Retinoic acid influences the timing and scaling of avian wing development.

A fundamental question in biology is how embryonic development is timed between different species. To address this problem, we compared wing development in the quail and the larger chick. We reveal that pattern formation is faster in the quail as determined by the earlier activation of 5'Hox genes, termination of developmental organizers (Shh and Fgf8), and the laying down of the skeleton (Sox9). Using interspecies tissue grafts, we show that developmental timing can be reset during a critical window of retinoic acid signaling. Accordingly, extending the duration of retinoic acid signaling switches developmental timing between the quail and the chick and the chick and the larger turkey. However, the incremental growth rate is comparable between all three species, suggesting that the pace of development primarily governs differences in the expansion of the skeletal pattern. The widespread distribution of retinoic acid could coordinate developmental timing throughout the embryo.

In vitro characterization and genetic diversity of Bordetella avium field strains.

Bordetella avium (BA) is a respiratory pathogen of particular importance for turkeys. Specific adherence and damage to the respiratory epithelia are crucial steps of the pathogenesis, but knowledge about the mechanisms and the variety of virulence in field strains is limited. We analysed 17 BA field strains regarding their in vitro virulence-associated properties in tracheal organ cultures (TOC) of turkey embryos, and their genetic diversity. The TOC adherence assay indicated that BA field strains differ considerably in their ability to adhere to the tracheal mucosa, while the TOC ciliostasis assay illustrated a high degree of diversity in ciliostatic effects. These two virulence-associated properties were associated with each other in the investigated strains. Three of the investigated strains displayed significantly (P > 0.05) lower in vitro virulence in comparison to other strains. Genetic diversity of BA strains was analysed by core genome multilocus sequence typing (cgMLST). We applied a cgMLST scheme comprising 2667 targets of the reference genome (77.3% of complete genome, BA strain 197N). The results showed a broad genetic diversity in BA field strains but did not demonstrate a correlation between sequence type and virulence-associated properties. The cgMLST analysis revealed that strains with less marked virulence-associated properties had a variety of mutations in the putative filamentous haemagglutinin gene. Likewise, amino acid sequence alignment indicated variations in the protein. The results from our study showed that both adherence and ciliostasis assay can be used for virulence characterization of BA. Variations in the filamentous haemagglutinin protein may be responsible for reduced virulence of BA field strains.

In ovo injection of branched-chain amino acids: Embryonic development, hatchability and hatching quality of turkey poults.

In this study, the influence of a branched-chain amino acid blend (BCAA composed of 3 l-leucine:1 l-valine:2 l-isoleucine) injected into the amniotic fluid was evaluated for embryonic growth, yolk-sac (YS) utilization and development of gastrointestinal tract (GIT) and skeletal muscles of turkey embryos from day 24 of incubation (24E) to hatching, together with hatchability, poult quality and liver L* (lightness), a* (redness) and b* (yellowness) values at hatch. At day 22 of incubation, embryonated eggs (n = 240) were assigned to three treatments, that is, eggs were not injected (control, NC) or injected with 1.5 ml sterile solution with 0.9% salt (SA) or 0.2% BCAA blend (BCAAb). These solutions were injected manually into the amniotic fluid of the embryonated eggs. To determine weights and lengths (where appropriate) of the studied organs and tissues, four embryonated eggs and poults per treatment were selected at 24E and at hatch. While the BCAAb decreased the YS and embryo weight, hatchability and the liver L* value, it increased the weight and quality of poults and the weights of breast and thigh muscles at hatch. In conclusion, the in ovo feeding of the BCAA blend negatively affected hatchability but positively affected hatching weight and poult quality by improving development of skeletal muscles and by regulating energy metabolism.

Observations of turkey eggs stored up to 27 days and incubated for 8 days: embryo developmental stage and weight differences and the differentiation of fertilized from unfertilized germinal discs.

