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PubMed1979

Oogenesis and egg-shell formation in Aspiculuris tetraptera Schulz (Nematoda: Oxyuroidea).

The ovary of Aspiculuris tetraptera has a prominent terminal cap cell. This is considered to be part of the ovarian epithelium. Oogonia detach from the short rachis and increase in size from 6 to 60 microns; accumulating hyaline granules, shell granules and glycogen. The hyaline granules persist in the eff cytoplasm after shell formation has been completed and are considered to be lipoprotein yolk. The shell granules contribute to the non-chitin fraction of the chitinous layer. A classification of the cytoplasmic inclusions of the nematode oocyte is proposed. Upon fertilization a vitelline membrane is formed which constitutes the vitelline layer of the egg-shell. The chitinous layer is secreted in the perivitelline space, between the vitelline layer and the egg oolemma. Upon completion of chitinous layer synthesis, the egg cytoplasm contracts away from its inner surface. The material of the lipid layer is secreted at the surface of the egg cytoplasm and adheres to the inner surface of the chitinous layer. During secretion of the chitinous and lipid layers by the egg cytoplasm, the uterine cells secrete the unit membrane-like external uterine layer and the crystalline internal uterine layer. A complex system of interconnecting spaces develops in the internal uterine layer. This system is open to the exterior via breaks in the external uterine layer. There is no direct involvement of the uterine cells in the formation of this structure.

Animals↗

PubMed1975

Influence of hormonal extracts on hens producing eggs with non-calcified or partially calcified shells and factors associated with this condition.

1. Daily injection of hypothalameal extract (HE) and adenohypophyseal extract (AE) into hens aged 56 or 67 weeks for 14 d did not significantly influence the production of shell-less (SL) or ultra-thin-shell (UTS) eggs. 2. The injection of HE significantly increased hard-shell (HS) egg production in the younger hens. 3. Neither AE nor HE affected egg weight, serum calcium, gain in body weight or food consumption. 4. In a third experiment hens selected for poor egg production laid at a rate of 58% of which 36% were SL, 29% UTS and 35% HS eggs. Whereas the production rate of the good layers was 65% of which 1-4% were SL and 1-4% were UTS eggs. 5. Specific gravity of HS eggs, serum calcium, weight of ovary, oviduct, or adenohypophysis did not differ between good and poor layers. 6. Since SL and UTS eggs are easily overlooked the decrease in egg production with age may be as great as indicated by normal production records; the problem may be concerned more with the mechanism of shell formation.

Animals↗

PubMed1987

Effect on shell strength of feeding supplemental sources of calcium to adult laying hens given insoluble grit during the rearing period.

1. An experiment was conducted to determine the separate and combined effects of giving insoluble grit during the rearing period and small or large particle size (0.3 mm and 3 to 8 mm in diameter) limestone or oyster shell, as extra sources of calcium, during the laying period. 2. For the entire laying period the extra sources of calcium resulted in improved shell strength but, overall, grit-supplements during the rearing period did not affect either egg shell strength or other performance traits. 3. An analysis for interactions however revealed that limestone of larger particle size coupled with rearing period-grit resulted in improved egg-shell strength during the last quarter of the laying period.

Animal Feed↗

PubMed1989

Egg shell quality responses of pullets given saline drinking water at different ages.

1. Saline drinking water given to pullets before sexual maturity had no effect on their subsequent egg shell quality. 2. Hens receiving saline drinking water from or after laying their first egg produced significantly more egg shell defects than hens receiving town water. 3. The production of eggs with defective shells occurred more rapidly when saline drinking water was given to 40-week-old hens than to hens during the first few weeks of lay. 4. The high incidence of egg shell defects resulting from the use of saline drinking water was reduced to control levels when hens in early lay were given town water for 5 weeks. This response was not observed with 40-week-old hens.

Age Factors↗

PubMed1990

Effect of 1 alpha,25-dihydroxycholecalciferol on egg shell quality and egg production.

