for Newcastle disease virus, which was licensed but not marketed, was unsafe. It killed 32% of line 0 chicks and 10% of vaccine Lohmann (VALO) chicks using the maximum recommended dose that infected about 40% of the embryos. VALO's made more antibody than line 0's whether infected in ovo or by contact. The vaccine interrupted the massive development of the air capillaries between injection and hatch 3 days later. Cytokines, delivered as DNA in plasmids, did not function as adjuvants. IFN-gamma prevented infection. IL-4 or IL-18 had little or no effect. Line 0 chicks that had been infected by contact were protected and so the unsafe in ovo vaccination of a minority could protect the majority.

High frequency ultrasound imaging of the growth and development of the normal chick embryo

The purpose of this study is to delineate with high frequency ultrasound imaging the normal growth and development of the chick embryo throughout its incubation period. White Leghorn chick embryos were imaged through an opening in the egg air cell from incubation day 0-19 (Hamburger & Hamilton stage 1-45) using a 13 MHz clinical high frequency linear small parts transducer. Multiple anatomic growth parameters were measured. Normal growth was confirmed with Hamburger and Hamilton staging. A timeline was constructed showing when each anatomic growth parameter could be visualized. Means and standard deviations of each parameter were plotted against incubation days studied to create nomograms and numerical tables of normal growth and development of the chick embryo. With this set of data, abnormal growth and development of the chick embryo can now be assessed.

Effects of electrical field on hatchability performance of eggs from a layer-type breeder

1. Eggs from a layer-type breeder flock (Baladi, King Saud University) between 50 and 63 weeks of age were used in three trials to study the effects of electrical field (EF) during incubation on albumen and yolk heights, incubation temperature, egg weight loss and hatchability traits. The effects of egg size and eggshell characteristics on hatchability traits of eggs incubated under EF were investigated. 2. Eggs were weighed and graded into three weight classes (small, medium, and large). The physical dimensions, eggshell characteristics, and conductance of eggs were examined. The incubator was divided into two compartments for the control and EF treatments. Two aluminium plates were fitted on the inside walls of the EF compartment, face to face, and connected to a step up electric transformer. Eggs were exposed constantly to the EF during the first 18 d of incubation at the level of 30 kV/m, 60 Hz. 3. Egg size influenced the physical dimensions and eggshell characteristics of eggs. Large eggs had higher egg weight, egg surface area, egg volume, eggshell conductance, and eggshell weight and lower yolk weight percentage than medium or small size eggs. Small eggs had lower egg length and higher egg density than large or medium size eggs. Large eggs had higher eggshell thickness than small size eggs. 4. EF incubation of eggs raised incubation temperature by 0.06 degrees C, and increased the percentage of egg weight loss, hatchability, and weight of hatching chicks and reduced the early embryo deaths, and length of incubation by approximately 9.8, 19.6, 1.7, 62.1 and 2.1%, respectively. 5. There was no significant difference between the two incubation treatments in the heights of albumen and yolk of incubated eggs, percentages of late embryo deaths, and pips with live and dead embryos. Hatchability traits were not significantly influenced by egg size. 6. It was concluded that EF incubation of eggs increased hatchability, chick-hatching weight, and reduced the length of incubation of Baladi eggs. Differences in the physical dimensions and eggshell characteristics of eggs did not influence hatchability traits of eggs under EF incubation.

Developmentally Regulated Demethylase Activity Targeting the βA-Globin Gene in Primary Avian Erythroid Cells

Differential expression of globin genes has provided an interesting model system for better understanding commonly inherited diseases such as thalassemia. In the avian beta-type globin cluster (5'-rho-betaH-betaA-epsilon-3'), silencing of the embryonic rho-globin gene occurs concomitantly with the activation of the adult betaA-globin gene during embryonic development. DNA methylation is a dynamic process that regulates gene expression. We observed a progressive loss of methylation of betaA-globin gene, during avian embryonic development that was concurrent with the expression of the gene. The promoter and exon 1 regions of the template strand were completely demethylated, whereas residual methylation was retained in exons 2 and 3. Using a modified methylation-sensitive single-nucleotide primer extension (MS-SNuPE) assay, we observed stage-specific demethylase activity in the nuclear extracts of chicken red cells; activity in 5-, 8-, and 11-day-old erythroid cell nuclear extracts was 6, 76, and 24%, respectively. The demethylase targeted both hemimethylated and fully methylated substrates. Our findings demonstrate stage-specific demethylase activity in nuclear extracts from primary chicken erythroid cells that could target the fully methylated promoter of a developmentally regulated native gene.