For logistical reasons, egg storage prior to incubation is a growing practice in the commercial turkey industry. Yet the consequence of increasing egg storage over 7 d is a progressive increase in embryo mortality. The objective of this study was to provide the information necessary to differentiate an early dead embryo from an unfertilized egg after 8 days of incubation (DOI). Five groups of eggs each from inseminated and virgin hens were stored for progressively increasing periods of time (5-d or less, 6 to 10 d, 11 to 15 d, 16 to 20 d, and 21 to 27 d) and incubated. At 8 DOI, eggs were examined and the stage of development (Hamburger and Hamilton, 1951) and embryo weights in normally developed eggs were determined. There was a significant negative correlation between the stage of development and embryo weight with increasing storage periods. All remaining eggs from the inseminated and virgin hens were broken-out and the appearance of the yolk and the fertilized and unfertilized germinal discs examined. The yolks of both hen groups with unfertilized ova maintained a homogeneous uniform yellow-orange color. In contrast, yolks of ova that had been fertilized, with or without early-dead embryos, and yolks from virgin hens that showed evidence of parthenogenetic development (3%) had a heterogeneous appearance. Using fluorescence microscopy, the heterogeneous appearance was due to sheets of aberrant cells and less frequently dispersed cells and folds of the perivitelline layer. It was concluded that clear egg breakouts need to be performed to more accurately assess the impact of egg storage on embryonic mortality. Furthermore, such breakouts should be performed with a high intensity light directed across the surface of the germinal disc to clearly differentiate the subtle differences between an early-dead embryo and an unfertilized germinal disc.

Structure-Activity Relationships for DNA Damage by Alkenylbenzenes in Turkey Egg Fetal Liver.

Certain alkenylbenzenes (AB), flavoring chemicals naturally occurring in spices and herbs, are established to be cytotoxic and hepatocarcinogenic in rodents. The purpose of the present study was to determine the DNA damaging potential of key representatives of this class using the Turkey Egg Genotoxicity Assay. Medium white turkey eggs with 22- to 24-day-old fetuses received three injections of nine AB with different carcinogenic potentials: safrole (1, 2 mg/egg), methyl eugenol (2, 4 mg/egg), estragole (20, 40 mg/egg), myristicin (25, 50 mg/egg), elemicin (20, 50 mg/egg), anethole (5, 10 mg/egg), methyl isoeugenol (40, 80 mg/egg), eugenol (1, 2.5 mg/egg), and isoeugenol (1, 4 mg/egg). Three hours after the last injection, fetal livers were harvested for measurement of DNA strand breaks, using the comet assay and DNA adducts formation, using the nucleotide(3) (2)P-postlabeling assay. Estragole, myristicin, and elemicin induced DNA stand breaks. These compounds as well as safrole, methyl eugenol and anethole, at the highest doses tested, induced DNA adduct formation. Methyl isoeugenol, eugenol, and isoeugenol did not induce genotoxicity. The genotoxic AB all had the structural features of either a double bond in the alkenyl side chain at the terminal 2',3'-position, favorable to formation of proximate carcinogenic 1'-hydroxymetabolite or terminal epoxide, or the absence of a free phenolic hydroxyl group crucial for formation of a nontoxic glucuronide conjugate. In contrast, methyl isoeugenol, eugenol and isoeugenol, which were nongenotoxic, possessed chemical features, unfavorable to activation.

Expression of small intestinal nutrient transporters in embryonic and posthatch turkeys.

Nutrients are absorbed in the small intestine through a variety of transporter proteins, which have not been as well characterized in turkeys as in chickens. The objective of this study was to profile the mRNA expression of amino acid and monosaccharide transporters in the small intestine of male and female turkeys. Jejunum was collected during embryonic development (embryonic d 21 and 24, and d of hatch (DOH)) and duodenum, jejunum, and ileum were collected in a separate experiment during posthatch development (DOH, d 7, 14, 21, and 28). Real-time PCR was used to determine expression of aminopeptidase N (APN), one peptide (PepT1), 6 amino acid (ASCT1, b(o,+)AT, CAT1, EAAT3, LAT1, y(+)LAT2) and 3 monosaccharide (GLUT2, GLUT5, SGLT1) transporters. Data were analyzed by ANOVA using JMP Pro 11.0. APN, b(o,+)AT, PepT1, y(+)LAT2, GLUT5, and SGLT1 showed increased expression from embryonic d 21 and 24 to DOH. During posthatch, all genes except GLUT2 and SGLT1 were expressed greater in females than males. GLUT2 was expressed the same in males as females and SGLT1 was expressed greater in males than females. All basolateral membrane transporters were expressed greater during early development then decreased with age, while the brush border membrane transporters EAAT3, GLUT5, and SGLT1 showed increased expression later in development. Because turkeys showed high-level expression of the anionic amino acid transporter EAAT3, a direct comparison of tissue-specific expression of EAAT3 between chicken and turkey was conducted. The anionic amino acid transporter EAAT3 showed 6-fold greater expression in the ileum of turkeys at d 14 compared to chickens. This new knowledge can be used not only to better formulate turkey diets to accommodate increased glutamate transport, but also to optimize nutrition for both sexes.

