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.

Tsukushi cooperates with VG1 to induce primitive streak and Hensen's node formation in the chick embryo

Three classes of signaling molecule, VG1, WNT and BMP, play crucial roles in axis formation in the chick embryo. Although VG1 and WNT signals have a pivotal function in inducing the primitive streak and Hensen's node in the embryo midline, their action is complemented by that of BMP antagonists that protect the prospective axial tissue from the inhibitory influence of BMPs secreted from the periphery. We have previously reported that a secreted factor, chick Tsukushi (TSK), is expressed in the primitive streak and Hensen's node, where it works as a BMP antagonist. Here, we describe a new crucial function for TSK in promoting formation of the primitive streak and Hensen's node by positively regulating VG1 activity. We provide evidence that TSK directly binds VG1 in vitro, and that TSK and VG1 functionally interact in axis formation, as shown by biological assays performed in chick and Xenopus embryos. Furthermore, we show that alternative splicing of TSK RNA leads to the formation of two isoforms (TSKA, originally designated as TSK, and TSKB) that differ in their C-terminal region. Biochemical and biological assays indicate that TSKB is a much weaker BMP antagonist than TSKA, although both isoforms efficiently interact with VG1. Remarkably, although both TSKA and TSKB are expressed throughout the early extending primitive streak, their expression patterns diverge during gastrulation. TSKA expression concentrates in Hensen's node, a well-known source of anti-BMP signals, whereas TSKB accumulates in the middle primitive streak (MPS), a region known to work as a node-inducing center where VG1 expression is also specifically localized. Loss-of-function experiments demonstrate that TSKB, but not TSKA, function is required in the MPS for induction of Hensen's node. Taken together, these results indicate that TSK isoforms play a crucial role in chick axis formation by locally modulating VG1 and BMP activities during gastrulation.

Effect of Flock Age, Cessation of Egg Turning, and Turning Frequency Through the Second Week of Incubation on Hatchability of Broiler Hatching Eggs

Hatching eggs from commercial broiler breeder flocks at 34 and 37 wk of age (young) and at 59 and 61 wk of age (old) were stored for 2 d at 18 degrees C and 75% RH and then subjected to turning frequencies of 24 or 96 times daily up to 8, 10, 12, or 14 d of incubation at standard conditions to determine if an increased turning frequency would facilitate an early cessation of turning. Turning was discontinued after the respective days were completed. Eggs remained in setter trays until combined at 18 d to complete hatching in a single machine. The young flocks exhibited significantly better fertile hatchability, as expected, but there was no overall effect due to differences in cessation of turning from 8 to 14 d of incubation (range 88.9 to 89.2%). However, turning 96 times daily produced significantly better fertile hatchability that was largely due to a significant interaction of flock age and turning frequency; the beneficial effect of increased turning frequency, largely reduced late-embryonic mortality, was more evident in the eggs from the older flocks.

Effect of Egg Turning Angle and Frequency During Incubation on Hatchability and Incidence of Unhatched Broiler Embryos with Head in the Small End of the Egg

The effect of turning angle (from vertical) and the interaction with turning frequency during incubation on fertile hatchability, embryonic mortality, and the incidence of embryos with head in the small end of the egg (malpositioned) was studied in 2 experiments comprising 2 trials each to determine if a turning angle of less than 45 degrees could be successful. Hatching eggs from commercial broiler breeder flocks from 55 to 61 wk of age were utilized, and turning was for 18 d. Eggs were subjected to turning angles of 35, 40, or 45 degrees, with a turning frequency of 24 times daily (24x) in Experiment 1. Turning angle had no effect on fertile hatchability. However, the incidence of separately enumerated, malpositioned embryos was increased by the 35 degrees angle, compared with both the 40 and 45 degrees angles in Experiment 1. Eggs were subjected to turning angles (from vertical) of 35 degrees, with a turning frequency of either 24x or 96x daily, or 45 degrees, with 24x turning in the 2 trials of Experiment 2. Turning angle and frequency had no effect on fertile hatchability or embryonic mortality, but the incidence of separately enumerated, malpositioned embryos was increased by the 35 degrees angle with 24x turning, compared with the 35 degrees angle with 96x turning, and the 45 degrees angle, with 24x turning, in Experiment 2. These data demonstrated that the incidence of malpositioned embryos was increased by a reduced turning angle, but that this effect was ameliorated by a concomitant increase in turning frequency.

