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PubMed1977

Shell thinning and reproductive impairment in black ducks after cessation of DDE dosage.

Captive black ducks (anas rubripes) were fed dietary DDE [1,1-dichloro-2,2-bis (p-chlorophenyl)ethylene] at 10 ppm (dry weight; about 2 ppm on a natural diet basis) for 2 breeding seasons, then untreated feed for 2 succeeding years. Residues of DDE in the carcasses of adults declined 90% during the 2-year clean-up period. Following 2 years of dietary DDE, mean residues in eggs reached 64.9 ppm. Even after 2 years on clean feed, DDE residues in the eggs averaged 6.2 ppm or 9.5% of the mean DDE level reached after 2 years on treated feed. Shells of eggs from treated hens were about 20% thinner than shells of eggs from controls. Stoppage of DDE dosage resulted in progressively thicker shells, yet even after 2 years on untreated feed hens laid eggs with shells about 10% thinner than control hens. After DDE was removed from the diet, DDE residues in the eggs decreased, shell thickness increased, and reproductive success improved. Hens previously exposed to DDE, but then fed clean feed for 2 years, still produced significantly fewer surviving ducklings than did control hens.

Animals↗

PubMed1986

Effects of suppression and resumption of shell formation and parathyroid hormone on uterine calcium-binding protein, carbonic anhydrase activity, and intestinal calcium absorption in hens.

The calcium absorption and duodenal and uterine vitamin D-dependent calcium-binding protein (CaBP-28K) levels were decreased in hens when eggshell calcification was suppressed by premature expulsion of the egg. Nevertheless, these levels remained higher than those of immature pullets or pullets treated with estrogen. The resumption of shell formation by hens which had previously laid soft-shell eggs was associated during calcification of the first egg with increases in intestinal Ca absorption. CaBP concentration, and alkaline phosphatase activity. The increase in uterine CaBP concentration preceded the stage of rapid calcium deposition. Uterine carbonic anhydrase activity was increased by sexual maturity but not consistently by shell formation. Ablation of the parathyroids just before the resumption of shell formation suppressed the increases in duodenal calcium absorption and CaBP concentration elicited by egg calcification. In contrast, the increase in CaBP level was maintained in the uterus of parathyroidectomized hens, in spite of the decreased shell deposition. Previous studies indicated that increased uterine CaBP associated with eggshell calcification is not elicited by vitamin D. The present study confirms this observation and also shows that these changes are not elicited by either PTH or sex steroid hormones.

Animals↗

PubMed1988

Levels of calcium and soluble collagen in turkey egg shell membranes.

1. This experiment examined the effect of weeks in egg production and type of housing confinement of turkey hens on calcium and soluble collagen levels in egg shell membranes; and discussion was given to their apparent relationship to gas exchange in turkey eggs. 2. The high level of acid-soluble collagen in inner and outer egg shell membranes of aging caged hens compared with the same aged floor-penned hens may have a relationship with the low hatchability generally recognized in caged hens. 3. The levels of calcium found in the outer shell membrane are low and appeared to decrease with the age of the hen. 4. There were no differences over time in levels of total collagen and neutral salt-soluble collagen (newly formed collagen) found in egg shell membranes of turkey hens confined in cages or floor pens. 5. It is suggested that the acid-soluble collagen levels found in inner shell membranes may have a relationship in limiting respiratory gas exchange during latter incubation time, and thus limit embryo survival.

Acids↗

PubMed2004

Changes in expression of AVT and AVT receptor (VT1) gene in hypothalamus and shell gland in relation to egg laying in white leghorn hen.