Investigating Turkey Enteric Picornavirus and Its Association with Enteric Disease in Poults.

Previous research into the viral community in the poultry gastrointestinal tract has revealed a number of novel and partially described enteric viruses. It is evident that the poultry gut viral community remains minimally characterized and incompletely understood. Investigations into the microbiome of the poultry gut have provided some insight into the geographical distribution and the rapidly evolving taxonomy of the avian enteric picornaviruses. The present investigation was undertaken to produce a comparative metagenomic analysis of the gut virome from a healthy turkey flock versus a flock placed in the field. This investigation revealed a number of enteric picornavirus sequences that were present in the commercial birds in the field that were completely absent in the healthy flock. A novel molecular diagnostic assay was used to track the shedding of field strains of turkey enteric picornavirus in commercial poults inoculated with picornavirus-positive intestinal homogenates prepared from turkeys that were experiencing moderate enteric disease. The propagation of this novel enteric picornavirus in commercial poults resulted in significant reduction in weight gain, and suggests that this common inhabitant of the turkey gut may result in performance problems or enteric disease in the field.

Thermal manipulations of turkey embryos: The effect on thermoregulation and development during embryogenesis.

Previous studies conducted on meat-type chickens in our laboratory showed that thermal manipulations (TMS:) of the embryo during the time window of the hypothalamus-hypophysis-thyroid axis development and maturation significantly reduced the metabolic rates of the embryo and the chicken, improving the posthatch feed conversion rate (FCR:). The aim of the present study was to investigate the effect of intermittent TMs during turkey embryogenesis on embryo development. Fertile turkey eggs were divided into three treatments: control; 6H--with TM by elevation of temperature and RH by 1.7°C and 9%, respectively, above the control conditions for 6 h/d, from E10 through E22, i.e., 240 through 552 h of incubation; and 12H--with TM as above, for 12 h/d, during the same time period. From E0 through E10 and from E23 onward all eggs were incubated under control conditions. The embryo growth rate was not negatively affected by TM. During TM eggshell temperature, the embryonic heart rate and oxygen consumption were elevated by the manipulation while the embryos were in their ectothermic phase. However, by the end of the TM period and until hatch (the endothermic phase) these parameters were significantly lower in both TM treatments than in the control, indicating a lower metabolic rate and heat production. The TM embryos hatched approximately 10 h earlier than the controls, without any negative effects on chick body weight or hatchability. Nevertheless, TM treatments resulted in a higher proportion of chicks with unhealed navels. Body temperature at hatch was significantly lower in the TM chicks than in the controls, suggesting lower heat production and metabolic rate, which might affect the energy requirements for posthatch maintenance. It was concluded that TM during turkey embryogenesis might have altered the thermoregulatory set point, and thus lowered the embryo metabolic rate, which might have a long-lasting posthatch effect.

A case of bronze turkey twins developing from hatching.

A double-yolked egg that was laid by an 11-month-old bronze turkey hen on 2 April, 2013 was reported. The presented case of developing turkey twin embryos is the first ever described case for this species. The egg weighed 125 g and had 74.6 mm in length and 53.0 mm in width. The embryos died between the 23rd and 24th day of incubation. Both twin 1 and twin 2 were fully developed with body weights of: 37.7 g and 40.3 g, respectively. The likely causes of death include inappropriate arrangement of embryos and insufficient gas exchange in the last period of incubation. The embryos were arranged along the long axis of the egg, one underneath the other, and were closely adhering to one another. The twins were different in plumage pigmentation. In twin 1, a spontaneous mutation of plumage pigmentation (B) was observed, whereas twin 2 showed appropriate pigmentation (b+) in respect to parents.

The potential for archiving and reconstituting valuable strains of turkey (Meleagris gallopavo) using primordial germ cells.