[Multifunctional morphology of the chick chorioallantoic membrane]

The chicken chorioallantoic membrane is assessed between days 7 and 20 of incubation using light and electron microscopy with morphometric analysis. The completion of its formation by the middle of embryogenesis is observed, after that a rapid increase in the embryo body mass continues. The bloodstream combines chorionic epithelium, mesoderm, and allantoic epithelium into the single multifunctional organ. The ordered antiparallel arrangement of afferent and efferent vessels within the mesoderm as well as their specialized endothelium assist in partial blood fluid filtration into the interstitium. The unique structure of the capillary network within and over the chorionic epithelium that provide for the effective gas exchange is depicted. It is revealed that the ultrastuctural specialization of the chorionic epithelial cells through which an active calcium transport from the eggshell takes place. The ultrastructure peculiarities of the allantoic epithelium concerning the water-salt balance maintaining in the growing embryo, are discussed.

Upregulation of chicken p15INK4b at senescence and in the developing brain

In mammalian cells, products of the INK4a-ARF locus play major roles in senescence and tumour suppression in different contexts, whereas the adjacent INK4b gene is more generally associated with transforming growth factor β (TGF-β)-mediated growth arrest. As the chicken genome does not encode an equivalent of INK4a, we asked whether INK4b and/or ARF contribute to replicative senescence in chicken cells. In chicken embryo fibroblasts (CEFs), INK4b levels increase substantially at senescence and the gene is transcriptionally silenced in two spontaneously immortalised chicken cell lines. By contrast, ARF levels are unaffected by prolonged culture or immortalisation. These expression patterns resemble the behaviour of INK4a and ARF in human fibroblasts. However, short-hairpin RNA (shRNA)-mediated knockdown of chicken INK4b or ARF provides only modest lifespan extension, suggesting that other factors contribute to senescence in CEFs. As well as underscoring the importance of the INK4b-ARF-INK4a locus in senescence, these findings imply that the encoded products have assumed different roles in different evolutionary niches. Although ARF RNA is not detectable in early chicken embryos, the INK4b transcript is expressed in the roof-plate of the developing hind-brain, consistent with a role in limiting cell proliferation.

The Effects of Suboptimal Eggshell Temperature During Incubation on Broiler Chick Quality, Live Performance, and Further Processing Yield

Different incubation conditions can cause eggshell temperature (EST) to deviate from optimum. Two experiments were performed to determine the effect of low EST at the start of incubation and high EST at the end of incubation on hatchability, chick quality, 6-wk live performance, and breast meat yield of broiler chickens. In each experiment, 1,800 eggs from a single flock were divided and set into 2 setters. From 0 to 10 d of incubation, one setter was set to attain an EST of 36.6 degrees C (considered low), whereas the other was set to 37.8 degrees C (the control temperature). Using an infrared thermometer, EST was measured daily on a sample of eggs to ensure treatment intentions. On d 11 of incubation, the temperature of the low EST setter was increased to 37.8 degrees C in synchrony with the other setter until transfer. On d 18 of incubation, eggs from both setters were combined into 2 equal groups and transferred to hatchers. The EST in one hatcher was set to 37.8 degrees C (control) and in the other to 39.5 degrees C (considered high) until 21 d of incubation. Hatched males were placed in battery cages (Experiment 1) or floor pens (Experiment 2) and reared on common feeds to 1 or 6 wk of age, respectively. Low EST in the first 10 d of incubation reduced hatchability, increased BW and chick yield, and reduced 1-wk gain compared with the control EST. Throughout rearing, BW was reduced for low EST chicks compared with control EST chicks; consequently, carcass, fillet, and tender weights were also reduced. High EST in the hatcher increased hatchability, and reduced BW, chick yield, and 1-wk gain compared with control EST in the hatcher. By 3 wk of age, there was no difference in BW between chicks in high EST and control EST treatments. Subsequent carcass and processing yields were also similar. Incubation at the control EST of 37.8 degrees C, particularly from 0 to 10 d, resulted in the best performance overall.

