For shells filed on the outside and snapped outwards or filed on the inside and snapped inwards there was a very significant relationship between S and T 2. For shells filed on the inside and snapped outwards, the mammillary knobs made no contribution to strength and it was only after these had been filed off that a typical relationship between S and T 2 developed.
Shells filed on the outside and snapped inwards gave very variable results in relation to the removal of the first layers of shell. In some cases the removal of a thin outer layer increased the strength and in other cases it decreased it and it was only later that a steady relationship between S and T 2 developed.
In general the egg shells of the domestic fowl became weaker towards the inside of the shell. 相似文献
It was found that when strips of shell of standard length and width were filed on the inside and snapped inwards, or filed on the outside and snapped outwards, then there was a rectilinear relationship between strength and the square of the thickness. When shells were filed on the inside and snapped outwards, the shell strength remained constant until quite a large fraction had been filed away, then the typical rectilinear relationship appeared. When shells were filed on the outside and snapped inwards, the removal of a little of the shell resulted in an increase in strength before the rectilinear relationship appeared. These results are discussed in relation to shell structure.
The use of concentrated hydrochloric acid to thin the shell was unsuccessful because it weakened the remaining shell far more than filing did. Treatment of the shell with boiling sodium hydroxide solution (10 per cent) either before or after filing, showed that the alkali is able to penetrate a complete shell as readily as it can penetrate into one which has been filed, and that the shell is weakened. 相似文献
2. It was found that moisture content, temperature and load rate have important effects on shell properties ; both the strength and stiffness of the shell are greater in snapping‐inward tests than in snapping‐outward tests; residual stress exists in the egg shell; the correlation between failure moment and shell thickness was highly significant, on average about 0.9, and was dependent on the spread in the thickness data.
3. Estimates were made of the ultimate strength and Young's modulus of egg shell material and it is concluded that a substantial size effect exists in the egg shell. 相似文献
2. The water vapour conductance of fowl and Muscovy duck egg shells was not affected by the treatment.
3. Cuticle removal increased the conductance of turkey and goose shells, particularly those already relatively porous to water vapour.
4. Removal of cuticles from domestic duck egg shells increased water vapour conductance. In this case the effect was most marked for eggs with lower initial conductances.
5. The differing patterns of resistance to water vapour loss associated with egg shell cuticle are related to the ultrastructure of the cuticle itself, especially the number and size of cuticular fissures.
6. The results suggest that egg shell cuticle is a component in a series of resistances associated with the egg shell and that the use of Fick's Law is insufficient to explain water vapour diffusion across the shell.
7. Embryo survival may be improved by cuticle removal, though this may be limited to those species in which the cuticle restricts water vapour loss in initially low conductance egg shells. 相似文献
2. Sulphanilamide appeared to act mainly by reducing the rate of shell deposition, time spent in the shell gland was unaffected.
3. The thickness of shell components was reduced in a roughly proportional manner in thin shells produced during sulphanilamide treatment.
4. It is proposed that other thin shells in which the component layers are all reduced to a similar extent are also the result of a decreased deposition rate. 相似文献
2. In the rabbit osmolality of the fluids from the different segments of the digestive tract was similar (331 ± 12 mOsm) and slightly hypertonic to blood plasma (297 ± 0.12 mOsm).
3. In the hen osmotic pressures were: crop 537, gizzard 312, duodenum 571, proximal jejunum 650, distal jejunum 573, proximal ileum 514 and distal ileum 451 mOsm. Only osmolality of the crop contents was influenced by egg formation.
4. In the cockerel osmotic pressure in the alimentary tract followed the same pattern as the hen and was modified by the time of day.
5. Plasma osmolality in the fowl was about 320 mOsm. Absorption of water across the proximal jejunum is achieved therefore against a gradient of about 330 mOsm in the female and 420 mOsm in the male fowl. 相似文献
2. The shell thickness increased and the area density of pores decreased from the blunt to the pointed end of the egg. During incubation, shell thickness decreased, but the shell diffusive conductance to water vapour (GH2O) remained constant.