Diseases such as avian influenza can destroy turkey flocks, potentially resulting in the loss of valuable or rare genetic material. Consequently, there is an urgent need to develop a means to archive such germplasm. Germline chimeras produced by intravascular transfer of primordial germ cells (PGC) have been reported in other avian species but not turkeys. This study examined the feasibility of both establishing an archive of frozen PGC, and producing germline chimeras by injecting the thawed PGC into host embryos. To meet these aims, the following experiments were performed: (1) PGC identification within turkey embryos; (2) development of an efficient method for isolation of turkey PGC; (3) demonstration that PGC can be cryopreserved, recovered, and retain viability; (4) reinjection into embryos and detection of injected PGC. Primordial germ cells were identified using periodic acid-Schiff reagent and the immunological marker OLP-1. Bloodstream PGC were isolated using Ficoll density gradient centrifugation with PGC recovery peaking at stages 13, 14, and 15 with 32 ± 4.9, 33 ± 6.4, and 26 ± 5.4 PGC recovered, respectively. Primordial germ cells were frozen using Dulbecco's modified Eagle medium, 20% fetal calf serum, and 10% dimethylsulfoxide and demonstrated 90 ± 1.7% viability after 3 mo frozen in liquid nitrogen. Freshly isolated and frozen thawed DiI- and Q-Tracker-labeled PGC repopulated stage 30 gonads after vascular transfer into ex ovo cultured embryos. The DiI-labeled cells repopulated gonads less frequently, with 36 ± 13.2% of gonads containing the DiI-labeled PGC, and 7 ± 3.8% of reinjected PGC reaching the gonads of positive embryos. The Q-tracker-labeled cells were detected more frequently in embryos, with 67 ± 21.1% having positive signals, and 44 ± 4.9% of reinjected Q-tracker-labeled PGC colonized the gonads of positive embryos. This study demonstrated the feasibility of using turkey PGC to archive turkey germplasm from different strains because frozen PGC reintroduced into host embryos can colonize the host gonads, suggesting the possibility of producing turkey germline chimeras.

Anisotropic growth shapes intestinal tissues during embryogenesis.

Embryogenesis offers a real laboratory for pattern formation, buckling, and postbuckling induced by growth of soft tissues. Each part of our body is structured in multiple adjacent layers: the skin, the brain, and the interior of organs. Each layer has a complex biological composition presenting different elasticity. Generated during fetal life, these layers will experience growth and remodeling in the early postfertilization stages. Here, we focus on a herringbone pattern occurring in fetal intestinal tissues. Common to many mammalians, this instability is a precursor of the villi, finger-like projections into the lumen. For avians (chicks' and turkeys' embryos), it has been shown that, a few days after fertilization, the mucosal epithelium of the duodenum is smooth, and then folds emerge, which present 2 d later a pronounced zigzag instability. Many debates and biological studies are devoted to this specific morphology, which regulates the cell renewal in the intestine. After reviewing experimental results about duodenum morphogenesis, we show that a model based on simplified hypothesis for the growth of the mesenchyme can explain buckling and postbuckling instabilities. Being completely analytical, it is based on biaxial compressive stresses due to differential growth between layers and it predicts quantitatively the morphological changes. The growth anisotropy increasing with time, the competition between folds and zigzags, is proved to occur as a secondary instability. The model is compared with available experimental data on chick's duodenum and can be applied to other intestinal tissues, the zigzag being a common and spectacular microstructural pattern of intestine embryogenesis.

Metabolic profiling of late-term turkey embryos by microarrays.

The last stages of embryonic development are crucial for turkeys as their metabolism shifts to accommodate posthatch survival and growth. To better understand the metabolic change that occurs during the perinatal period, focused microarray methodology was used to identify changes in the expression of key genes that control metabolism of turkey embryos from 20 d of incubation (E) until hatch (E28). Gene expression patterns were evaluated in liver, pectoral muscle, and hatching muscle and were associated with measured embryonic growth and tissue glycogen concentration. Within the studied period, the expression of 60 genes significantly changed in liver, 53 in pectoral muscle, and 51 in hatching muscle. Genes related to lipid metabolism (enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, 3-hydroxymethylglutaryl-CoA reductase, acetyl-CoA carboxylase, lipoprotein lipase, and thyroxine deiodinase) had reduced expression between E22 and E26, corresponding to the period of expected limited oxygen supply. In contrast, genes related to opposing pathways in carbohydrate metabolism, such as glycolysis and gluconeogenesis (hexokinases, glucose-6 phosphatase, phosphofructokinases, glucose 1-6 phosphatase, pyruvate kinase, and phosphoenolpyruvate carboxykinase), or glycogenesis and glycogenolysis (glycogen synthase and glycogen phosphorylase) had rather static expression patterns between E22 and E26, indicating their enzymatic activity must be under posttranscriptional control. Metabolic survey by microarray methodology brings new insights into avian embryonic development and physiology.