At least one YMHCI molecule in the chicken is alloimmunogenic and dynamically expressed on spleen cells during development

Transcriptionally active, MHC class I (MHCI) loci are located in two separate polymorphic genomic regions in the chicken called B and Y. The YMHCI gene sequences encode molecules with uncommon substitutions in the antigen-binding region indicating that YMHCI molecules are likely unique and may bind a specialized form of antigen distinct from that of other antigen-binding MHCI molecules. To learn whether YMHCI gene expression results in the production of alloantigens at the cell surface, we immunized 15I(5) x 7(2) : chickens using syngeneic RP9 cells expressing transduced YF1w*7.1, a potentially alloimmunogenic YMHCI allele from the Y7 haplotype present in line C. The resulting antisera show that YF1w*7.1 MHCI molecules are immunogenic and expressed on the surfaces of cells in blood and spleen of line C chickens. Virtually all CD3+, CD4+, and CD8+ cells circulating in line C blood are positive, as are BU1+ cells. The YF1w*7.1 MHCI allele is dynamically expressed at levels comparable to but transcriptionally independent of classical BMHCI on erythrocytes, lymphocytes, granulocytes, monocytes, and thrombocytes within the spleen pre- and post-hatching. The antisera react with cells from two among four haplotypes segregating in closed populations of lines N and P. YMHCI shares features associated with both classical and non-classical MHCI. It is becoming increasingly likely that YMHCI has a fundamental role in avian immunity and thereby needs to be included in the growing spectrum of functionally active, diverse MHCI molecules no longer adequately described by the classical/non-classical dichotomy.

Cloning and expression analysis of androgen receptor gene in chicken embryogenesis

We cloned a full-length androgen receptor (AR) cDNA from chicken (Gallus gallus) gonads. The cDNA sequence has an open reading frame of 2109 bp encoding 703 amino acids. The chicken AR (cAR) shares high homology with ARs from other species in its amino acid sequences, in particular DNA binding domain (DBD) and ligand binding domain (LBD). RT-PCR analysis revealed that cAR mRNA is expressed in several embryonic tissues of both sexes, and relatively higher expression was observed in left ovary compared with testis. The immunoreactive signal of AR was co-localized within the ovarian cell nucleus, while such nuclear localization was not detected in those of testis. To get insight on the possible role of androgen-AR signaling during gonadal development, non-steroidal AR antagonist, flutamide, was administrated in ovo. The treatment induced the disorganization of sex cords in ovarian cortex at day 12 of incubation. The effect was restored by testosterone co-treatment, implying the possibility that AR mediated signaling may be involved in ovarian morphogenesis. Furthermore, co-treatment of flutamide with estradiol-17beta (E2) also restored the phenotype, suggesting androgen-AR signaling might activate aromatase expression that is necessary for estrogen synthesis. These findings suggest androgen-AR signaling might contribute to chicken embryonic ovarian development.

Survivorship and Mortality Implications of Developmental 670-nm Phototherapy: Dioxin Co-exposure

OBJECTIVE

We assessed the effect of 670-nm light therapy on dioxin-induced embryonic mortality in chickens (Gallus gallus).

BACKGROUND DATA

Developmental photobiomodulation using 670-nm light-emitting diode (LED) arrays improves hatching success and increases body size in hatchling chickens. Photobiomodulation also stimulates signaling pathways resulting in improved energy metabolism, antioxidant production and cell survival. Dioxin causes embryonic mortality, including increases in the frequency of chicken embryos that pip but can't go to hatch. We hypothesized that 670-nm LED therapy would attenuate dioxin-induced embryo mortality.

METHODS

Fertile chicken eggs were injected with control or 2, 20, or 200 ppt 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin) prior to the start of incubation. Half of the eggs in each dose group were treated once per day from embryonic days 0-20 with 670-nm LED light at a fluence of 4 J/cm(2). In ovo survival and hatching success were compared between dose groups and LED treatment.

