Regulatory capacities of a broiler and layer strain exposed to high CO2 levels during the second half of incubation

It has been shown that during embryonic chicken (Gallus gallus) development, the metabolism of broiler embryos differs from that of layers in terms of embryonic growth, pCO2/pO2 blood levels, heat production, and heart rate. Therefore, these strains might adapt differently on extreme environmental factors such as exposure to high CO2. The aim of this study was to compare broiler and layer embryos in their adaptation to 4% CO2 from embryonic days (ED) 12 to 18. Due to hypercapnia, blood pCO2 increased in both strains. Blood bicarbonate concentration was ~10 mmol/L higher in embryos exposed to high CO2 of both strains, while the bicarbonates of broilers had ~5 mmol/L higher values than layer embryos. In addition, the pH increased when embryos of both strains were exposed to CO2. Moreover, under CO2 conditions, the blood potassium concentration increased in both strains significantly, reaching a plateau at ED14. At ED12, the layer strain had a higher increase in CAII protein in red blood cells due to incubation under high CO2 compared to the broiler strain, whereas at ED14, the broiler strain had the highest increase. In conclusion, the most striking observation was the similar mechanism of broiler and layer embryos to cope with high CO2 levels.     

10日龄肉鸡和蛋鸡血清甲状腺激素和胰岛素水平的比较

本实验应用放射免疫分析法,对孵化后１０日龄的肉鸡和蛋鸡血清中三碘甲腺原氨酸（Ｔ３）和甲状腺素（Ｔ４）及胰岛素（Ｉｎｓｕｌｉｎ）水平进行测定。结果如下：在不同品种间,肉鸡的Ｔ３血清浓度显著高于蛋鸡（Ｐ＜０．０１）。尤以雄性间差异更为显著（Ｐ＜０．００１）;Ｉｎｓｕｌｉｎ水平也出现品种间差异,雄性肉鸡显著高于雄性蛋鸡（Ｐ＜０．０１）。在不同性别间,雌性蛋鸡的Ｔ３和Ｉｎｓｕｌｉｎ水平显著高于雄性蛋鸡（Ｐ＜０．０５）,而肉鸡两性别间无明显差异。Ｔ４水平在两品种与两性别间均无明显差异。另外,Ｔ３和Ｉｎｓｕｌｉｎ水平与蛋鸡及雄性肉鸡的个体增重间均呈现明显相关关系（Ｐ＜０．０５）。提示：血中Ｔ３,Ｉｎｓｕｌｉｎ水平均可影响两品种鸡早期不同的生长速率     

An in vitro reconstitution system for the assessment of chromatin protein fluidity during Xenopus development

Chromatin fluidity, which is one of the indicators of higher-order structures in chromatin, is associated with cell differentiation. However, little is known about the relationships between chromatin fluidity and cell differentiation status in embryonic development. We established an in vitro reconstitution system that uses isolated nuclei and cytoplasmic extracts of Xenopus embryos and a fluorescence recovery after photobleaching assay to measure the fluidities of heterochromatin protein 1 (HP1) and histone H1 during development. The HP1 and H1 fluidities of nuclei isolated from the tailbuds of early tadpole stage (stage 32) embryos in the cytoplasmic extracts of eggs and of late blastula stage (stage 9) embryos were higher than those in the cytoplasmic extracts of mid-neurula stage (stage 15) embryos. The HP1 fluidities of nuclei isolated from animal cap cells of early gastrula stage (stage 10) embryos and from the neural plates of neural stage (stage 20) embryos were higher than those isolated from the tailbuds of stage 32 embryos in egg extracts, whereas the HP1 fluidities of these nuclei were the same in the cytoplasmic extracts of stage 15 embryos. These results suggest that chromatin fluidity is dependent upon both cytoplasmic and nuclear factors and decreases during development.     

