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At least 685 records · Page 38Linked to original sources
PubMed2000

Ultrastructural characteristics of ostrich eggshell: outer shell membrane and the calcified layers.

The ultrastructure of the eggshell of the domestic hen has been well researched and structural studies of other avian species, such as the ostrich, often base their interpretation of egg shell structure on that of the chicken. In the ostrich, lowered hatchability and hatching trauma may be due to shell ultrastructural abnormalities. In the present study the ultrastructure of the calcified portion, and the outer shell membrane (OSM), of domesticated ostrich eggshells was investigated using standard electron microscopic techniques. Transmission and scanning electron microscopy studies demonstrated intimate contact between cup-shaped structures present on the OSM and the mammillary layer of the calcified portion of the shell. The initial calcium carbonate growth of the calcified shell was of a dendritic nature with nucleation sites on the surface of the cup's contents. The dendritic growth gave way to a more randomly-orientated, smaller crystallite growth structure, which changed in form as it neared the vertical crystal layer (VCL). The VCL is described as being both amorphous and 'crumbly' depending on the plane of fracture. These observations suggest that firstly, initial calcification is contained within the cups and is then directed outwards to form the shell and that secondly, the VCL may contain an evolutionary, calcified cuticular layer. These observations serve as a baseline for studies investigating the effect of shell structure and strength on hatchling trauma and the influence of maternal diet.

Animals↗
PubMed1999

Relationships among age, eggshell thickness and vitamin D metabolism and its expression in the laying hen.

Hens forming uncalcified shells synthesized less 1,25-hydroxycholecalciferol (1,25(OH)2D3) and less duodenal and eggshell gland (ESG) calbindin than normal laying hens. Hens forming thin shells had lower intestinal and ESG calbindin and its mRNA. Reducing ESG calcium (Ca2+) transport by the carbonic anhydrase inhibitor acetazolamide, but not by dietary Ca2+ restriction, reduced ESG calbindin and its mRNA. Two sub-populations of hens characterized by shell thickness (ST) maintained this characteristic throughout the whole production period. The differences between the two sub-populations increased with age. In old laying hens, the two sub-populations responded differently to dietary Ca2+ restriction and to exogenous 1,25(OH)2D3. Those forming a thin shell responded to 1,25(OH)2D3 by a significant improvement in ST. The results suggest that: (a) the mechanism responsible for Ca2+ transport to the egg shell consists of a vitamin D-dependent absorption of Ca2+ and a multi-factor-dependent transfer of Ca2+ to the shell; (b) both steps are, most likely, calbindin-mediated; however, the induction of calbindin gene expression in the ESG is predominantly calcium-dependent; and (c) the apparent defect in vitamin D metabolism or its expression in old hens is typical of, or even exclusive, to thin-shell-forming hens.

Acetazolamide↗
PubMed1979

Effect of diurnal or nocturnal heat stress on egg formation.

1. Mature laying hens were subjected to ambient temperatures sufficient to maintain body temperature of 43 degrees C for periods of 6 to 7 h during the day (eight periods) or the night (five periods). This did not reduce total daily food consumption. 2. The effect of heat stress during the day was mostly on egg-shell quality, being adverse and significant. During the night heat stress caused a significant decrease in egg production, its effect during the day was less marked in this respect. 3. Heat stress thus seems mostly to affect the early stages of shell formation, while its effect on egg production seems to depend on the time at which it occurs in relation to ovulation. 4. These results suggest that egg production is directly affected by heat stress; prolonged heat stress probably also acts indirectly, by suppression of food intake.

Animals↗
PubMed1989

Modelling the relationships of egg weight, specific gravity, shell calcium and shell thickness.

1. The relationships between egg weight, egg specific gravity, shell weight, shell calcium and shell thickness of 800 eggs from 8 treatments were expressed using mathematical models. 2. The equations describing the relationships were on the basis of any two independent variables predicting the remainder. 3. Of 10 possible models, 4 had high co-efficients of determination (R2 greater than 0.80) for each predicted dependent variable. 4. The two independent variables in each of these 4 models were, in turn, egg weight and specific gravity, egg weight and shell weight, egg weight and shell thickness, and specific gravity and shell weight. 5. The best model was that having egg weight and specific gravity as independent variables, with R2 values of 0.94, 0.88, and 0.85 for predicted shell weight, shell calcium, and shell thickness, respectively. Moreover, egg characteristics can be measured non-destructively by this model, whereas the other three require destruction of the egg.