Oviposition is a complex phenomenon involving various regulatory mechanisms at the neuroendocrine levels. Present study was designed to access the changes in arginine vasotocin (AVT) and its receptor (VT1) gene expression in relation to the time of egg laying of white leghorn hen. The expression of AVT gene (Northern blot analysis and in situ hybridization) in the hypothalamus and localization of ir-AVT in the magnocellular neurons of paraventricular nuclei was studied 2 h before (-2 h), immediately after (0 h) and 2 h after (+2 h) egg laying. Simultaneous changes in the AVT and VT1 receptor gene in the shell gland, which finally responds to AVT for smooth muscle contraction and expulsion of egg, were also determined by semi-quantitative reverse transcriptase-polymerase chain reaction. The findings indicated increased hypothalamic AVT gene expression immediately after egg laying (0 h) when compared to 2 h before and 2 h after egg laying. AVT receptor gene expression in the shell gland also followed the same pattern. However, AVT gene expression in the shell gland, unlike that of hypothalamus was higher at -2 h compared to 0 and +2 h of oviposition. While highly significant increase was noted in plasma AVT concentration at the time of egg laying, other parameters such as plasma osmolality and ionic concentration (Na(+), K(+), Ca(2+), and Cl(-)) did not show any change. It is suggested that in addition to increased hypothalamic AVT transcript and peripheral release, local synthesis of AVT in the shell gland (paracrine release) may contribute to the contraction of shell gland smooth muscles during egg laying. Moreover, these findings clearly indicate temporal correlation of AVT and its receptor gene expression in different tissues during oviposition.

Animals↗

PubMed1999

The opercular bond in the egg-shell of the monogenean Entobdella soleae, a platyhelminth skin parasite of the common sole (Solea solea).

The monogenean (platyhelminth) skin parasite Entobdella soleae from the common sole (Solea solea) lays tetrahedral eggs. One of the 4 corners of the tetrahedron is a detachable operculum which is bonded to the rest of the egg-shell by cement. Most of this cement layer, beginning at the inner surface of the shell and running through almost to the outer surface (a distance of about 2 microns), is more or less uniform in thickness (30-38 nm), or tapers slightly. About 345 nm from the outer surface the cement layer narrows abruptly to about 10 nm. The cement is exposed on the inner surface of the shell, but in most eggs a layer of shell about 10 nm thick covers the narrow outer region of the cement layer. When experimentally perforated eggs were incubated with trypsin, the wide inner layer of cement was digested, but the narrow outer region initially remained intact. These observations are discussed in relation to the following (1) survival of the eggs during embryonic development, (2) hatching, (3) the 'hinge' often connecting the operculum to the empty egg-shell, (4) the rapid hatching that occurs in some other monogeneans.

Animals↗

PubMed1977

Studies on the avian shell gland during egg formation: aqueous and electrolytic composition of the mucosa.

The intracellular composition of the avian shell gland mucosa was studied at six stages of egg formation. 2. Total water content of the mucosa before shell calcification was 4-8 kg/kg dry weight (dw) and rose to 6-6 kg/kg dw during shell formation; 60% of the increase was intracellular and 40% extracellular. 3. The potassium concentration of the mucosa remained constant during egg formation. 4. Chloride was removed constantly from the mucosal cells during egg formation. 5. A model was constructed for the glandular cells which depicts them as primarily NaHCO3-secreting cells towards the luminal side and HCl-secreting cells towards the serosal side, their main function being to provide CO2/3- for shell formation. In this model, the columnar mucosal cells are responsible for the calcium used in shell formation.

Animals↗

PubMed1989

Regulation of net intestinal calcium uptake in hens laying obligatory soft-shelled eggs.

1. Individually caged laying hens had a loop of thread inserted into the shell gland. This resulted in the laying of soft shelled eggs. 2. A balance study was performed for a one week period before and after the operation. After the operation birds with threads consumed less calcium than before. Their requirements for calcium for eggshells decreased, resulting in increases in both calcium excreted and calcium retained. 3. Net calcium extraction in the digestive tract was measured in groups of birds with threads and intact controls, when shelling or not, by examining ratios of Ca to TiO2 in different gut segments. Observations were made during the period following premature oviposition in birds with threads, but within the normal shelling period of control birds. The period of study was at least two weeks after the operation. 4. Birds with threads absorbed less calcium than control birds up to the upper jejunum. 5. Control birds secreted calcium between the upper jejunum and colon, but birds with threads showed little change in absorption in this part of the digestive tract. 6. The increase in calcium absorption in intact birds was a response to the stimulus of shelling an egg or replacing calcium in medullary bone during a pause day, rather than of ovulation.