Effect of nanoparticles of silver and gold on metabolic rate and development of broiler and layer embryos

This investigation evaluated the effects of nanoparticles of silver (AgNano) and gold (AuNano) on metabolic rate (O₂ consumption, CO₂ production and heat production-HP) and the development of embryos from different breeds of broiler and layer chicken. Gaseous exchange was measured in an open-air-circuit respiration unit, and HP was calculated for 10, 13, 16 and 19-day-old embryos. Relative chick and muscle weights were used as a measure of growth rate and development. AgNano but not AuNano increased the rates of O₂ consumption and HP of the layer embryos. The metabolic rate of broiler embryos was not affected by either of the treatments, but it was significantly higher compared to the layer embryos. Neither of the nanoparticles promoted nor depressed growth and development of the embryos, irrespective of breed. Although the metabolic rate of AgNano-injected layer embryos was significantly increased, their BW and muscle weights at hatching were similar to those of the control group, which suggests that the concentration of AgNano used was adequate for increasing the metabolic rate but not enough to affect growth and development. The results show that AgNano could be a potential metabolic modifier for layer embryos; however, the exact mechanism of action should be elucidated in future research.     

Influence of in ovo thermal manipulation on lipid metabolism in embryonic duck liver

The growth and development of poultry embryos are easily affected by environmental factors, such as the incubation temperature and humidity. Metabolism, including lipid metabolism, during the embryonic stage is also important for the growth and development of poultry. Our study aimed to investigate the effects of incubation temperature on embryonic lipid metabolism in the liver of ducks. To fully evaluate the effects, thermal treatment was given between embryonic ages 11 and 24 days with a 1 °C higher incubation temperature than the control group, and lipid metabolism parameters in the liver and blood serum were analyzed both at embryonic stage day 20 and 2 weeks post-hatching. Our results showed no significant changes in the embryonic stage in total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) in the blood serum (P>0.05). Additionally, the mRNA expression levels and enzyme activities of fatty acid synthase (FAS), acetyl CoA carboxylase (ACC), and elongase of very long chain fatty acids (ELOVL) did not show significant changes either in the embryonic stage or at hatching day 20 (P>0.05). However, there were significant changes in the gene expression and enzyme activities of TC, LDL-C and FAS at post-hatching stages (P≤0.05). These results may indicate that the thermal treatment has less influence on lipid metabolism in the embryonic stage but has a much stronger effect in the post-hatching stage.     

Metabolic and organ mass responses to selection for high growth rates in the domestic chicken (Gallus domesticus)

Evolutionary hypotheses suggest that higher rates of postembryonic development in birds should either lower the resting metabolic rate (RMR) in a trade-off between the costs of growth and maintenance or increase RMR because of a buildup of metabolic machinery. Furthermore, some suggest that higher rates of postembryonic development in birds should reduce peak metabolic rate (PMR) through delayed tissue maturation and/or an increased energy allocation to organ growth. We studied this by comparing metabolic rates and organ sizes of fast-growing meat-type chickens (broilers) with those of birds from a laying strain, which grow much slower. During the first week of life, despite growing six times faster, the RMR of the broiler chickens was lower than that of birds of the laying strain. The difference between strains in RMR disappeared thereafter, even though broilers continued to grow twice as fast as layers. The differences between strains in growth rate during the first week after hatching were not reflected in similar differences in the relative masses of the heart, liver, and small intestine. However, broilers had heavier intestines once they reached a body mass of 80 g. In contrast, broilers had relatively smaller brains than did layers. There was a positive correlation, over both strains, between RMR and the masses of leg muscles, intestine, and liver. Furthermore, despite delayed maturation of muscle tissue, broilers exhibited significantly higher PMR. We hypothesize that a balance between the larger relative muscle mass but lower muscle maturation level explains this high PMR. Another correlation, between leg muscle mass and PMR, partly explained the positive correlation between RMR and PMR.     

