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At least 55 records · Page 3Linked to original sources
PubMed1977

The effect on egg-shell thickness of the inclusion of the calcinogenic plant Solanum malacoxylon in the diet of laying hens.

The leaves of the plant Solanum malacoxylon contain 1,25 dihydroxycholecalciferol, the active form of vitamin D. The effect on egg-shell thickness of supplementing the diet of laying hens with a dry powdered preparation of the leaves (DLSM) has been studied. A significnat increase in shell thickness was evident for eggs laid on the second and subsequent days of the DLSM-regimen but nor for those laid during the first 24 hours. It is suggested that the provision of high doses of the vitamin D metabolite in the form of a DLSM supplement may restore calcium binding protein levels in birds approaching the end of the first laying year and hence improve dietary calcium absorption and consequently egg-shell quality.

Animals↗
PubMed1991

[Chick embryo culture using duck egg shell--first successful hatch ].

The suitability of duck egg shell (DES) for chick embryo culture was investigated. Chick embryos were transferred into DESs with all egg contents after 3 days of normal incubation and cultured. The vessels made of polyethylene cling film were used for shell-less control. Among 35 embryos cultured in DESs, 21 survived until 16 days of incubation (13 days after transfer) and finally 3 newly hatched chicks were obtained at 22 days of incubation. One of them died 4 days later, but remaining two became full-grown cocks showing normal body weight and production of fertile sperms. Among 37 embryos cultured in polyethylene vessels, none survived over the period of 19 days of incubation. It is suggested that DES culture system may be useful for the various experiments using chick embryos.

Animals↗
PubMed1992

Is there lipid peroxidation induced malondialdehyde production during egg shell formation?

The marked increase observed in malondialdehyde concentration of the blood plasma and liver of laying hens during egg shell formation in a previous experiment (Mézes and Lencsés, 1985) were explained as a possible consequence of physiologically controlled lipid peroxidation. In this experiment, 54-week-old laying hens were treated intrauterinally with indomethacin (1.0 and 2.0 mg/kg body mass) after oviposition. Two other groups of hens were treated per os with excess amounts of vitamin E (100 and 200 mg/bird). The higher dose of indomethacin significantly decreased the PGF2 alpha production and malondialdehyde content of the sell gland, as well as the malondialdehyde concentration of the plasma. The excess amount of vitamin E had the same effect. The results suggest that during egg shell formation malondialdehyde is derived from prostanoid biosynthesis rather than from a free-radical initiated lipid peroxidative process. On the other hand, the excess amount of vitamin E inhibited prostaglandin biosynthesis as well as malondialdehyde production.

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↗
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↗
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↗
PubMed1976

The development of the oxygen permeability of the avian egg shell and its membranes during incubation.

The 02-permeability of the avian egg shell and shell membranes is initially low (approximately equal to 0.1-10(-6) ml O2 STP-sec-1cm-2-mmHg-1) during incubation but increases about 10-fold after the first week. This increase correlates with a decline in water content of the membranes. A major increase in colloid osmotic pressure (up to 50 cm Hg) occurs and is the suggested cause for the onset of rapid removal of water from the membranes. A high membrane water content correlates with low O2-permeability and vice versa. The final degree of membrane hydration reached during incubation is independent of ambient humidity; that is, the O2-permeability of the shell and its membranes is controlled by conditions inside the egg. An hypothesis is presented to explain the profound increase in O2-permeability while the rate of water loss from the egg remains stable during incubation. The removal of water from the shell membranes by the increased colloid osmotic pressure will increase the number of gas filled channels in the membranes which in turn will increase the O2-permeability. In spite of the change in water content, the water vapor pressure in the shell membranes will always be very close to that of a free water surface and water loss will hence be determined by the ambient humidity and the porosity of the mineral shell.

Animals↗
PubMed1985

[Structure of the hen's egg shell and its changes during incubation. A scanning electron microscope study].