Animals↗

PubMed1999

Effects of drilling holes into the air cell of incubated goose eggs on distribution of oxygen partial pressures under the shell.

The purpose of this work was to measure changes in oxygen pressure in the air cell and under the eggshell (P(A)O2) of pre-pipping goose eggs before and after drilling holes into the air cell. Drilling a 0.6 mm (diameter of 0.9 mm) hole into the air cell caused an increase in air cell P(A)O2 of about 10 Torr. The rate of increase attenuated as hole area increased and reached about 21 Torr when the drilled area was 8.5 mm2. The P(A)O2 of intact eggs was not equally distributed under the shell. It was high in the air cell area (108 Torr) and decreased towards the pointed end (86 Torr). The increase in P(A)O2 after drilling a 4.9 mm2 hole was high in the air cell (18 Torr) and decreased with distance, becoming non-significant at the pointed end. The significant increase in P(A)O2 after drilling was limited to a distance of up to 38 mm along the shell from the edge of the air cell. This indicates that lateral diffusion in the shell membranes under the shell is limited. Drilling a hole of 3.5 to 4.9 mm2 was enough to increase air cell P(A)O2 in most of the eggs above the critical value of 100 Torr for hatching success. The increase in P(A)O2 was limited to about half the area of the shell and the average increase in P(A)O2 was 6.3 Torr (equivalent to a 0.9% increase in ambient O2). However, the blood perfusing chorioallantoic areas further away from the air cell edge may not be fully saturated with O2 and may not be sufficient to compensate fully for the low O2 availability caused by low eggshell conductance.

Animals↗

PubMed2000

Gas exchange into shell eggs from cryogenic cooling.

The gas composition of the air cell in a shell egg is influenced by heating from egg washing and candling and the method of cooling and storage. This study found that N2 gas (-122 C), CO2 gas (-45 C), and cold air (-15 C) could be used to rapidly cool shell eggs from 47.7 C to 7 C in 30 min or less. These results suggest that the gas composition of the air cell in shell eggs can be significantly modified using N2 cooling and CO2 cooling. Commercial field studies have shown that these modifications, which take place during cryogenic cooling, can significantly reduce microbial levels and increase shelf life of shell eggs. Storage in a modified atmosphere environment further enhanced these changes. It was found that the CO2 concentration in the air cell of a shell egg can be increased from 0.04 to 48% by CO2 cooling and storage in a CO2 environment.

Animals↗

PubMed2002

Microbial contamination in inoculated shell eggs: I. Effects of layer strain and hen age.

Three Ottawa control strains and a current commercial laying stock were reared and housed under identical environmental and management conditions. Eggs were collected from each strain when hens were 32, 45, 58, 71, and 84 wk of age. The eggs were inoculated with Salmonella enteritidis (SE), Pseudomonasfluorescens (PF), or a combination of the two. After storage at 26 C, bacterial counts were obtained from the exterior shell surfaces (rinse), air cell, egg contents, and shell structure. SE and PF survived at different rates on the shell surface with as much as a 1 log difference during a given collection period. Egg content counts tended to be higher than eggshell counts in PF, whereas the opposite was true for SE. These data suggest that PF is a primary invader of eggs that is more capable of contaminating egg contents through the shell membranes than SE. The PF and SE data suggest that bacterial contamination of air cells, shells, and egg contents is more easily achieved in eggs from older hens than from younger hens. There were also differences between the strains. Control Strain 10 consistently maintained a lower level of contamination for both organisms in each sampling location. The overall results of this study suggest that genetic selection has altered the ability of eggs to resist microbial contamination and that screening for microbial integrity should be considered in the selection process among the laying egg breeders.

Age Factors↗

PubMed2003

Chemical composition of chicken eggshell and shell membranes.