RESULTS

LED therapy decreased the embryonic mortality rate by 41%, resulting in increased embryonic survival and improved hatching success in eggs exposed to 200 ppt dioxin. However, at sub-lethal dioxin concentrations and in oil-treated controls, LED therapy slightly increased mortality.

CONCLUSION

Overall survivorship and hatching success of chicks developmentally exposed to dioxin concentrations above the lethality threshold (>100 ppt TCDD) is improved by 670-nm LED treatment administered throughout the gestation period, but the relationship may be complicated by an LED-oil interaction.

Proteomic analysis of the Gallus gallus embryo at stage-29 of development

The chicken (Gallus gallus) is one of the primary models for embryological and developmental studies. In order to begin to understand the molecular mechanisms underlying the normal and abnormal development of the chicken, we used 2-DE to construct a whole-embryo proteome map. Proteins were separated by IEF on IPG strips, and by 11% SDS-PAGE) gels. Protein identification was performed by means of PMF with MALDI-TOF-MS. In all, 105 protein spots were identified, 35 of them implicated in embryo development, 10 related with some diseases, and 16, finally, being proteins that have never been identified, purified or characterized in the chicken before. This map will be updated continuously and will serve as a reference database for investigators, studying changes at the protein level under different physiological conditions.

Toxicity of a pendimethalin containing herbicide formulation and three heavy metals in chicken embryos

The toxic effects of a widely used herbicide (Stomp 330 containing 33% pendimethalin as active ingredient) applied alone or in combination with three heavy elements (copper sulphate, cadmium sulphate and lead acetate) modelling the heavy metal load of the environment were studied on chicken embryos with injection treatment. The treatment was done on day 0 of incubation. Solutions and emulsions of different concentrations were made from the test materials and injected in 0.1 ml volume into the air space of eggs. The macroscopical evaluations were done on day 19 of the incubation. Summarizing the findings, it can be established that the individual administration of the 33% pendimethalin containing herbicide formulation was less toxic compared to the control group than the simultaneous administration of the pesticide and heavy elements. As compared with each other the results from the combined administrations of the 33% pendimethalin containing herbicide formulation and heavy elements the simultaneous administration of cadmium and the herbicide caused the highest embryomortality while the incidence of developmental anomalies were the highest in the interaction study of the copper and the pesticide.

Teratogenicity testing of a 2,4-D containing herbicide formulation and three heavy metals in chicken embryos

The toxic effects of a widely used herbicide (Dikamin D containing 72% 2,4-D-amine Na as active ingredient) applied alone or in combination with three heavy elements (copper sulphate, cadmium sulphate and lead acetate) modelling the heavy metal load of the environment were studied on chicken embryos with injection treatment. The treatment was done on day 0 of incubation. Solutions and emulsions of different concentrations were made from the test materials and injected in 0.1 ml volume into the air space of eggs. The macroscopical evaluations were done on day 19 of the incubation. Summarizing the findings, it can be established that the individual administration of the 72% 2,4-D containing herbicide formulation was less toxic compared to the control group than the simultaneous administration of the pesticide and heavy elements. As compared with each other the results from the combined administrations of the 72% 2,4-D containing herbicide formulation and heavy elements the simultaneous administration of cadmium and the herbicide caused the highest embryomortality while the incidence of developmental anomalies were the highest in the interaction study of the copper and the pesticide.