The structure of the hen's egg shell was studied during the incubation. The local differences in the structure of the shell were estimated during the incubation in dependence to the development of the allantochorial vascular system. On the external surface of the shell there is a thin layer, homogenous in the SEM. It remains changeless during the whole period of incubation. The main part of shell is formed by long prisms with their long axes oriented perpendicularly to the external surface of the shell. These prisms are partially twisted round each other, similarly as in the case of the teeth enamel. The inner layer of the shell is formed by a system of fibers forming the three-dimensional network, similar to an air filter. In the middle of incubation, when the embryo's skeleton is still predominantly cartilaginous, is the structure of the shell identical with that one at the beginning of incubation. At the end of incubation, when the embryo's skeleton is already predominantly ossificated, the inner layer of the shell disappears without any trace. By resorption of the shell are the peaks of the prisms of the middle layer of the shell destroyed as well. The above described changes are the best visible in the equator region of the shell. Less developed are they in the region of the sharp pole of the egg. They are not detectable in the region of the blunt pole of the egg. In this region the egg's shell has the same structure during the whole period of incubation. The changes of structure of the shell--the resorption of the inner layer together with partial destruction of the prisms of the middle layer - exactly correspond with extension of the allantochorial vascular system.

Animals↗
PubMed1992

Nutritional and environmental factors involved in egg shell quality of laying hens.

1. Two experiments were conducted to assess the effects of lighting regime, dietary calcium source and sodium bicarbonate on production variables and egg shell quality of White Leghorn hens. In both experiments, hens were assigned to one of three lighting programmes that provided evening, morning or intermittent (midnight) lighting supplements in addition to natural daylight. Experimental diets used in the first study were formulated to contain (1) ground oyster shell flour, (2) limestone flour, or (3) and (4) the same +2/3 of the calcium source as hen-size oyster shell grit. The same 4 diets plus those containing hen-size limestone or hen-size limestone and oyster shells were used in experiment II. Additionally, diets in the first experiment contained either 0 or 10 g/kg sodium bicarbonate. 2. Hen-day egg production and food consumption were not affected by any of the experimental treatments. Hens fed on oyster shell diets or exposed to intermittent lighting regimes laid eggs of the highest specific gravity. Shell quality, as measured by specific gravity, was not affected by the addition of dietary sodium bicarbonate. 3. As expected, elevated temperatures (greater than 32 degrees C) significantly reduced egg shell quality. However, this effect was variable particularly in experiment II which used younger hens. 4. The shell quality of eggs from hens exposed to intermittent lighting in experiment II was significantly higher in each of the 4 sampling periods: morning (08.00-12.00), afternoon (12.00-16.00), evening (16.00-20.00) and night (20.00-08.00). 5. It is suggested that midnight lighting programmes provide a means of supporting egg shell quality of older laying hens during the summer months without a significant reduction in egg production.

Animal Nutritional Physiological Phenomena↗
PubMed1976

The isolation and characterisation of hyaluronic acid in egg shell.

Analysis showed that the organic part of the chicken's egg shell consisted of a series of proteins and polysaccharides, probably present as glycoproteins and glycosaminoglycans. A purified preparation of a glycosaminoglycan (minimum mol. wt. 25 000), homogeneous by sedimentation velocity analysis and sedimentation to equilibrium in a density gradient, contained equimolar amounts of N-acetylglucosamine (36.3% s/w) and glucuronic acid 35.6% w/w). Digestion with testicular and streptomyces hyaluronidases and identification of the degradation products showed the glycosaminoglycan to be hyaluronidases and identification of the degradation products showed the glycosaminoglycan to be hyaluronic acid.

Acetylglucosamine↗
PubMed1977

A nutrient re-evaluation of shell eggs.