Endothermic heart rate response in broiler and White Leghorn chicks (Gallus gallus domesticus) during the first two days of post-hatch life

The embryonic modal value of heart rate (MHR) differs between broiler and White Leghorn chickens, but the initial development of cholinergic chronotropic control of embryonic heart rate (HR) does not. Thus, we hypothesized that hatchling MHR should also differ between broiler and White Leghorn strains, while the development of a physiological regulation, such as the endothermic HR response, should not be different between hatchlings of the two strains. To test this, we measured the response of HR and cloaca temperature (Tb) to alteration of ambient temperature (Ta); i.e., 35 degrees C-25 degrees C-35 degrees C, in four groups of hatchlings on Days 0 and 1 post-hatch. Fertile eggs of both strains with similar mass were incubated simultaneously in the same incubator. Eggs of broiler chickens hatched approximately 7 h earlier than White Leghorn chicken eggs. Chick mass at hatching was identical in both strains, but diverged during 2 days after hatching. Tb measured at the initial Ta of 35 degrees C was identical in both strains. MHR at the same Ta was approximately 30 bpm lower in broiler chicks than in White Leghorn chicks, but the difference was reversed to that observed in the embryos. The endothermic HR response was advanced by approximately 1 day in broiler chicks compared with White Leghorn chicks. As a result, eggs of similar mass in both strains produced chicks with similar mass and Tb at hatching, but during 2 days of post-hatch life their masses diverged and regulation of the endothermic HR response developed earlier in broiler than in White Leghorn hatchlings. This physiological heterochrony between strains is most likely due to genetic selection for fast growth in broiler chickens.     

Change in hepatic and plasma bile acid contents and its regulatory gene expression in the chicken embryo

To investigate changes in bile acid biosynthesis in chicken (Gallus gallus) during embryonic stages, we studied the contribution of hepatic and plasma total bile acid levels, mRNA expression of cholesterol 7 alpha-hydroxylase (CYP7A1), and the expression of its regulatory genes in two embryo models (i.e., broilers and layers) differing in lipid metabolism. Total bile acid levels in plasma and liver were low during embryonic stages, as well as expression of CYP7A1. At hatch (P0), hepatic and plasma total bile acid levels and CYP7A1 mRNA expression in liver were markedly increased in both models. The hepatic mRNA expression of liver X receptor (LXR)alpha, a regulator of CYP7A1 gene expression gradually decreased with developmental stages of both broilers and layers. The hepatic mRNA expression of farnesoid X receptor (FXR), a repressor of CYP7A1 gene expression, also decreased with embryonic development. The present results showed that the mRNA expression of CYP7A1 and synthesis of bile acids was low in embryonic stages, suggesting that FXR might be a key regulator of CYP7A1 gene expression in the chicken embryo.     

Lipid mediator production by post-implantation rat embryos in vitro

The production of inflammatory lipid mediators by post-implantation rodent embryos was examined in this study. Explanted day 10 rat embryos, either intact or after homogenization, were cultured for 3 hr in vitro and the resulting culture medium and embryonic tissue were assessed for eicosanoids and platelet-activating factor (PAF). The rank order of cyclooxygenase arachidonate products produced by intact embryos was as follows: 6-keto-PGF1 alpha much greater than congruent to PGF2 alpha congruent to TXB2. No lipoxygenase products of arachidonic acid metabolism were detected by either high performance liquid chromatography or radioimmunoassay. PAF production was detectable in embryonic cultures. Homogenization of rat embryos prior to in vitro culture enhanced eicosanoid and PAF production from 2.1-6.9 fold over intact embryos. These findings demonstrate the extent of lipid metabolism by early post-implantation rat embryos and support the concept that potent lipid mediators of inflammation generated by the conceptus may play a role in both the initiation and maintenance of pregnancy.     