Effects of a higher incubation temperature between embryonic day 9 and 12 on growth and meat quality characteristics of turkeys.

1. The study investigated the influence of manipulating incubation temperature for a short period on the post-hatch development up to week 16 in male and female BUT Big 6 turkeys. 2. Eggs were incubated at a control temperature of 37·5°C and 55% RH until d 18 when transferred to a hatcher at 37·5°C and 85% RH. For a 4 d period between embryonic day 9 (ED 9) and 12, eggs were incubated at 38·5°C and 55% RH (HT). 3. Birds were slaughtered at 16 weeks of age to analyse meat quality parameters of the Musculus pectoralis superficialis (MPS). 4. Across both incubation treatments, the turkey males had significantly higher live and breast weights, but lower breast yields than the females. The sex of the animals only influenced the yellowness of the MPS with lower values in the males. 5. Temperature manipulation resulted in significantly decreased live weights of HT birds compared with the control animals across all ages in both sexes. No impact of incubation treatment on meat quality characteristics was found. 6. The results indicate a negative effect of higher incubation temperature on the post-hatch growth, possibly by influencing the mechanisms that regulate the hypertrophic growth of the muscle fibres.

The effects of genotype on embryonic development in eggs from divergent turkey genotypes.

Unique turkey genotypes and reciprocal crosses of these lines were used to study the relationship between egg size, posthatch growth potential, and selected aspects of embryonic development. A line of turkeys selected for increased egg production (E), its randombred control line (RBC1), a line selected for increased 16-wk BW (F line), and its randombred control line (RBC2) were the pure lines used in each of 2 experiments. In experiment 1, a sample of E-line hens were mated to either E line (E/E) or RBC1 toms (RBC1/E), and RBC1 hens were mated to RBC1 toms (RBC1/RBC1). Egg weight at set and at 25 d of incubation was significantly lower in the E/E and RBC1/E crosses compared with that of the RBC1/RBC1 eggs. On d 21 and 25 of incubation and at hatch, the yolk-free wet embryo weights of E/E and RBC1/E embryos were similar, and both weighed significantly less than the RBC1/RBC1 embryos (P ≤ 0.001). Similar observations were observed for the residual yolk sac weight at each of those developmental ages. In experiment 2, embryos from the F line, RBC2, RBC1, E, and 2 reciprocal crosses (RBC1/E, E/RBC1) were compared at various time points during the course of incubation. Egg weight was consistently highest in the F line and lowest in the E line and intermediate in the RBC1 and RBC2 lines. Egg weight followed the maternal genotype in the E/RBC1 and RBC1/E reciprocal crosses. On embryonic d 19, 23, and 26, the order of yolk-free weight embryo weights followed closely the pattern observed for egg weight. In summary, egg weight and embryonic development is largely controlled by the maternal genotype. This should be considered when making inference to posthatch selection effects on embryonic development.

The effect of dietary selenium source on embryonic development in Turkeys.

The objective of this study was to determine the effect of dietary selenium source on the growth and development of turkey embryos, and egg hatchability. White broad-breasted BUT Big 6 turkeys (1800 females and 150 males) were placed under optimum management conditions. Turkey diets were supplemented with organic selenium, and in the other with inorganic selenium, in the amount of 0.3 ppm. Eggs intended for incubation and examination were collected in week 2, 10, 18 and 23 of the laying season. The average egg weight was higher (p < or = 0.05) in laying hens fed a diet with organic selenium than in layers receiving inorganic selenium. The rate of yolk sac retraction was faster in embryos from the group fed a diet with inorganic selenium, and it reached 0.59 of the complete yolk sac on day 25 of incubation (p < or = 0.05). Selenium source had no effect on the hatching rates of fertilized eggs, which reached 79.61% and 79.84% in laying hens fed organic and inorganic selenium, respectively. In the flocks fed diets supplemented with organic selenium, dead embryos were more frequently characterized by problems with protein utilization (19.28%) and delayed pipping (10.83%). Embryo death rates at the first mortality peak were higher in layers fed inorganic selenium than in those receiving organic selenium (15% vs. 13.5%). The second embryo mortality peak occurred earlier (day 26) in laying hens fed inorganic selenium than in those fed organic selenium (day 28).