Culture of chicken embryos in surrogate eggshells

The chick embryo is a classical model to study embryonic development. However, most researchers have not studied the effect of embryonic manipulation on chick hatchability. The objective of this study was to determine the effect of egg orientation and type of sealing film on the hatchability of cultured embryos. Windows were made in the small end of recipient surrogate chicken eggshells, and donor embryos were placed into the recipient eggshell for the first 3 d of incubation. Survival over the first 3 d was maximized (P < 0.05) when windowed eggs sealed with Saran Wrap were positioned with the window-end down compared with window-end up. Three-day-old cultured embryos were transferred into recipient turkey eggshells, sealed with cling film, and cultured until hatch. Water weight loss of the surrogate eggshell cultures regardless of cling film type was not significantly different from control intact eggs. The embryos cultured in turkey eggshells and sealed with Handi Wrap exhibited higher hatchability (75% +/- 10.2%) than cultures sealed with Saran Wrap (45.2% +/- 13.8%). Hatchability of control intact eggs (86.4% +/- 5.3%) was not significantly (P > 0.05) different from the hatchability of eggs sealed with Handi Wrap, which suggested that Handi Wrap was an excellent sealant for chick embryos cultured after 3 d of incubation.

Changes in chicken intestinal zinc exporter mRNA expression and small intestinal functionality following intra-amniotic zinc-methionine administration

A 303-bp cDNA of intestinal zinc exporter (ZnT1) was isolated from chicken jejunum by reverse transcriptase-polymerase chain reaction and sequenced, and showed 42% homology to Homo sapiens and Rattus novergicus intestinal ZnT1 genes. This specific probe was used to examine the effect of zinc-methionine (ZnMet) administration on the mRNA expression of ZnT1 and on small intestinal development and functionality. In this study, ZnMet was injected into the naturally consumed amniotic fluid of 17-day-old chicken embryos. The ZnT1 gene showed an approximately 200% increase in its mRNA levels from 48 h post-ZnMet injection, as compared to the control. An analysis of the gene expression of the brush-border enzymes and transporters showed increased mRNA expression of sucrase isomaltase, leucine-aminopeptidase, sodium-glucose cotransporter and Na+K+ATPase transporter (Na+K+ATPase) from 48 h post-ZnMet injection, in comparison to controls. Significant increases (P<.05) in the biochemical activity of the brush-border enzymes and transporters, and in jejunal villus surface area were detected from day of hatch (96 h post-ZnMet injection) as compared to controls. These results suggest that ZnMet administration into prenatal intestine via injection into the amniotic fluid enhances intestinal development and improves its functionality.

Comparison of three lines of broilers differing in ascites susceptibility or growth rate. 2. Egg weight loss, gas pressures, embryonic heat production, and physiological hormone levels

Ascites is a metabolic disorder that accounts for over 25% of overall mortality in the broiler industry. This disorder is manifested between wk 5 and 6 posthatch, but there are previous indications that predisposition may be identified during embryonic development. In this current study, we determined embryonic physiological and metabolic parameters that may be associated with ascites predisposition. For this purpose, we used broiler eggs from 3 lines that differed in ascites sensitivity. These included an ascites-sensitive dam line (DAS), an ascites-resistant dam line (DAR), and an ascites-sensitive sire line (SASL). Eggs were incubated for 21 d under standard conditions. The following parameters were measured during incubation: egg weights at setting, egg weight losses at 18 d, embryo body weights and embryo heart weights throughout development, air cell partial gas pressures (pCO2 and pO2) levels at d 18 and at internal pipping (IP); plasma triiodothyronine, thyroxine, and corticosterone levels at d 18, IP, and hatch; heat production from d 17 until hatch, hematocrit values at hatch, and posthatch growth rate to 7 d along with hematocrit values. The data obtained revealed that selection for ascites sensitivity or rapid growth rate had no consistent influence on some of these parameters such that they could be wholly associated with ascites sensitivity for predictive purposes. Whereas differences in embryonic developmental patterns were apparent throughout embryonic development, these differences in physiological and metabolic parameters may be due partly to genetic differences unrelated to ascites sensitivity.