Patterns of ribosomal gene variation in elite commercial chicken pure line populations

The nucleolus organizer region (NOR) encodes the tandemly repeated 18S, 5.8S and 28S ribosomal (r) RNA genes. The NORs of broiler and layer commercial chicken pure lines were studied to establish the type and extent of genetic variation at this important locus. The parameters studied were gene copy number, repeat size, and diversity of NOR-types. The populations were organized into three groups for analysis including brown-egg broiler (13 lines), brown-egg layer (six lines), and white-egg layer (eight lines). The ribosomal gene copy number average of the white-egg layer populations was significantly lower (329 genes) than that of the brown-egg layers (372 genes); the brown-egg broiler ribosomal gene average was intermediate (350 genes). The white-egg layer populations exhibited a ribosomal repeat unit average size of 36 kb, significantly different from the brown-egg layer and brown-egg broiler average repeat unit size of 32.5 and 33.9 kb, respectively. NOR array size was similar among the three groups (6 mb). The brown-egg broiler populations exhibited polymorphic NOR patterns, intra- and interline, whereas the white-egg layer populations were essentially monomorphic for NOR-type; brown-egg layers exhibited an intermediate level of NOR diversity. Some NOR array characteristics may be a function of breed origin as brown-egg commercial populations, both broilers and layers, have similar breed origins and exhibited similarities for predominant repeat unit size as compared with white-egg layer populations. However, the finding that brown-egg broiler lines typically exhibit a greater number of segregating NOR-types than brown-egg layer lines suggests that the selection schemes of broiler vs. layer pure line populations may also have influenced the degree of variation at this gene complex.     

Polypeptide composition and organization of the sea urchin extraembryonic hyaline layer.

The protein composition and organization of the sea urchin extraembryonic hyaline layer was examined. Hyalin and a polypeptide of 45 kilodaltons (kDa) were present in hyaline layers isolated from 1-h-old embryos through to the pluteus larva stage. In contrast, several polypeptide species ranging in size from 175 to 32 kDa either decreased in amount or disappeared from the layer as embryonic development proceeded. Concomitant with the changes in composition, hyaline layers became progressively more refractory to dissolution by washing in Ca2+, Mg2(+)-free seawater. Incubation of intact layers, isolated from 1-h-old embryos, with proteinase K resulted in the selective digestion of hyalin and was accompanied by release of the 45-kDa polypeptide from the layers. Washing intact layers in 20 mM Tris (pH 8.0) also resulted in the selective removal of hyalin and the 45-kDa polypeptide. The Ca2(+)-precipitable protein hyalin, alone among the hyaline layer polypeptides, bound the Ca2(+)-antagonist ruthenium red. These results suggest a structural organization within the hyaline layer that is both heterogenous and dynamic throughout embryonic development.     

Muscle growth and protein degradation during early development in chicks of fast and slow growing strains

1. Growth of breast and leg muscles and excretion of N tau methyl histidine in layer (slow growing) and broiler (fast growing) chicks were measured at five time intervals between 2 and 33 days of age. 2. The results indicate that muscles of the broiler chick grow faster than in layer chicks and that breast muscles of both strains grow faster than leg muscles in the first 2 weeks after hatching. 3. N tau methyl histidine excretion by layer chicks is higher than that by broilers relative to body weight, musculature and relative maturity at all ages examined. 4. The results suggest that faster growth of muscles is accompanied by a lower rate of protein degradation although at ages of less than 2 weeks differences in protein synthesis rates may also contribute to muscle growth.     

Comparative proteomics and phosphoproteomics analyses of DHEA-induced on hepatic lipid metabolism in broiler chickens