A rapid and simple assay for human blood malignancy engraftment, homing and chemotherapy treatment using fluorescent imaging of avian embryos.

Detection of grafted human cells in mice using fluorescence is a rapid and simple technique whose use is continually expanding. Robust engraftment of human hematological malignancy (HHM) lines and patient cells into the naturally immunodeficient turkey embryo has recently been demonstrated by polymerase chain reaction (PCR), fluorescence activated cell sorting (FACS) and histology. We demonstrate here that fluorescence imaging is a rapid and simple technique for detecting engraftment and homing of cells derived from HHM in turkey embryos. Raji lymphoma cells expressing a far-red fluorescent protein were injected intravascularly into turkey embryos and fluorescence was detected 8 days later in their limbs and skulls. Much stronger signals were obtained after removal of the bones from the limbs. Unlabeled Raji cells did not give a fluorescent signal. Treatment with doxorubicin dramatically reduced the fluorescent signal. Intravenously injected HL-60 leukemia cells labeled with infrared-fluorescing dye were detected in the bone marrow after 16 h. Homing was active, although some non-specific fluorescence was present. Use of fluorescence imaging of HHM in turkey embryos is therefore feasible and reduces the time, effort and expense for detecting engraftment. This technique has potential to become a high-throughput xenograft system for hematological chemotherapy development and testing, and for study of hematological cell homing.

Identification and characterization of a neutralizing-epitope-containing spike protein fragment in turkey coronavirus.

Little is known about the neutralizing epitopes in turkey coronavirus (TCoV). The spike (S) protein gene of TCoV was divided into 10 fragments to identify the antigenic region containing neutralizing epitopes. The expression and antigenicity of S fragments was confirmed by immunofluorescence antibody (IFA) assay using an anti-histidine monoclonal antibody or anti-TCoV serum. Polyclonal antibodies raised against expressed S1 (amino acid position 1 to 573 from start codon of S protein), 4F/4R (482-678), 6F/6R (830-1071), or Mod4F/Epi4R (476-520) S fragment recognized native S1 protein and TCoV in the intestines of TCoV-infected turkey embryos. Anti-TCoV serum reacted with recombinant 4F/4R, 6F/6R, and Mod4F/Epi4R in a western blot. The results of a virus neutralization assay indicated that the carboxyl terminal region of the S1 protein (Mod4F/Epi4R) or the combined carboxyl terminal S1 and amino terminal S2 protein (4F/4R) possesses the neutralizing epitopes, while the S2 fragment (6F/6R) contains antigenic epitopes but not neutralizing epitopes.

Transcriptional profiling identifies differentially expressed genes in developing turkey skeletal muscle.

BACKGROUND: Skeletal muscle growth and development from embryo to adult consists of a series of carefully regulated changes in gene expression. Understanding these developmental changes in agriculturally important species is essential to the production of high quality meat products. For example, consumer demand for lean, inexpensive meat products has driven the turkey industry to unprecedented production through intensive genetic selection. However, achievements of increased body weight and muscle mass have been countered by an increased incidence of myopathies and meat quality defects. In a previous study, we developed and validated a turkey skeletal muscle-specific microarray as a tool for functional genomics studies. The goals of the current study were to utilize this microarray to elucidate functional pathways of genes responsible for key events in turkey skeletal muscle development and to compare differences in gene expression between two genetic lines of turkeys. To achieve these goals, skeletal muscle samples were collected at three critical stages in muscle development: 18d embryo (hyperplasia), 1d post-hatch (shift from myoblast-mediated growth to satellite cell-modulated growth by hypertrophy), and 16 wk (market age) from two genetic lines: a randombred control line (RBC2) maintained without selection pressure, and a line (F) selected from the RBC2 line for increased 16 wk body weight. Array hybridizations were performed in two experiments: Experiment 1 directly compared the developmental stages within genetic line, while Experiment 2 directly compared the two lines within each developmental stage. RESULTS: A total of 3474 genes were differentially expressed (false discovery rate; FDR < 0.001) by overall effect of development, while 16 genes were differentially expressed (FDR < 0.10) by overall effect of genetic line. Ingenuity Pathways Analysis was used to group annotated genes into networks, functions, and canonical pathways. The expression of 28 genes involved in extracellular matrix regulation, cell death/apoptosis, and calcium signaling/muscle function, as well as genes with miscellaneous function was confirmed by qPCR. CONCLUSIONS: The current study identified gene pathways and uncovered novel genes important in turkey muscle growth and development. Future experiments will focus further on several of these candidate genes and the expression and mechanism of action of their protein products.