Comparative genomics of the Hlx homeobox gene and protein: conservation of structure and expression from fish to mammals

Hlx is a homeobox transcription factor gene that is expressed in intestinal and hepatic mesenchyme of the developing mouse embryo and is essential for normal intestinal and hepatic development. Because of the morphological and molecular similarities in the development of the digestive system across species, we hypothesized that the Hlx gene and protein sequences and expression patterns would be conserved among vertebrates. Comparison of the Hlx gene orthologues of human, chimpanzee, mouse, rat, pufferfish (Fugu) and zebrafish demonstrates that these six genes share an identical organization with four exons and three introns. Comparison of the inferred Hlx protein sequences from these and three additional species (chick, Spanish ribbed newt and rainbow trout) reveals significant sequence identity, with identical homeodomains. The expression of Hlx in the mesenchyme of developing chick embryos is highly similar to that of mouse. Fugu Hlx is expressed in a tissue-specific manner that is similar though not identical to that of mouse, suggesting a conservation of Hlx function between mammals and birds. The mammalian and fish Hlx genes share a putative 5' upstream enhancer as well as an inverted repeat containing CCAAT boxes on opposite strands that we have previously shown to be important for mouse Hlx gene expression. These results suggest that the function of Hlx and the mechanisms regulating its expression are highly conserved in mammals, birds, amphibians and fish.

Effect of eggshell temperature during incubation on embryo development, hatchability, and posthatch development

An experiment was conducted to study the effects of different eggshell temperature (EST) profiles during incubation on embryo mortality, hatchability, and embryo development. Furthermore, chicks from different EST profiles were reared under low and high housing temperatures to investigate subsequent posthatch growth and rectal temperature. Two batches of eggs were used in this experiment. Hatching eggs were subjected to 36.7 or 37.8 degrees C EST during the first week, to 37.8 degrees C EST during the second week, and to 37.8 or 38.9 degrees C EST during the third week of incubation. Posthatch housing temperature decreased from 35 degrees C at d 1 to 30 degrees C at d 7 (high) or decreased from 30 degrees C at d 1 to 25 degrees C at d 7 (low). The difference between machine temperature and EST (DT) was used to illustrate the effect of EST on heat production during incubation. DT differed per batch, and was smallest when eggs were incubated at 36.7 degrees C instead of 37.8 degrees C during wk 1. High EST during wk 3 of incubation (38.9 degrees C instead of 37.8 degrees C) reduced DT only in batch 2. Embryo development was most retarded in eggs incubated at 36.7 degrees C EST compared with at 37.8 degrees C during the first week of incubation. However, highest hatchability and embryo development were always found when EST was maintained at 37.8 degrees C constantly throughout incubation. Chicks that hatched from eggs incubated at low EST during wk 1 of incubation had lower rectal temperature after hatching, especially under low housing temperatures, and this effect lasted until 7 d posthatch in batch 1. The highest rectal temperatures were always found in chicks incubated at 37.8 degrees C EST constantly throughout incubation. Eggs and chicks from different batches require different environmental conditions for optimal embryo development, hatchability, and posthatch growth. Rearing temperature and incubation conditions affect the ability of young chicks to maintain their rectal temperature during the first week posthatch.

Establishment of a chick embryo model for analyzing liver development and a search for candidate genes

The liver plays a crucial role in metabolism. There is considerable interest in how the liver develops, as such knowledge could prove of importance in regenerative medicine. However, our understanding of liver development remains somewhat limited. We have developed a model system using the chick embryo that is cost effective and is easy to manipulate experimentally. We performed four fundamental studies: (i) construction of an atlas of the developing chick liver; (ii) identification of differentiation marker genes in the developing chick embryo; (iii) development of germ-layer specific electroporation; and (iv) establishment of organ culture from the developing chick liver. Using this system, we have been able to demonstrate the functions of candidate genes within a shorter period and in a more cost-effective manner. In parallel with the establishment of this system, we examined the expression patterns of genes known to be required for organ development in the developing chick embryo in order to identify genes also involved in liver development. To date, we have found sixteen genes that are expressed in the developing chick liver (GELD, genes expressed in liver development). This knowledge will be fundamental to the establishment of the basic technology for engineering liver tissue in the future.