3. Fresh egg mass (m0), length and breadth of the egg, GH2O and specific water vapour conductance, spGH2O (GH2O per g of m0 ), were affected by the age of the laying flock.
4. Eggs of the domestic guinea fowl were bigger and heavier than eggs of the wild one.
5. Allometry showed that guinea fowl eggs differ from those of the other birds by their greater shell thickness and density of pores. However spGH2O was normal, the thickness of the shell being compensated for by a greater density of pores for gas exchanges. 相似文献
2. The shells of such eggs were thinner than those of intact eggs in seven of the populations.
3. The number of defective eggs, the specific gravity of the eggs, and the percentage hen‐day egg production of normal eggs were significantly correlated within populations with the incidence of broken eggs.
4. No significant correlations were found within populations between the incidence of egg breakage and either egg weight, body weight, or shank length. 相似文献
2. Three‐ to four‐fold increases in blood flow were found in segments surrounding the egg during its passage along the oviduct, possibly due to an enhanced metabolic activity in the muscle layer of the oviduct.
3. Shell‐gland blood flow was minimal in the absence of an egg and increased gradually to a maximum (5‐fold) about 5 h after entrance of the egg into the shell gland. This parallels the rate of calcification of the egg shell.
4. Changes in blood flow in the ovarian follicles and other parts of the oviduct were small while the egg was in the shell gland. This might be typical for the reproductive system of the fowl, which undergoes little structural alteration during egg formation. 相似文献
2. Yolk cholesterol concentration decreases between 20 and 30 weeks of age, and then remains constant until 70 weeks of age. Yolk total lipid concentration increases to a maximum at 40 weeks of age before decreasing to its original value at 60 and 70 weeks of age.
3. Bird means for yolk cholesterol and total lipid concentration are negatively related at 20 weeks of age, and essentially independent for the remainder of the first year of egg production.
4. Variation for yolk cholesterol concentration between 30 and 70 weeks of age appears to be a consequence of differences in the proportion of cholesterol to other lipid components.
5. Uptake of plasma lipoproteins characteristic of the immature bird is likely to be responsible for the high yolk cholesterol concentration at 20 weeks of age. 相似文献
Suitably prepared radial and tangential sections of these egg shells have been examined by polarised light and by histological staining techniques.
It was shown that these shells contained flaws which consisted of abnormal crystals embedded in the normal crystalline structure. The flaws contained abnormal organic material. 相似文献
2. The Sinai egg was smaller and its shell thicker and stronger than the Leghorn egg. All the differences were statistically significant.
3. Shell thickness and strength of Leghorn eggs were in accordance with values predicted on the basis of egg mass, while those of the Sinai and the two crosses were considerably higher than predicted.
4. The apparent differences in mean egg mass between Sinai and Leghorn breeds did not explain the differences in egg‐shell quality, neither did the shape index which was very similar among all breeds.
5. The findings suggest that the differences in egg‐shell properties are of a genetic origin.
6. The thick, strong and less permeable egg‐shell of the Sinai breed may reflect adaptations to its arid environmental origin and to incubation in the open.
7. These genetically‐determined egg‐shell characteristics might serve in a future selection for improved egg‐shell quality in poultry. 相似文献
2. The yolk: albumen ratio of the goose egg was higher.
3. The fat concentration in the egg yolk and the protein concentration in the egg albumen were lower.
4. Deposition of dry matter in the embryo and energy expenditure during incubation were similar. In both species, the nitrogen in the embryo exceeded the nitrogen in the egg contents. This is probably due to the utilisation of egg‐shell membrane proteins.
5. Lysine concentration in the goose egg proteins was lower, which was reflected in the hatched gosling proteins.
6. There were high correlations in amino acid concentrations between chicken and goose eggs and between the efficiencies of amino acid utilisation by their embryos, implying that similar metabolic processes are involved in these two species. 相似文献
2. A reduction in egg number, egg mass, egg shell thickness and egg shell magnesium content occurred in birds receiving diets containing either 207 or 132 mg Mg2+/kg even though the duration of egg formation was unaffected.