This study was undertaken to determine the occurrence of uronic acid in chicken eggshell membranes and to compare chemical compositions among the inner and outer eggshell membranes and the organic matter of eggshell. We report here for the first time the occurrence of uronic acid in chicken eggshell membranes. Uronic acid concentrations were similar (P > 0.05) between the inner shell membrane and outer shell membrane but approximately fivefold higher (P < 0.05) in the organic matter of eggshell. Sialic acid concentrations were the highest (P < 0.05) in the organic matter of eggshell and higher (P < 0.05) in the inner than in the outer shell membrane. Nitrogen concentrations were the lowest (P < 0.05) in the organic matter of eggshell but relatively constant between the two shell membranes. Amino acid analysis showed that the contents of glycine and alanine were higher (P < 0.05) and those of proline and hydroxyproline were lower (P < 0.05) in the organic matter of eggshell compared to shell membranes.

Alanine↗

PubMedDate not supplied

Computed tomographic evaluation of dinosaur egg shell integrity.

The purpose of this study was to determine whether computed tomography (CT) could be used to identify hatching holes in partially embedded dinosaur eggs. One Faveololithus and two Dendroolithus eggs were examined using a fourth generation CT scanner. The eggs were partially embedded in a fossilized sediment matrix, with the exposed portion of the shell appearing intact. In CT images of all three eggs, the shells appeared hyperdense relative to the matrix. Hatching holes were visible as large gaps in the embedded portion of the shell, with inwardly displaced shell fragments. It was concluded that CT is an effective technique for nondestructively assessing dinosaur egg shell integrity.

Animals↗

PubMed2004

Embryonic exposure to oestrogen causes eggshell thinning and altered shell gland carbonic anhydrase expression in the domestic hen.

Eggshell thinning among wild birds has been an environmental concern for almost half a century. Although the mechanisms for contaminant-induced eggshell thinning are not fully understood, it is generally conceived to originate from exposure of the laying adult female. Here we show that eggshell thinning in the domestic hen is induced by embryonic exposure to the synthetic oestrogen ethynyloestradiol. Previously we reported that exposure of quail embryos to ethynyloestradiol caused histological changes and disrupted localization of carbonic anhydrase in the shell gland in the adult birds, implying a functional disturbance in the shell gland. The objective of this study was to examine whether in ovo exposure to ethynyloestradiol can affect eggshell formation and quality in the domestic hen. When examined at 32 weeks of age, hens exposed to ethynyloestradiol in ovo (20 ng/g egg) produced eggs with thinner eggshells and reduced strength (measured as resistance to deformation) compared with the controls. These changes remained 14 weeks later, confirming a persistent lesion. Ethynyloestradiol also caused a decrease in the number of shell gland capillaries and in the frequency of shell gland capillaries with carbonic anhydrase activity. These data suggested that a disrupted carbonic anhydrase expression was involved in the mechanism for the oestrogen-induced eggshell thinning found in this study. The results support our hypothesis that eggshell thinning in avian wildlife can result from a structural and functional malformation in the shell gland, induced by xeno-oestrogen exposure during embryonic development.

Animals↗

PubMed1984

Toxic shock-like syndrome in hens and its relationship to shell-less eggs.

Foreign materials were inserted into the hens' uteri and anti-inflammatory and immune suppressant drugs were used to determine possible causes of shell-less eggs. The presence of foreign shell-membranes and tampons in the uteri (shell glands) of hens caused a toxic shock-like syndrome ( TSLS ). Primary clinical signs were high fever, vomiting, diarrhea, and death. The presence of other materials, including inflated rubber balloons, had no adverse affect on the hens. Calcium carbonate deposits occurred on the surface of the balloons but not on other material inserted into the uteri. Injection of anti-inflammatory or immunosuppressive drugs did not increase shell weight in hens laying shell-less eggs. The hens' reproductive system was found to be sensitive in varying degrees to different types of foreign materials; thus, the avian female might serve as an animal model for studying toxic shock syndrome.

Animals↗

PubMed1986

The effect of variation of calcium intake on production performance and shell quality.