Dehydroepiandrosterone (DHEA) is a precursor of the adrenocorticosteroid hormones that are common to all animals, including poultry. The study described herein was undertaken to investigate the effect of DHEA on lipid metabolism in broiler chickens during embryonic development and to determine the regulatory mechanisms involved in its physiological action. Treatment group eggs were injected with 50 mg DHEA diluted in 50 μL dimethyl sulfoxide (DMSO) per kg, while control group eggs (arbor acres [AA] fertilized) were injected with 50 μL DMSO per kg prior to incubation. Liver samples were collected on days 9, 14 and 19 of embryonic development as well as at hatching. Extracted proteins were analyzed by two dimensional gel electrophoresis (2-DE) in combination with western blotting for specific anti-phosphotyrosine. The differential spots were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) or MALDI-TOF-TOF-MS. Peptide mass fingerprinting (PMF) of the differentially-expressed proteins were performed using the MASCOT, Prospector or proFound server. Thirty-seven proteins and twenty-two tyrosine phosphorylation proteins were successfully identified. All 37 proteins and 22 tyrosine phosphorylation proteins exhibited a significant volume difference from the control group. These results demonstrated that DHEA increased the expression and level of tyrosine phosphorylation and sulfotransferase proteins in broilers (at pI 5.9), therefore promoting the biotransformation of DHEA. The expression of apolipoproteinA-I was increased in the DHEA treatment group, which facilitated the conversion of cholesterol to cholesterol esters. Also, DHEA increased the expression of peroxiredoxin-6 and its tyrosine phosphorylation protein levels, thus enhancing its anti-oxidative activity. Furthermore, pyruvate dehydrogenase expression was decreased and the level of its tyrosine phosphorylation proteins increased in the DHEA treatment group. Take together, those data indicate that DHEA reduces the supply of acetyl-CoA by inhibiting the activity of its target enzyme (i.e. pyruvate dehydrogenase), thus affecting both protein synthesis and phosphorylation level and decreasing fat deposition in broiler chickens during embryonic development, which could reflect a physiologically-relevant DHEA fat-reduction mechanism in the broiler chicken.     

Development of interspecies cloned embryos in yak and dog

Interspecies nuclear transfer (NT) could be an alternative to replicate animals when supply of recipient oocytes is limited or in vitro embryo production systems are incomplete. In the present study, embryonic development was assessed following interspecies NT of donor cumulus cells derived from yak and dog into the recipient ooplasm of domestic cow. The percentages of fusion and subsequent embryo development to the eight-cell stage of interspecies NT embryos were comparable to those of intraspecies NT embryos (cow-cow NT embryos). The percentage of development to blastocysts was significantly lower (p < 0.05) in yak-cow NT embryos than that in cow-cow NT embryos (10.9% vs. 39.8%). In dog-cow NT embryos, only one embryo (0.4%) developed to the blastocyst stage. These results indicate that interspecies NT embryos possess equally developmental competence to the eight-cell stage as intraspecies NT embryos, but the development to blastocysts is very low when dog somatic cells are used as the donor nuclei.     

Avian embryonic thermoregulation: role of Q10 in interpretation of endothermic reactions

1. Incubated chicken eggs (D14 to D21) were placed separately in transparent acrylic glass chambers which were immersed in a 37.5°C water bath for 3 h. The chambers were then moved for 3 h to another water bath controlled at 34.5°C. Oxygen consumption and temperature of the allantoic fluid (T_af) were measured at 5-min intervals for the whole experiment using an oxygen analyzer and CrNi–Ni-thermocouples, respectively. Heat production (HP) was calculated, using an assumed RQ of 0.72.

2. At 37.5°C the relationship between HP and embryonic age follows a sigmoid curve. Between D18 (HP 7.25 J g⁻¹ h; 2.01 W kg⁻¹) and D19 (HP 7.21 J g⁻¹ h⁻¹; 2.00 W kg⁻¹) this function had a plateau phase with a duration of about 24 h.

3. During the cooling process, HP decreased continuously and the relationship between T_a and HP could be described by an exponential function. From the results, it was possible to calculate the relationships between T_af, as a measure of body core temperature, and Q₁₀; the lower the T_af the higher the Q₁₀.

4. Because the actual measured HP is the result of the negative effect of Q₁₀ on HP and the stimulating influence of the CNS-generated HP, a Q₁₀ of more than 2.0 demonstrates the absence of endothermy. Chicken embryos aged between 14 and 21 d have a Q₁₀ of less than 2.0 at body temperatures (T_af) between 34 and 30°C. It is postulated that in chicken embryos of this age endothermic reactions may occur.

5. The Q₁₀-method is suitable for investigating the prenatal development of endothermic reactions in avian embryos.     

Why are young broiler chickens fatter than layer-strain chicks?