Twenty-five hydroxycholecalciferol as a cholecalciferol substitute in broiler breeder hen diets and its effect on the performance and general health of the progeny

An experiment was conducted with broiler breeder hens to determine the relative biological value of 25-hydroxycholecalciferol (25-OHD3) compared with cholecalciferol (vitamin D3) for hen-day egg production, hatchability, embryo mortality (early, 1 to 10 d of incubation, late, 11 to 21 d), and body ash of the progeny. The study was conducted with 73-to-90-wk-old molted Ross broiler breeder hens in an environment excluding ultraviolet light. A basal vitamin D3 deficient diet supplemented with 4 levels of vitamin D3 (0, 3,125, 12,500, and 50,000 ng/kg of diet) and 2 levels of 25-OHD3 (3,125 and 12,500 ng/kg of diet) was fed. The relative biological values of 25-OHD3 in comparison to vitamin D3, using slope ratio techniques, were 138, 133, 128, and 111% for hen-day egg production, hatchability, late embryo mortality, and body ash of the progeny,, respectively (average = 128%). When comparing 25-OHD3 against D3 at the 3,125 ng/kg level, the relative biological values were 209, 167, 400, and 108% for the same criteria, respectively (average = 221%). However, at the 12,500 ng/kg level no statistical differences between 25-OHD3 and D3 were observed (average = 108%). Four trials were conducted to determine the effect of the maternal diet on the performance and leg abnormalities of the hens' progeny. In experiment 1, no vitamin D was added to the corn-soybean meal basal diet fed to the chicks, and in experiments 2, 3, and 4 the basal diet was supplemented with 27.5 microg of D3/kg of diet. In the progeny study, the average relative biological value of 25-OHD3 at the 3,125 and 12,500 ng/kg levels were 115 and 101%, respectively. The potency of 25-OHD3 in relation to vitamin D3 depended on the level tested. When comparing vitamin D sources, 25-OHD3 had greater potency than D3 only at very low levels of supplementation.

Effects of vitamin D3 dietary supplementation of broiler breeder hens on the performance and bone abnormalities of the progeny

Six experiments were conducted using Ross x Ross chicks hatched from eggs laid by broiler breeder hens fed various levels of vitamin D3 (0 to 4,000 IU/kg of diet) to determine the effects of vitamin D3 level in the maternal diet on the performance and leg abnormalities of their progeny. Chicks hatched from eggs laid when hens were 27, 41, 29, 36, 45, and 52 wk of age were used in experiments 1, 2, 3, 4, 5, and 6, respectively. The studies were conducted in a ultraviolet (UV)-light-free environment. Experiments 1 and 2 were conducted as complete randomized designs with the maternal diets as the treatments, and experiments 3, 4, 5, and 6 were conducted as split plot designs, with vitamin D3 in the chick diets as the whole plot and vitamin D3 in the maternal diet as a subplot. Chicks in experiments 1 and 2 were fed a vitamin D3-deficient diet, whereas chicks in experiments 3 and 4 were fed 4 levels of vitamin D3 (0 to 400 IU/kg of diet), and chicks in experiments 5 and 6 were fed 6 levels of vitamin D3 (0 to 3,200 IU/kg of D3). The highest body weight gains and tibia ash were observed in chicks hatched from hens fed the highest levels of vitamin D3 in all experiments. Reductions in the incidence of Ca rickets were observed in experiments 3 and 6, whereas increases in tibia ash were observed in experiments 2 and 6 as the level of vitamin D3 in the maternal diet increased. Body weight gain and tibia ash increased and Ca rickets incidence decreased as the vitamin D3 level in chick diets increased. An evaluation of the study indicates that chicks hatched from eggs laid by hens fed 2,000 or 4,000 IU of D3/kg as the maximum level of vitamin D3 had the highest body weight gains, and chicks fed 3,200 IU had the highest body weight and tibia ash and the lowest TD and Ca rickets incidences.

An automatic monitoring of the hatching process based on the noise of the hatching chicks

In this manuscript, a new tool is presented for automatic monitoring of the hatching process of eggs without opening the incubator doors. The amount of energy in the noise produced by the hatchlings was registered by means of a microphone and a personal computer for signal treatment. Evidence is shown that it is possible to detect exactly when the first chicks are hatched, the mean hatching time, and the finish of hatch. The information generated by this tool can be used by the hatchery manager to make the decision to end the incubation at the right moment, resulting in a higher number of first quality chicks without the risk of a reduced hatchability due to too early termination of the incubation process. The presented research also shows evidence that there is already a circadian rhythm in the newborn hatchling even when no external stimulus is present.