Ultrastructural development of the small intestinal mucosa in the embryo and turkey poult: A light and electron microscopy study.

The potential for growth and feed efficiency in turkey poults directly correlates with the early development of the intestinal epithelium. Although the metabolic aspects of enteric maturation have been studied, little is known about the ultrastructural development of the enteric epithelium in the turkey embryo and poult. Hence, the objective of this study was to document the morphological and ultrastructural development of the jejunum mucosa in turkeys, from 15 d of incubation (embryonic day; E) to 12 d posthatch. Intestinal samples from 4 embryos or poults were collected and analyzed by light and electron microscopy (transmission and scanning). In addition, amniotic fluid volume was determined in 6 eggs from E15 to E25. Longitudinal previllus ridges at E15 gradually formed zigzag patterns that led to the formation of 2 parallel lines of mature villi by E25. The volume of amniotic fluid was rapidly depleted as the embryo swallowed it between E19 and E25. During this period, a major increase occurs in villus height, the apical end of epithelial cells is gradually tightened by the junctional complex, and mature goblet cells are visible at the apical end of villi. Villus height steadily increases until reaching a plateau at 8 d. Villi morphology shifts gradually from finger-like projections before hatch to leaf-like projections by 12 d. At this age, the enteric epithelium is in intimate association with microbes such as segmented filamentous bacteria. The profound morphological adaptations of the turkey gut epithelium in response to amniotic fluid swallowing before hatch, and dietary factors and bacteria after hatch, demonstrate the plasticity of the enteric epithelium at this time. Hence, the supplementation of enteric modulators before hatch (in ovo feeding) and after hatch has the potential to shape gut maturation and enhance the growth performance of turkey poults.

Influence of parent flock age on embryonic metabolism in modern turkey strains.

The metabolic response of some galliform embryos to embryonic heat production (EHP) and how incubation conditions have been adjusted to prevent overheating of embryos is well established in broiler breeders. However, the daily metabolic status of turkey embryos has not been studied or established in turkey embryos. The objectives of the current research were therefore to determine the respiratory (eggshell conductance, G) and metabolic status (EHP) of 2 modern turkey genetic strains [Hybrid (H) and Nicholas (N)] and 4 parent flock ages [young (Y, 30 wk), peak (P, 34 wk), mature (M, 55 wk), and old (O, 60 wk)] during incubation. To measure G, moisture loss from 15 eggs/genetic strain per flock age and saturated vapor pressure measured between the eggshell and its immediate environment were used. Daily embryonic O(2) consumption and CO(2) production rates were assessed 6 times each day from embryos of eggs (n = 11 eggs/genetic strain per flock age) incubated in individual metabolic chambers and were used to determined daily EHP. Data were analyzed using the mixed model procedure of SAS at P ≤ 0.05. The results showed that the G values (g/d per mmHg) were significantly different for the interaction between genetic strain and parent flock age (H × Y = 17.71, H × P = 17.53, H × M = 19.73, H × O = 26.46, N × Y = 16.70, N × P = 20.96; N × M = 25.47, N × O = 26.05; P = 0.0227). Daily EHP (mW) was higher in embryos from the O flock than in embryos from the Y flock during all days presented except at 8, 25, and 28 d of incubation (4 d: Y = 1.00, P = 0.93, M = 1.60, O = 1.75; 12 d: Y = 19.0, P = 20.0, M = 21.6, O = 23.4; 16 d: Y = 51.7, P = 60.5, M = 65.9, O = 70.8; 20 d: Y = 129, P = 146, M = 144, O = 155; 24 d: Y = 154, P = 188, M = 167, O = 180; 26 d: Y = 169, P = 199, M = 197, O = 230; and 27 d: Y = 231, P = 265, M = 288, O = 307; P < 0.05). The data showed that metabolic differences existed between embryos from flocks of different ages and that embryos from older flocks were metabolizing at a higher rate and could be subject to overheating, which requires further investigation. On the basis of the data, turkey eggs from flocks of different ages should be incubated separately for optimal physiological performance.