1. The effect of replacing dietary cholecalciferol (D3) by 1 alpha,25-dihydroxycholecalciferol (1,25-(OH)2D3) on egg shell quality and egg production was tested on 32-week-old White Leghorn laying hens over 9 weeks. 2. Hens fed on a diet supplemented with 5 micrograms 1,25-(OH)2D3/kg diet, tended to lay more eggs, and the eggs had significantly higher specific gravity and percentage shell than eggs from control hens fed on a diet supplemented with 27.5 micrograms D3/kg diet. 3. The effect became apparent after about 4 weeks of treatment and persisted until the end of the test. 4. Hens fed on a diet without D3 supplement started to lay very thin or soft shelled eggs within 4 weeks, suggesting that the birds' reserves of D3 or its metabolites were depleted within this period. 5. The results suggest that 1,25-(OH)2D3 can be substituted for D3 in layer diets to improve egg shell quality.

Animals↗

PubMed1994

Relationship of plasma calcium and phosphorus to the shell quality of laying hens receiving saline drinking water.

1. From 36 to 43 weeks of age 210 White Leghorn laying hens were used to study the relationship of plasma calcium and phosphorus concentrations to egg-shell quality when saline drinking water was given. 2. Seven experimental treatments in which different amounts of sodium chloride were supplied by the food and/or the drinking water were compared. 3. Increasing salt intake through the drinking water or the food reduced shell thickness and shell calcium, and increased the numbers of damaged eggs. Sodium chloride given in the drinking water was more effective in reducing shell quality and increasing plasma calcium and phosphorus than sodium chloride given in the food.

Animals↗

PubMedDate not supplied

[Dynamics of amino acid and protein metabolism of laying hens after the administration of 15N-labeled wheat protein. 3. Incorporation of 15N into egg shell, egg white and egg yolk].

12 colostomized laying hybrids received a ration meeting their requirement of 15N labelled wheat with a 15N excess (15N') of 14.37 atom-% over 4 days. The 15N' of the total ration amounted to 4.47 atom-%. Each hen consumed 135 mg 15N' per day. On another 4 days the same rations with non labelled wheat were fed. The 12 hens laid 56 eggs during the 8 days of the experiment. They were divided into egg shell, white and yolk of egg. In addition, the protein of the white and yolk of egg was precipitated with trichloric acetic acid (TCA) and the nitrogen in these fractions was determined. On average of the 56 eggs, the N quota in the egg shell was 5.3%, in the white of egg 49.1% and in the yolk 45.6%. The atom-% 15N' in the shells of the eggs laid on the first day of the experiment was on average 0.21, whereas only 0.03 and 0.02 atom-% 15N' resp. could be detected in the white and yolks of the eggs. On the first day after the last 15N application the atom-% 15N' in the egg shell and the white of egg was highest and amounted to 2.33 and 2.43 atom-% resp. The highest value of 1.83 atom-% 15N' in the yolk was ascertained 3 days after the last 15N intake. The mean quota of TCA-precipitable N in the white of egg is 97.6% and in the yolk 94.4% of the respective total N. The atom-% 15N' in the non-protein N-compounds was higher than in the protein fractions.

Amino Acids↗

PubMed1992

[Effect of the manganese content in laying hen feed with different Ca and mineral levels on the egg shell quality and bone mineralization of hens].

Four experiments with 270, 44, 432 and 66800 Leghorn hens were carried out to investigate the influence of various Mn additions to diets differed in mineral or Ca contents on egg shell quality. The addition of 300 mg Mn/kg diet improved significantly egg shell breaking strength by 4 N over one year. The supply of 50-500 mg Mn/kg diet for 10-24 weeks of the second half of laying year did not influence the egg shell quality. Addition of mineral mixture or Ca grit to layer rations with adequate or higher Mn levels did not influence egg shell strength. High mineral content in a low manganese diet increased number of cracks by 3%. Strength, weight and ash content of tibia were significantly reduced by feeding a low mineral level. Addition of 50-150 mg Mn per kg low mineral diet normalized partially tibia stability in young hens. It was concluded that supplied dietary Manganese influences calcification positively only in young hens. High levels of Ca did not influence the effects of Mn. 50 mg Mn per kg layers mixture have been considered as an essential supply.

Animal Feed↗

PubMed2002

Changes in shell membranes during the development of quail embryos.