1. The abdominal fat pads of 5 week-old broiler and layer chicks incorporated 6.0 and 3.9% of intravenously-injected 14C-labelled very low density lipoproteins respectively. 2. These proportions of total plasma lipoprotein flux were sufficient to account for about 65-70% of the rate of fat deposition in broilers, but were more than 4-fold greater than that the rate of fat deposition in layers. 3. [14C]Palmitate taken up into adipose tissue of layer chicks had a t1/2 of 2-3 days. 4. There was no significant turnover of adipose tissue triglycerides in broilers and this appears to be a major reason for their relative fatness.     

Morphological features of lipid droplet transition during porcine oocyte fertilisation and early embryonic development to blastocyst in vivo and in vitro

Lipid content in mammalian oocytes or embryos differs among species, with bovine and porcine oocytes and embryos showing large cytoplasmic droplets. These droplets are considered to play important roles in energy metabolism during oocyte maturation, fertilisation and early embryonic development, and also in the freezing ability of oocytes or embryos; however, their detailed distribution or function is not well understood. In the present study, changes in the distribution and morphology of porcine lipid droplets during in vivo and in vitro fertilisation, in contrast to parthenogenetic oocyte activation, as well as during their development to blastocyst stage, were evaluated by transmission electron microscopy (TEM). The analysis of semi-thin and ultra-thin sections by TEM showed conspicuous, large, electron-dense lipid droplets, sometimes associated with mitochondrial aggregates in the oocytes, irrespective of whether the oocytes had been matured in vivo or in vitro. Immediately after sperm penetration, the electron density of the lipid droplets was lost in both the in vivo and in vitro oocytes, the reduction being most evident in the oocytes developed in vitro. Density was restored in the pronculear oocytes, fully in the in vivo specimens but only partially in the in vitro ones. The number and size of the droplets seemed, however, to have decreased. At 2- to 4-cell and blastocyst stages, the features of the lipid droplets were almost the same as those of pronuclear oocytes, showing a homogeneous or saturated density in the in vivo embryos but a marbled or partially saturated appearance in the in vitro embryos. In vitro matured oocytes undergoing parthenogenesis had lipid droplets that resembled those of fertilised oocytes until the pronuclear stage. Overall, results indicate variations in both the morphology and amount of cytoplasmic lipid droplets during porcine oocyte maturation, fertilisation and early embryo development as well as differences between in vivo and in vitro development, suggesting both different energy status during preimplantation development in pigs and substantial differences between in vitro and in vivo development.     

Ultrastructural studies of epidermis keratinization in grass snake embryos Natrix natrix L. (Lepidosauria, Serpentes) during late embryogenesis

The changes and biochemical features of the epidermis that accompany the differentiation and embryonic shedding complex formation in grass snake Natrix natrix L. embryos were studied ultrastructurally and immunocytochemically with two panels of antibodies (AE1, AE3, AE1/AE3; anti-cytokeratin, pan mixture, Lu-5 and PCK-26). All observed changes in the ultrastructure of the cells forming the epidermal layers were associated with the physiological changes that occurred in the embryonic epidermis, such as changing of the manner of nutrition and keratinization leading to the embryonic shedding complex formation. The layers that originated first (basal, outer and inner periderm and clear layer) differentiated very early and rapidly. Rapid differentiation was also observed in the layers that are very important for the functioning of the epidermis in Natrix embryos (oberhäutchen and beta-layers). They started to differentiate at developmental stage IX, and then fused and formed the embryonic shedding complex at developmental stage XI. During the embryonic development of the grass snake the smallest changes appeared in the ultrastructure of the cells in the mesos and alpha-layers because they perform supplementary functions in the process of embryonic molting. They were undifferentiated until the end of embryonic development and started to differentiate just before the first adult molting. AE1/AE3, anti-cytokeratin, pan mixture, Lu-5 and PCK-26 antibodies immunolabeled clear layer, oberhäutchen and beta-layers at the latest phase of developmental stage XI. It should be noted that these antibodies did not immunolabel the alpha-layer until hatching. The presence of alpha-keratin immunolabeling in layers that were keratinized, particularly in the oberhäutchen and beta-layers in embryos, indicated that they were not as hard as in fully mature individuals.