3. The progressive increase in magnesium content normally observed towards the outer surface of the hen's egg shell was not present in birds receiving a diet containing 207 mg Mg2+/kg. 相似文献
2. There was evidence that eggs from range had stronger shells: they required more energy to crack, shell thickness was greater and shell deformation at 70 weeks was less (though the difference was not significant).
3. The differences between systems in shell strength, although real, were small. It is probable that environmental insults make a much larger contribution than shell strength to differences in crack incidence.
4. Eggs laid by hens on range were larger (+ 6.8% at 36 weeks and + 2.9% at 70 weeks) than those laid by the same stock housed in cages. 相似文献
2. The Sinai egg was found to be smaller and less permeable to water vapour than the eggs of the Leghorn and crossbreds. The differences were statistically significant.
3. The measured egg‐shell water vapour conductance of the Sinai breed was 25% lower than predicted on the basis of egg mass.
4. The low permeability of the Sinai egg shell might be related to its higher than predicted thickness, which did not interfere with the shell functional pore area.
5. The low water vapour conductance of the Sinai egg shell may reflect adaptations to its dry habitat. 相似文献
2. Body weight gain, age at 50% egg production, mortality, hen‐day egg production and food conversion values showed significant improvement with proportionate increase in cage space per layer.
3. Egg weight gradually increased with age but shell thickness was influenced neither by age of the hen nor by stocking density.
4. Yolk index and colour were superior in the lowest stocking density (more cage space) group; other egg quality traits and egg weight were not influenced by stocking density.
5. The albumen index, internal quality unit, yolk index and yolk colour values increased with age. 相似文献
2. The parameters estimated for this equation are based on (a) egg weights in terms of percentage of seasonal mean egg weight, and (b) age as percentage of maximum age of the hen. Therefore, if the season's mean egg weight is known for any species, breed or strain, the increase in egg weight can be easily predicted for the whole season, or for any particular hen age. For early prediction, egg weight expressed as a percentage of initial egg weight can be used, although such prediction will be somewhat less accurate.
3. The use of egg weight as a percentage of seasonal mean egg weight, and age as a percentage of maximum age, was found to overcome the differences between strains, breeds and even species, by applying the same denominators for egg weights and periods of lay.
4. At each point of hen age (mean egg weight), the egg weight grades can be easily estimated by employing the computerised Burr's (1967) equation. These values showed excellent fit with extensive field data, provided that only normal eggs and those originating from a single flock and from no more than two weeks of collection are counted. 相似文献
2. The relevance of these measurements depends on an equivalence of the domestic fowl and the human photopic spectral sensitivity curves, because the latter (CIE) type of curve is the basis of photometric units.
3. A comparison of the data on domestic fowl spectral sensitivity and the CIE‐data, however, shows a serious discrepancy. For most purposes in poultry research, therefore, the lux‐meter is not an appropriate instrument.
4. A better way of presenting the relative luminance of a lamp for domestic fowl ('galluminance') is by multiplying the spectral power distribution of the lamp (Eλ)—as documented by the manufacturer— by the relative spectral sensitivity distribution of the domestic fowl (Gλ).
5. For this purpose we present the log Gλ data in relative units per 5 nm. 相似文献
2. Yolk weight is related to hen age and may be predicted using a linear-by-linear function, the coefficients of which are the same for Cobb and Ross breeders. Allometric functions may be used to predict albumen weight from yolk weight, and shell weight from the weight of the egg contents. Egg weight is given by the sum of the three components.
3. The proportion of yolk increased with advancing age whilst the proportions of albumen and shell decreased. However, at a given age, larger eggs contain proportionally more albumen. Eggs from Cobb hens had proportionately more albumen than Ross eggs towards the end of lay.
4. A stochastic population model verified that these functions accurately reflect the proportional changes in the egg components with advancing hen age and at a given age, over a range of egg weights. 相似文献