The shell membrane of an avian egg acts as a bag enclosing albumen and water. At its interface with the albumen, a smooth layer of homogeneous, dense material called the limiting membrane demarcates the shell membrane. The present study aimed to investigate changes in the limiting membrane during development of quail embryos that were grown with or without being turned. Sixty-three percent of the embryos were hatched after the eggs were incubated at 39 C and in 60% humidity with automatic rotation around their long axis and with their equatorial side down, whereas the hatch rate decreased to 24% when the eggs were incubated without being turned. The width of the limiting membrane at the equatorial region of turned eggs gradually decreased from 74 nm on Days 0 to 2 of incubation to 35 nm on Day 10 and thereafter. Conversely, water permeability, measured by evaporation through the shell membrane increased from 4 to 5 nL/mm2 per min on Days 0 to 6, to 9 nL/mm2 per min on Day 12 and thereafter. In stationary eggs, the decrease in the width of the limiting membrane on the lower side of eggs was delayed until Day 8 of incubation. The water permeability of the shell membrane in this group was 51% of that of the membrane on the upper side of eggs on Day 8 of incubation. Forty to forty-four nanometers seemed to be the critical width of the limiting membrane at which high water permeation could occur. It was also shown that the albumen hinders water permeation through the membrane. These results show that (1) the limiting membrane is made thin during the development over the whole surface with egg-turning, possibly through digestion of still unknown agents, and (2) this thinning accelerates the rate of water permeation through the membrane.

Animals↗

PubMed2007

Expression of positional candidates for shell thickness in the chicken.

Expression of 12 positional candidates for QTL affecting shell thickness at 53 wk of lay age (ST53) was investigated by real-time PCR in the distal part of chicken oviducts (uterus) with a forming eggshell. In the local chicken breed Green-legged Partridgenous, the complete cDNA CR523443 (ChEST985k21) was downregulated with ratio of means 0.49 (P < or = 0.01) in the group with low ST53 (248.6 +/- 16.62 microm) relative to the group with the highest ST53 (372.4 +/- 2.07 microm). Expression of this gene was highly correlated (0.85, P < or = 0.01) with shell thickness. No significant difference in expression between the 2 groups with thick (378.4 +/- 3.65 microm) and thin (227.8 +/- 8.99 microm) shell and no significant correlation of expression level with ST53 were detected in Rhode Island Red, which could be explained by strict selection to egg quality traits, including optimal shell thickness in this commercial layer breed. These data suggested that CR523443 was a candidate gene for QTL ST53 in the chicken.

Animals↗

PubMed2006

Embryonic exposure to o,p'-DDT causes eggshell thinning and altered shell gland carbonic anhydrase expression in the domestic hen.

The mechanism for contaminant-induced eggshell thinning in wild birds remains to be clarified. It is generally assumed, however, that it results from exposure of the adult laying female. We have reported that embryonic exposure to the synthetic estrogen ethynylestradiol (EE2) results in eggshell thinning in the domestic hen. The objective of this study was to investigate whether eggshell thinning can be induced following in ovo exposure to a bioaccumulating estrogenic environmental contaminant, o,p'-DDT. Ethynylestradiol was used as a positive control. Domestic hens exposed in ovo to o,p'-DDT (37 or 75 microg/g egg) or EE2 (60 ng/g egg) laid eggs with thinner shells than the control birds. The hens from these exposure groups also had a significantly reduced frequency of shell gland capillaries with carbonic anhydrase (CA) activity, a key enzyme in eggshell formation. The decreased number of capillaries with CA activity suggests that a developmentally induced disruption of CA expression in the shell gland was involved in the eggshell thinning found in this study. Egg laying was not affected in hens exposed embryonically to 37 or 75 microg o,p'-DDT/g egg, whereas it was inhibited in hens exposed to higher doses. Decreased lengths of the left oviduct and its infundibulum were seen after embryonic treatment with o,p'-DDT or EE2. In addition, o,p'-DDT exposure resulted in right oviduct retention. The results support our hypothesis that eggshell thinning in avian wildlife can result from a functional malformation in the shell gland, induced by embryonic exposure to estrogenic substances.

Animals↗

PubMed1984

Relationships among fertility, sperm storage, and shell quality.