Age Factors↗
PubMed2000

Characterisation of proteases involved in egg hatching of the sheep blowfly, Lucilia cuprina.

A number of proteases were identified in the egg shell washings (ESW) collected during the egg hatching of Lucilia cuprina (sheep blowfly). Characterization of these proteases indicated a pH optima in a similar pH range that was optimal for L. cuprina egg hatching. Mechanistic characterization of these proteases indicated that they were predominantly of the serine class. Several protease inhibitors were tested for their ability to inhibit L. cuprina egg hatching in vitro. Egg hatching was significantly (P<0.05) inhibited by PMSF (61%), 1,10-Phenanthroline (42%) and Pepstatin (29%). The inhibition of egg hatching by PMSF showed a strong concentration dependence, with its effects ranging from inhibition at high concentrations to enhancement of egg hatching at low concentrations. Addition of ESW to unhatched eggs, significantly (P<0.05) enhanced their rate of hatching above untreated control eggs. This enhancement of egg hatching was significantly (P<0.05) reversed by the protease inhibitors Elastatinal (40%), 1,10-Phenanthroline (40%) and PMSF (38%). These studies indicate a role for serine and/or metallo-proteases in facilitating L. cuprina egg hatch.

Animals↗
PubMed1979

Production of 1,25-dihydroxyvitamin D3 and formation of medullary bone in the egg-laying hen.

Renal 25-hydroxyvitamin D-1-hydroxylase, the percentage of medullary bone in the femur, plasma calcium, and plasma phosphorus were measured in female chickens reaching maturity. These parameters and plasma 1,25-dihydroxyvitamin D levels were also measured during the daily egg-laying cycle in mature hens. The renal 25-hydroxyvitamin D3-l-hydroxylase becomes elevated in maturing hens before and at the time of ovulation. This elevation in the 1-hydroxylase correlates with the elevation in total plasma calcium concentration but lags and at the time of ovulation and is followed by a further elevation of plasma 1,25-dihydroxyvitamin D levels. The plasma 1,25-dihydroxyvitamin D level remains high until 12 h postovulation. At this time, it falls to the preovulation level. No relationship could be found between the plasma 1,25-dihydroxyvitamin D levels and the changes in medullary bone found during the egg-laying cycle. However, plasma 1,25-dihydroxyvitamin D levels are highest immediately before and during the egg shell calcification phase of the egg-laying cycle.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1980

Jejunal calcium permeability in laying hens during egg formation.

The permeability of the upper jejunum to water, calcium, potassium, sodium and chloride was measured in the immature pullet and then in the laying hen before and during egg-shell calcification by an in vivo perfusion procedure. Jejunal calcium permeability was constant throughout egg formation. Thus, the increase of net absorption during shell calcification was not due to enhanced mucosal capacity for calcium translocation, but rather to a better solubilization of calcium carbonate in the upper digestive tract. However, this capacity increased at the onset of egg production, as shown by the difference between immature and mature birds.

Animals↗
PubMed1978

[Epizootic of S. heidelberg in poultry breeding flocks raised commercially].

It was noted that under the conditions of industrial raising of adult birds the epizootic of Salmonella heidelberg could assumme an acute course with a clinical manifestation. After its short-term acute manifestation the infection acquired a protracted course. Mortality correlated directly with the age of the birds. Isolated and identified were a total of 117 Salmonella heidelberg strains from carcasses, cloacal samples, eggs, and litter. Regardless of the short-term Salmonella harbouring the deep litter was shown to predispose to reinfections. The isolation of eight strains of S. heidelberg from the egg shell and the yolk of freshly laid eggs as well as the negative microbial findings in one- and two-fold fumigated eggs corroborate the idea of the additional entering of Salmonella organisms through the shell. These also point to the fact that fumigation carried out up to the third hour following laying may contribute to the raising of disease-free broilers. Treatment with furazolidon and chloramphenicol in combination or the application of salmocid at the rate of 250 milligram microgram of feed in the course of ten days suppresses the acute manifestation of the disease and restores the productivity of birds, having no effect on the harbouring of the infection in the flock.