Two experiments were conducted to determine the effects of moderate variation of calcium intake on production performance and shell quality. In Experiment 1, birds were fed diets containing 1.5 and 5.5% calcium, respectively, in the first and second 3-day period of 10 6-day cycles. In Experiment 2, calcium concentrations alternated between 2 and 5%. In both experiments, control groups were fed a diet containing 3.5% calcium for the duration of the experiment (60 days). Birds were 28 weeks old at the beginning of Experiment 1 and 50 weeks old at the beginning of Experiment 2. Overall egg production, egg weight, egg mass, feed consumption, feed conversion, and body weight gain were consistently lower for the birds of the alternating groups than the birds of the control groups in both experiments. Shell quality as measured by shell thickness, breaking strength, specific gravity, and percent shell in most cases was significantly reduced within 24 hr of feeding the low calcium diets and improved to normal within 24 hr of feeding the high calcium diets in both experiments. These experiments suggest that calcium variation of the extent used in these experiments reduces optimum performance; shell quality is reduced within 24 hr of feeding a low calcium diet.

Animals↗

PubMed1988

Relationship of time of feeding and strain to egg shell quality and hatchability in broiler breeders.

The relationship of feeding time to egg production, egg weight, egg shell quality, fertility, and hatchability was examined in two trials. Slow and fast-feathering strain Hubbard females were used in Trial 1 and slow-feathering strain Arbor Acres females were used in Trial 2. Feeding times of 0800 or 1300 h throughout the laying periods were compared. Slow feathering females in Trial 1 exhibited significantly increased egg weight and significantly decreased percentage shell when compared with fast-feathering females. Feeding at 1300 h increased significantly egg specific gravity, egg shell weight, and percentage shell in Trials 1 and 2. Significant interactions of feeding time and strain occurred in Trial 1 with respect to fertility and hatch of all eggs set. Feeding at 1300 h increased fertility and hatch of all eggs set in fast-feathering hens but the opposite occurred in slow-feathering hens in Trials 1 and 2. Within slow-feathering hens, hatch of fertile eggs was decreased by 1.7% (Trial 1) and 1.5% (Trial 2). The results show that afternoon feeding that provides calcium intake near the time of egg shell calcification decreased significantly hatchability in eggs from two slow-feathering strains of females but not in eggs from a fast-feathering strain. These results suggest that altering time of feed intake can decrease hatchability.

Animals↗

PubMed1994

Effect of removing trace minerals from the diet of hens laying eggs with heavy or light shell weight.

Hy-Line W36 hens, 48-wk-old, were used to study the effect of removing either supplemental Fe, Cu, Zn, Mn, or all of them from the diet of hens laying eggs with heavy shell weight (HSW) or light shell weight (LSW). The experiment was conducted for 10 wk. Egg production (EP), egg mass (EM), feed consumption (FC), feed conversion efficiency (FE, grams feed:gram egg), egg weight (EW), shell weight (SW), percentage shell (PS), specific gravity (SG), percentage fertility, percentage hatchability of fertile eggs (HF), and percentage hatchability of total eggs set (HT) were measured. Removing trace minerals from the diet had no significant effect on EP, EM, FC, FE, EW, PS, SG, HF, or HT with either HSW or LSW hens. However, removing Mn from the diet significantly reduced SW with HSW hens. Diet by shell classes (HSW and LSW) interaction was not significant for any variable measured. The HSW hens had significantly higher EW, SW, PS, SG, and EM and lower EP, HF, and HT. However, there were no significant differences on FC or percentage fertility between the two groups of hens.

Animal Feed↗

PubMed1994

Egg shell penetration tendency of different Salmonella serotypes by attached ring color method.

To investigate the extent of Salmonella penetration through the egg shell, 200 eggs were dipped in red (for 3 minutes) and then in green (for 6 minutes) aqueous bland food color solution for the detection of positive penetration test areas. Each egg with positive penetration area, 5 spots of 1 cm in diameter, was marked for the attachment of steel cylinders (1 cm in diameter and height). These cylinders were filled with the test strain of Salmonella. Among 19 serotypes S. pullorum and S. gallinarum were nonmotile while the other 17 were motile. Among a total of 180 eggs (900 points) maximum (30%) penetration was in area III, where salmonellae invaded through cuticle, shell, inner and outer shell membranes, followed by area II (14.77%) and area I (4.6%). It was very well evident that penetration of salmonellae to the contents of eggs was maximum, while in area II the penetration was to outer shell membrane and in the least cases through the cuticle and shell. Penetration in area I is not significant and to some extent in area II as well, while invasion in area III is highly significant.

Animals↗