Adenohypophysis regulates cell proliferation in the gonads of the developing chick embryo

The aim of the present study was to evaluate the effect of hypophysectomy on cell proliferation in the left ovary and the left testis of 8- to 14-day-old chick embryos. Hypophysectomy was performed by the partial decapitation technique. At 44-46 h of incubation, chick embryo heads were sectioned at the mesencephalic level and the prosencephalic region removed. Embryos were further incubated until 8-14 days of development. Cell division was evaluated by bromodeoxyuridine (BrdU) incorporation and by counting the total number of somatic and germ cells in the gonads. The ovary displayed an exponential increase in the number of somatic and germ cells and a higher rate of BrdU incorporation compared to the testis. BrdU incorporation was reduced in the ovary of hypophysectomized embryos at 9-14 days of incubation, while in the testis, the reduction was significant at 14 days of development. Changes in the total number of somatic and germ cells further suggest that the absence of hypophysis affects the growth of the ovary earlier than the growth of the testis. Reduction in the number of somatic and germ cells after hypophysectomy in the ovary was reversed by a hypophyseal graft on the chorioallantoic membrane. The adenohypophysis regulates, probably through gonadotropic hormones, proliferation of somatic and germ cells in the gonads during chick embryo development.

Pre- and postnatal conditioning induced thermotolerance on body weight, physiological responses and relative asymmetry of broilers originating from young and old breeder flocks

The present experiment was conducted to examine the effects of pre- and postnatal conditioning to induce thermotolerance in broilers hatching from eggs orginating from younger and older breeder flocks. From each flock, 500 eggs were randomly divided into 2 groups and incubated at standard (SIT) and high (HIT) temperatures. At hatch, chicks were allotted to 36 floor pens. At 5 d of age 3 pens per parent age per incubation temperature were heat conditioned (C) for 24 h. At 21 d of age, 3 pens per parent age per incubation temperature were kept under standard (S) rearing temperatures, whereas the remaining broilers (including C) were moved to a heated room (H). Thus, there were 3 groups from 21 to 49 d including S, H, and C+H. The results indicated that to incubate eggs from younger parents at HIT before conditioning at 5 d may reduce deleterious effects of heat stress on body weight at slaughter age. However, HIT temperature decreased slaughter weight of broilers from older parents regardless of rearing temperature. Although conditioning did not prevent increments in rectal temperatures of broilers after 1 wk of heat stress (28 d), adaptation occurred thereafter for broilers from younger parents but not for broilers from older parents. Incubation temperature had no effect on plasma glucose, creatine kinase, uric acid, or triiodotryronine (T3) levels at d 21. There were no differences at 22, 25, or 28 d for T3 concentrations between the H and C+H groups. Overall relative asymmetry was not influenced by treatments on d 49. The results suggest that although pre- and postnatal conditioning may help broilers cope with heat stress, age of parent plays a major role in the ability of broilers to thermoregulate. This is especially the case for broilers originating from younger parents.

Material Properties and Residual Stress in the Stage 12 Chick Heart During Cardiac Looping

During the morphogenetic process of cardiac looping, the initially straight cardiac tube bends and twists into a curved tube. The biophysical mechanisms that drive looping remain unknown, but the process clearly involves mechanical forces. Hence, it is important to determine mechanical properties of the early heart, which is a muscle-wrapped tube consisting primarily of a thin outer layer of myocardium surrounding a thick extracellular matrix compartment known as cardiac jelly. In this work, we used microindentation experiments and finite element modeling, combined with an inverse computational method, to determine constitutive relations for the myocardium and cardiac jelly at the outer curvature of stage 12 chick hearts. Material coefficients for exponential strain-energy density functions were found by fitting force-displacement and surface displacement data near the indenter. Residual stress in the myocardium also was estimated. These results should be useful for computational models of the looping heart.