Spatial and Temporal Expression of Perlecan in the Early Chick Embryo

Perlecan is a major heparan sulfate proteoglycan that binds growth factors and interacts with various extracellular matrix proteins and cell surface molecules. The expression and spatiotemporal distribution of perlecan was studied by RT-PCR, immunoprecipitation and immunofluorescence in the chick embryo from stages X (morula) to HH17 (29 somites). Combined RT-PCR and immunohistochemistry demonstrated the expression of perlecan as early as stage X and its presence may be fundamental to the first basement membrane assembly on the epiblast ventral surface at stage XIII (blastula). Perlecan fluorescence was intense in the cells ingressing through the primitive streak and was strong lining the epiblast ventral surface lateral to the streak at stage HH3-4 (gastrula). At stage HH5-6 (neurula), perlecan fluorescence was low in the neuroepithelium and stronger in the apical surface of the neural plate. At stage HH10-11 (12 somites), perlecan fluorescence was intense in the neuroepithelium and was then essentially nondetectable in the neuroepithelium, and the intensity had shifted to the basement membranes of encephalic vesicles by stage HH17. Perlecan immunofluorescence was intense in neural crest cells, strong in pharyngeal arches, intense in thymus and lung rudiments, intense in aortic arches and in dorsal aorta, strong in lens and retina and intense in intraretinal space and in optic stalk, strong in the dorsal mesocardium, myocardium and endocardium, strong in dermomyotome, low in sclerotome in somites, intense in mesonephric duct and tubule rudiments, intense in the lining of the gut luminal surface. Inhibition of the function of perlecan by blocking antibodies showed that perlecan is crucial for maintaining basement membrane integrity which mediates the epithelialization, adhesive separation and maintenance of neuroepithelium in brain, somite epithelialization, and tissue architecture during morphogenesis of the heart tube, dorsal aorta and gut. An intriguing possibility is that perlecan, as a signaling molecule that modulates the activity of growth factors and cytokines, participates in the signaling pathways that guide gastrulation movements and neural crest cell migration, proliferation and survival, cardiac cell proliferation and paraxial mesoderm (somitic) cell proliferation and segmentation.

Metabolic response to cooling temperatures in chicken embryos and hatchlings after cold incubation

We asked to what extent cold exposure during embryonic growth, and the accompanying hypometabolism, may interfere with the normal development of thermogenesis. White Leghorn chicken eggs were incubated in control conditions (38 degrees C) or at 36 or 35 degrees C. Embryos incubated at a lower temperature (34 degrees C) failed to hatch. The cold-incubated embryos had lower oxygen consumption (VO2) and body weight (W) throughout incubation, and hatching was delayed by about, respectively, 1 and 2 days. The W-VO2 relationship of the cold-incubated embryos was as in controls, indicating that cold-induced hypometabolism was at the expense of the growth, not the maintenance, component of VO2. At embryonic day E11, the metabolic response to changes in ambient temperature (T) over the 30-39 degrees C range was typically poikilothermic, with Q10 = 1.8-1.9, and similar among all sets of embryos. Toward the end of incubation (E20), the thermogenic responses of the cold-incubated embryos were significantly lower than in controls. This difference occurred also in the few-hour old hatchlings (H1), even though, at this time, W was similar among groups. Exposure to cold during only the last 3 days of incubation (from E18 to H1), i.e. during the developmental onset of the endothermic mechanisms, did not lower the thermogenic capacity of the hatchlings. In conclusion, sustained cold-induced hypometabolism throughout incubation blunted the rate of embryonic growth and the development of thermogenesis. This latter phenomenon could be an example of epigenetic regulation, i.e. of environmental factors exerting a long-term effect on gene expression.

Ephrin A/EphA controls the rostral turning polarity of a lateral commissural tract in chick hindbrain

Most post-crossing commissural axons turn into longitudinal paths to make synaptic connections with their targets. Mechanisms that control their rostrocaudal turning polarity are still poorly understood. We used the hindbrain as a model system to investigate the rostral turning of a laterally located commissural tract, identified as the caudal group of contralateral cerebellar-projecting second-order vestibular neurons (cC-VC). We found that the caudal hindbrain possessed a graded non-permissive/repulsive activity for growing cC-VC axons. This non-permissiveness/repulsion was in part mediated by glycosyl-phosphatidylinositol (GPI)-anchored ephrin A. We further demonstrated that ephrin A2 was distributed in a caudal-high/rostral-low gradient in the caudolateral hindbrain and cC-VC axons expressed EphA receptors. Finally,perturbing ephrin A/EphA signalling both in vitro and in vivo led to rostrocaudal pathfinding errors of post-crossing cC-VC axons. These results suggest that ephrin A/EphA interactions play a key role in regulating the polarity of post-crossing cC-VC axons as they turn into the longitudinal axis.

Functional morphology of chorioallantoic vascular network in chicken

The formation, development, and reduction of the capillary network in the chicken chorioallantoic membrane on days 7-20 of egg incubation were studied by light and electron microscopy with morphometry. Specific features in the architectonics and structure of the mesodermal large vessels and their connection to the suprachoroidal capillaries for provision of adequate gas exchange are shown.