Most data on the nutrient composition of shell eggs were obtained before 1950. Since then, management systems for egg production and analytical methods for many components have changed. Freeze-dried whole egg, yolk and white samples were prepared from eggs obtained from a single source of 15 month old White Leghorns. The sample were packaged under nitrogen and held at -20 degrees C. until analyzed. Conversion factors are included for expressing the amount of each component on a per egg as well as a per 100 g. edible liquid basis. This re-evaluation of nutrient data included total solids, lipid, protein, cholesterol, ash, calories, amino acids, fatty acids, vitamins and minerals.

Amino Acids↗
PubMed1991

Modulation of quail intestinal and egg shell gland calbindin (Mr 28,000) gene expression by vitamin D3, 1,25-dihydroxyvitamin D3 and egg laying.

The effects of vitamin D3 sources, egg production and egg cycle on the genomic expression of calbindin (Mr 28,000) in the intestine and egg shell gland (ESG) of quail were characterized by Northern blot and solution hybridization, using synthetic oligonucleotide probe. In vitamin D3- or 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3)-fed quail, onset of egg production induced duodenal and ESG calbindin mRNA and calbindin synthesis. Duodenal calbindin mRNA was slightly higher during the period of shell calcification as compared with the period during which shells were not formed (ESG inactivity). ESG calbindin mRNA was markedly higher during the period of shell calcification than of ESG inactivity. Increasing dietary intake of [3H]1 alpha-hydroxyvitamin D3 increased the duodenal, but not ESG, content of 1,25-(OH)2D3 and calbindin. Duodenal calbindin and its mRNA were absent in vitamin D-deficient quail and were not affected by egg laying. ESG calbindin in the vitamin D-deficient quail was not affected by egg laying, but calbindin mRNA increased in the vitamin D-deficient birds during shell calcification. The results suggest that: (a) intestinal calbindin mRNA and calbindin are induced and/or regulated, either directly or indirectly, by 1,25-(OH)2D3; (b) intestinal calbindin and its mRNA are further induced at the onset of egg laying by an additional stimulator besides 1,25-(OH)2D3; (c) 1,25-(OH)2D3 is required for the expression of the latter stimulator; (d) ESG calbindin mRNA and calbindin are induced in egg-laying birds by a stimulator associated with the egg cycle; and (e) the induction of ESG calbindin mRNA does not need vitamin D metabolites, but 1,25-(OH)2D3 is required for the translation of the mRNA.

Animals↗
PubMed1989

Characterization of electrolytes and protein content in isthmic and uterine flushings from hens laying shell-less versus hard-shell eggs.

In Experiment 1, hens laying hard-shell (HS) eggs were sacrificed at each of eight stages of egg formation including oviposition (0 h) and 1, 4, 8, 12, 16, 20, and 24 h after oviposition. In Experiment 2, hens laying either shell-less (SL) or HS eggs were sacrificed at four stages of egg formation (oviposition, 4, 8, and 20 h after oviposition). The isthmus and uterus were flushed with 6 and 10 mL of cold .85% NaCl, respectively, and electrolyte contents were determined. Total flushing contents of calcium, potassium, and magnesium were higher (P less than or equal to .01) in uterine than in isthmic flushings (Experiment 1). In every case, an interaction (P less than or equal to .01) between time of collection and organ (isthmus and uterus) was found, indicating that patterns of change in flushing content of each electrolyte differed in the two organs over time in birds laying HS eggs. In Experiment 2, total recoverable calcium, magnesium, potassium, and total protein were higher in uterine than isthmic flushings (P less than .01). Interactions between time of collection (0, 4, 8, and 20 h) and treatment group (SL or HS) were observed for all electrolytes measured in uterine flushings. Results suggest that calcium, required for shell calcification, does not appear in the isthmic or uterine lumen or both at an appropriate time in SL hens. Thus, production of SL eggs may be related to mechanisms regulating patterns of change or ratios of electrolytes (calcium, magnesium, potassium) or both in the isthmus or uterus of the laying hen.

Animals↗