Animals↗
PubMed1979

Chlorinated pesticide residues in chicken egg.

Two hundred and twenty-one representative samples of chicken eggs of native and commercial strains of Gallus domesticus were collected during January 1975 to August 1977 throughout the Tehran area and the Northern province of Mazandarane. The samples were analyzed for chlorinated pesticide residues by gas-liquid chromatography. The insecticides [1,1,1-Trichloro-2,2-bis (P-Chlorophenyl)ethanel] (DDT), [1,1-Dichloro-2,2-bis (P-Chlorophenyl) ethane] (TDE), [1,1-Dichloro-2,2-bis (P-Chlorophenyl)ethylene] (DDE), isomers of benzene hexachloride (BHC), Aldrin/Dieldrin, Heptachlor/Heptachlor epoxide, Dieldrin, and endrin were detected in varying concentration in the eggs. The eggs of native bred chickens, mainly as a result of their food sources, showed greater concentration of all pesticides except BHC isomers than those of commercial types. Though concentration of DDT compounds in 22% of native bred and 5% of commercial eggs exceeded WHO tolerance limit, the mean concentrations of pesticides residues were not exceeding these limits. There was no correlation between concentrations of pesticides and egg shell thinning.

Aldrin↗
PubMed1976

Hatching of Schistosoma mansoni eggs and observations on motility of miracidia.

Eggs of Schistosoma mansoni were obtained from livers of mice and hatching was observed under varying conditions of light and ionic composition of the medium. Hatching occurred equally well in light and in darkness. Eggs also hatched readily in 1- to 50-m OsM solutions of urea, sucrose, sodium chloride, and glycerol, but hatching was inhibited at higher concentrations unless the eggs were left in solutions for long periods of time. Hatching readily occurred in deionized water, but the emerged miracidia did not swim longer than 5 to 10 min unless Na+ was added. Histochemistry of the egg showed DNA-positive egg granules and a polysaccharide-positive vacuole matrix. Acid mucopolysaccharides were stained in the vacuolar matrix and in the anterior sac of the miracidium. Longitudinal alignment of constituents of the egg shell is suggested by the predominance of longitudinal rents in the shell at hatching. A mechanism of hatching involving an osmotic stimulus is proposed.

Animals↗
PubMed2005

Acute depigmentation of fertile brown eggs in a commercial layer operation.

Rapid depigmentation of brown eggs is an infrequent but startling event in the commercial egg industry that can result in significant economic losses. Loss of shell pigment in brown-shelled eggs is caused by various factors. In many cases, the exact cause of flock-wide pigment loss remains undetermined. A rapid decline in shell pigmentation was observed in 2 flocks of Hyline brown layers. The lack of evidence of an infectious disease process suggested a feed or management problem. On the basis of a small-scale, "in-house" feeding trial, the feed was identified as the cause of depigmentation. Feed analysis by liquid chromatography with mass spectrometry confirmed the presence of 4,4'-dinitrocarbanilide, a major component of nicarbazin (NCZ). There was no evidence of increased mortality, and only a slight but transient drop in the egg production was observed. Depigmentation effects were rapidly reversed after replacing the feed with NCZ-free feed.

Animal Feed↗
PubMed1984

Effects of suppression of eggshell calcification and of 1,25(OH)2D3 on Mg2+, Ca2+ and Mg2+HCO-3 ATPase, alkaline phosphatase, carbonic anhydrase and CaBP levels--II. The laying hen intestine.