One hundred and nine White Leghorn hens (50 weeks of age) were used to determine the relationships among fertility, sperm storage, and shell quality. The hens were artificially inseminated (AI) on 2 consecutive days with 100 million spermatozoa per insemination. Eggs were collected for 17 days and were classified as hard shell (HS), thin shell (TS), or shell-less (SL). Specific gravity (SG) was determined on HS eggs. All eggs were incubated for 3 days and broken out to determine fertility. The SL eggs were difficult to incubate; therefore, fertility was not obtained for these eggs. Hens producing eggs with SG less than 1.070 showed a significant (P less than .05) decrease in percent and duration of fertility. Specific gravity was significantly correlated with percent fertility, duration of fertility, and fertile egg production. Following the fertility trial, five hens laying HS and five hens laying SL eggs were inseminated as previously described and were killed on the day after the second insemination. The uterovaginal segments were excised, processed for histological evaluation, and stained for either oil red O to quantitate lipid or hematoxylin and eosin to show sperm distribution in uterovaginal sperm-host glands (UV-SHG). Histological examination of the UV-SHG showed that SL hens had a significantly higher percentage of empty glands than HS hens. However, there were no differences between HS and SL hens for UV-SHG lipid deposition.

Animals↗

PubMed1989

Calcium reserve assembly: a basic structural unit of the calcium reserve system of the hen egg shell.

A well-defined proper subregion of the mammillary knob is described, consisting of baseplate (BP), calcium reserve body (CRB), and an integral but distinct CRB cover. The BP extends 14 to 20 microns into the outer shell membrane and rises a few microns above its surface. The organic matrix of the BP is a composite of modified membrane fibers and adjacent components. The distinct CRB matrix is attached to the BP and extends outward in attenuated from, much like the fractal aggregates associated with filter "cakes." The three regions comprise a unit designated as the CRA (calcium reserve assembly, or assemblies). The CRA are fully developed and mineralized by 10.5 to 11 h postoviposition of the previous egg. By 13 h postoviposition a new structure, the crown, is evident. The classical mammillary knob consists of the CRA/crown complex. By hatch time the CRA are partially decalcified, except in the air cell region. Consequently, a zone of separation develops in the affected CRA about midway through the CRB. Estimates of the calcium recovered from the egg shell and of the calcium found in the CRA, excluding the CRA in the air cell region, indicate that more than enough calcium is present in the CRA to meet the drawdown of calcium from the egg shell by the developing embryo. It is concluded that the CRA that are available to the action of the chorioallantoic membrane represent the calcium reserve of the hen egg shell.

Animals↗

PubMed1999

Short-term effects of a chicken egg shell powder enriched dairy-based products on bone mineral density in persons with osteoporosis or osteopenia.

Based on the high calcium content, chicken egg shells are an interesting source of calcium. We studied the short-term effects on bone mineral density (BMD) of the lumbar spine and hip in 9 women and one man (mean age +/- SD, 63.9 +/- 8.1 years) with osteoporosis or osteopenia. Also the effects on pain and general well-being were monitored. Ten women (62.5 +/- 5.0 years) from a population study on BMD served as a control group. During a study period of 4-8 months, the intervention group consumed twice daily a dairy-based supplement which resulted in a daily intake of, among others, 3.0 g of egg shell powder, 400 IU of vitamin D3 and 400 mg of magnesium. BMD of the lumbar spine (anteroposterior (AP) and lateral (LA) position) and hip were measured by dual-energy X-ray absorptiometry. After the intervention period, BMDs of the lumbar spine, total proximal femur and trochanter were significantly (p < 0.05) increased with (median) 4.4%: (range) 1.7 to 10.4% (lumbar spine AP), 5.7%: -1.3 to 15.9% (lumbar spine LA), 2.2%: -1.9 to 9.4% (total proximal femur), 1.8%: -1.8 to 9.0% (trochanter). Within a period of 4 months, an important reduction in pain was reported and as a consequence an improvement in general well-being. In the control group, BMDs of the lumbar spine AP and of the femoral neck significantly decreased over a period of 8 months with -0.7% (-1.3 to 0.2%) and -0.9% (-2.4 to -0.1%) respectively. Six women of the intervention group continued to use the supplement on their own free will and without any check on compliance, up to 24 months. They consumed the supplement only once daily except for the last three months when they were asked to take the double dosage again. After 24 months BMDs did not differ from baseline. This study shows that egg shell powder is a source of bioavailable calcium. Furthermore, this pilot study indicates that the chicken egg shell powder enriched dairy-based supplement increases BMD of subjects with a low bone mass in the short term and as a consequence delays bone demineralisation for a longer period. (Tab. 3, Fig. 1, Ref. 23.)