Activity of a HCO-3 stimulated Mg2+ dependent ATPase is demonstrated in mitochondrial fractions of the avian duodenum. Suppression of eggshell calcification resulted in a slight reduction in Mg2+, Ca2+ and Mg2+HCO-3 ATPase activities. Duodenal carbonic anhydrase activity was lower in birds laying soft-shelled eggs than in birds laying normal eggs. Alkaline phosphatase and calcium binding protein levels both decreased along the length of the small intestine, but the effect was more pronounced for alkaline phosphatase. Suppression of eggshell calcification and treatment of shell-less laying hens with 1,25(OH)2D3 influenced alkaline phosphatase activity only in the duodenal mucosa. Suppression of eggshell calcification reduced CaBP levels in all sections of the intestine. Treatment with 1,25(OH)2D3 restored CaBP levels. Regulation of intestinal CaBP levels by 1,25(OH)2D3 would therefore, seem to be controlled more directly by calcium requirements associated with eggshell calcification than by gonadal hormones.

Adenosine Triphosphatases↗
PubMed1991

The influence of egg sequence position on fertility, embryo viability, and embryo weight in broiler breeders.

A study was undertaken to determine whether fertility, early embryo viability, and the weight of the egg, shell, and embryo are influenced by the position of an egg in a laying sequence. One hundred and three Indian River broiler breeder hens were housed individually in cages at 21 wk of age. Beginning at 43 wk of age, each hen was inseminated once per week, with 50 microL of fresh undiluted pooled semen from Indian River broiler breeder males. Beginning at 45 wk of age, and for the following 45 days, all eggs laid were collected. Eggs were collected hourly for 8 h after "lights on" and a final daily collection was made 14 h after lights on. Each egg was classified as "first-of-sequence" or "subsequent". Eggs were weighed and placed in a forced-air incubator twice per week. After 168 h of incubation, the eggs were removed from the incubator, weighed and assessed for fertility and embryo viability status. The embryo was also weighed. Shell weight was recorded after 3 to 4 days of air drying. Egg weight was significantly greater in first-of-sequence compared with subsequent eggs. First-of-sequence eggs exhibited significantly smaller Day 7 embryos (on a percentage basis), lower shell weight (on a percentage basis), and significantly less egg weight loss during the 7 day incubation period (absolute and percentage basis) than did subsequent eggs on a sequence. Least squares (LS) means for fertility did not differ significantly between first (87.02%) and subsequent (89.56%) eggs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

Effects of PCBs, DDT, and mercury compounds upon egg production, hatchability and shell quality in chickens and Japanese quail.

Dietary polychlorinated biphenyls (PCBs), DDT and related compounds, in well controlled experiments, produced no detrimental effects upon egg shell quality in Single Comb White Leghorm chickens or in Japanese quail. PCBs caused some decrease in egg production and a drastic reduction in hatchability in chickens, but not in Japanese quail. Inorganic mercury as HgSO4 or HgCl2, at dietary levels up to 200 p.p.m. of Hg, had only small effects, if any, upon egg production, hatchability, shell quality, morbidity and mortality. However, methyl mercury chloride at levels which provided 10 or 20 mg. of Hg per kg. of diet caused severe effects upon egg weight, egg production, fertility, hatchability, egg shell strength, morbidity and mortality. The results of these experiments demonstrate that the decrease in egg shell quality which has occurred in eggs of White Leghorn hens over the past three decades is not due to contamination of commercial feeds with DDT or its derivatives, or with PCBs. The extent to which environmental contamination with methyl mercury is responsible for decreased egg shell strength in commercial laying hens, and possible synergistic relationships between methyl mercury, DDT, DDE and PCBs in reducing egg production, hatchability and shell strength, remain to be determined.

Adipose Tissue↗
PubMed1980

Urinary excretion of calcium in the presence or absence of shell formation by chickens producing thick or thin shells.

The pattern of urinary calcium excretion before and during shell formation was observed for White Leghorn chickens producing thick or thin shelled eggs. Urine samples were collected at 2.5, 7.5, 12.5, and 20 hr after oviposition. Urine was collected in a tube inserted to cover both ureters within the cloaca and calcium levels were determined by atomic absorption. Urinary calcium was found to decrease similarly in both shell lines from 44 mg % to 5 to 6 mg % during shell formation. When no shell was being produced, hens of both shell lines excreted calcium in the urine at 34 to 53 mg % levels throughout the 20-hr period.

Animals↗