Absorptiometry, Photon↗

PubMed1990

Growth of the chick area vasculosa in ovo and in shell-less culture.

The rates of growth and cell proliferation of the chick area vasculosa (Days 2-5 of incubation) were examined in windowed eggs and in shell-less culture preparations. For embryos of developmental Stages 15 to 23, the area vasculosa in shell-less cultures was significantly smaller than in corresponding eggs; however there was no significant difference in the radial growth between these groups. The cultivation of embryos in shell-less culture did not affect the normal macroscopic or histological appearance of the membrane, or the rate of proliferation of its constituent cells, as assessed by tritiated thymidine incorporation. These results indicate that the area vasculosa in shell-less culture provides a suitable assay of factors which regulate angiogenesis.

Animals↗

PubMed1991

Microbial barrier properties of hen egg shells.

Scanning electron micrographs of shell surfaces revealed a highly fissured outer layer with few open pores on brown eggs but many on white eggs. Total removal of the cuticle with solvents was difficult but partial removal with surface etching was possible using concentrated nitric acid. Staining methods to estimate the number of pores were unsatisfactory but it was possible to detect and count pores on micrographs, as pore mouths were usually associated with depressions and cuticle disruptions. Additionally, porosity could be estimated by measuring the distance between pores along fractured edges of samples. Egg shell contents were replaced with nutrient agar and incubated in Escherichia coli broth. Colonies were subsequently isolated from the agar, indicating that the barrier properties of shells and membranes had been compromised. Experiments with isolated inner shell membranes showed that these posed no significant barrier to E. coli. The exposure of whole intact eggs to E. coli broth followed by seep filtration and microbiological analysis of egg contents, indicated that bacteria had entered the eggs. The degree of infection was correlated with the pole of the egg in contact with the E. coli broth and was attributed to the increased porosity of the blunt pole of the egg compared with that of the apex. Similar experiments immersing eggs into broth inoculated with a Salmonella strain resulted in contamination of the egg contents with this organism.

Animals↗

PubMed1987

Effect of calcium supplementation on growth of shell-less cultured chick embryos.

Chick embryos grown in shell-less culture are calcium-deficient by 9 days and retarded in growth by 13 days of incubation (Dunn and Boone, Poult. Sci., 56:662-672, 1977). To determine whether addition of exogenous calcium might stimulate growth and/or survival of cultured embryos, calcium supplementation was attempted. Calcium supplementation between days 11 and 17 resulted in significant increases in both total embryo and serum calcium. Addition of shell pieces oriented with shell membranes onto the chorioallantoic membrane (CAM) resulted in significant stimulation of calcium transport by the CAM. However, growth of supplemented embryos was not increased to the same degree as were embryonic serum and total calcium levels. It is concluded that at least one factor other than calcium deficiency is responsible for retarded growth of shell-less cultured embryos.

Animals↗

PubMed1983

Supplemented eggshell restores calcium transport in chorioallantoic membrane of cultured shell-less chick embryos.

It was previously reported (Tuan, 1980a) that the development-specific expression of calcium transport and related functions in the chick embryonic chorioallantoic membrane (CAM) requires the continuous presence of the eggshell, the calcium source of the embryo. To further understand the mechanism of action of the eggshell on the CAM functions, this study reports the effects of eggshell supplementation on chick embryos maintained in shell-less cultures. The cultured embryos were able to accumulate and utilize the exogenous shell calcium, applied directly onto the CAM, for skeletal formation. In the region of the CAM directly adhering to the added shell, calcium transport activity, calcium-binding protein (CaBP) activity, and vitamin K-dependent gamma-glutamyl carboxylase activity were significantly restored. These results strongly suggest that the proximity of shell calcium may regulate expression of calcium transport and related functions in the chick embryonic CAM.

Allantois↗