2. Deformation was not completely reversible due to crumbling at the points of contact with the force.
3. There are three components of non‐destructive deformation: (a) local deformation at the points of contact, (b) local surface crumbling and (c) deformation of the over‐all shell structure.
4. The latter two are uncontrolled, contributing to errors in the prediction of fracture force and depending on the non‐destructive force applied.
5. These effects should be considered in test selection and interpretation.
6. The optimum non‐destructive force was found to be 1 kg. 相似文献
2. Hens of the population with the high incidence of whitening appeared to be more fearful than hens of the population with the low incidence of whitening.
3. Brown colouration of the egg shell and the incidence and degree of shell whitening declined as the hens aged.
4. Brown colouration and egg shell whitening were most pronounced on the blunt ends of the eggs.
5. A large part of the variation in egg shell whitening was attributable to the individual (hen) component of variance.
6. Differences in egg shell whitening, between the two populations, were detectable throughout the 26 weeks of the experiment.
7. Oviposition intervals were similar for normal and coated eggs when birds were not exposed to disturbance.
8. Disturbance of hens increased oviposition intervals and the incidence and degree of shell whitening, to a similar extent, in both populations.
9. It is concluded that stress‐related egg retention is not the sole factor responsible for abnormal egg shell whitening. Shell whitening may occur as a consequence of the premature termination of shell pigmentation as well as a consequence of the retardation of oviposition which occurs when hens are disturbed. 相似文献
2. The response in shell thickness to ahemeral lighting was more rapid (2.2 d) than for egg weight (4.2 d).
3. Differences between genotypes were evident in both the speed and magnitude of response.
4. Overall, egg weight and shell thickness on the 28‐h cycle were 7% and 8% greater than on 24 h.
5. The allometric increase indicates that the increase in shell weight was on average 14% more than the increase in egg weight. 相似文献
2. Breeder hens fed ad libitum and subjected to either conventional or intermittent lighting ingested respectively, 25 g and 14 to 17 g more than hens restricted to 115 g/d.
3. Body weight was greater in hens fed ad libitum irrespective of the lighting pattern and of the amount of food intake.
4. Persistency of egg production was impaired by intermittent lighting.
5. Ad libitum feeding reduced egg fertility. The decrease was larger in breeder hens on intermittent lighting.
6. Hatchability was increased in hens submitted to the symmetrical lighting pattern (0.5L:3.5d).
7. Egg and chick weights were higher in hens fed ad libitum.
8. Shell index and shell breaking strength increased in restricted hens on the intermittent lighting pattern (0.5L:3.5d) × 6.
9. The best performance was obtained in restricted hens on the conventional lighting pattern. 相似文献
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 HC1‐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. 相似文献
2. When loading continued until shell failure the mean value of the force at failure, Pf, decreased as the loading rate decreased.
3. Among eggs from a given population the mean value of the product PfRa was related to log ê (dW/dt) in a linear manner, where Ra is the reciprocal of the average curvature of the shell at the point of application of the load.
4. When loading had been halted shortly before the expected time of failure, delayed failure was observed in more than a quarter of the eggs.
5. The more closely the load approximated to the expected load at failure, the shorter the delay in eggs showing delayed failure.
6. There is a risk of loss of eggs through delayed shell fracture if they are stored in stacks of trays that permit some of them to bear loads that are not large enough to cause immediate fracture but are nevertheless fairly large. 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 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. Higher rates of fertility and hatchability of Japanese quail eggs were observed from parents of 10 to 19 weeks of age, with peak fertility and hatchability at 14 and 12 weeks of age, respectively.
3. Sex ratios of 1:2 to 1:5 gave comparable fertility and hatchability results.
4. The hatching performance of quail eggs from cage and deep litter reared breeders was comparable.
5. Fertility and hatchability were directly proportional to the egg weight.
6. Quail egg shell colour, tints and blotches were found to influence hatching performance.
7. Storing quail eggs at 16 ± 2°C and 75 ± 5% relative humidity for more than 4 d reduced hatchability.
8. Hatchability of eggs stored at room temperature was improved if they were sealed in polyethylene bags.
9. Provision of light during the first 14 d of incubation resulted in a photo‐acceleration of about 3.2 h. 相似文献
2. Whole blood viscosity was more than twice as high, and plasma triglyc‐eride and haemoglobin concentrations were over 30% higher in fat line than in lean line females fed ad libitum or in restricted birds of both genotypes.
3. Mean cell haemoglobin concentration was higher and mean cell volume lower in fat compared with lean line females.
4. Food restriction was associated with lower plasma triglyceride concentrations, lower numbers of heterophils and monocytes and a lower heterophil‐lymphocyte ratio.
5. Fat line birds had a higher blood pCO2 and lower pH than lean line birds.
6. Thermal stress was associated in ad libitum‐fed birds with a rise in blood pH and a decrease in pCO2, and in restricted birds with a decline in blood pH and an increase in pCO2.
7. Blood creatine kinase activity increased in all groups under thermal stress. 相似文献
2. The volume of water taken up by eggs that had been sanitised was significantly (P < 0.001) greater than that taken up by the control eggs. The volume of water taken up by the sanitised eggs increased as the flock age increased, whereas water uptake was maximal for the control eggs at 42 weeks of age.
3. There was no correlation between water uptake values and shell thickness or egg weight for either the sanitised or control eggs.
4. Sanitised eggs tended to dominate the “poor cuticle quality” category at all flock ages, when a subjective assessment of cuticle quality was made using the stain Edicol Supra Pea Green.
5. Egg sanitising did not affect shell reflectance values, shell thickness or the percentage of cracked shells.
6. When flock age reached 49 weeks of age, the sanitising process significantly (P < 0.001) reduced hatchability. 相似文献
2. Shell deformation and shell thickness were plotted for each egg and the regression line was calculated. The difference between the observed shell deformation and that predicted by the regression line was calculated for each egg and this distance, with changed sign, was called the shell deformation index.
3. The force needed to separate the shell membranes from a 10 mm wide strip of the shell was determined by a tensile testing machine and was termed attachment strength.
4. The correlation between shell deformation index and attachment strength was highly significant (r=0.88, P<0.0005). Thus the shell membranes contribute to shell strength, probably by serving as a reinforcement of the crystalline part of the shell. 相似文献
2. In hens receiving a normal diet containing a calcium supplement in a powdery form Pi increased from 25 to 42 mg/1 during an entire shell formation cycle (from 10 to 22 h after oviposition of the previous egg), while in cockerels Pi decreased slightly during the night.
3. This increase in Pi in hens, was not related to cessation of feeding at the onset of darkness but was specifically connected with the beginning of shell secretion.
4. When hens received calcium as crushed sea‐shells separately from the diet, the nocturnal peak in Pi virtually disappeared and only a temporary increase of 4 mg/1 between 10 and 14 h after oviposition remained.
5. These results indicate that the beginning of shell secretion is always accompanied by an increase in Pi and that a separate presentation of dietary calcium reduces the bone mobilisation at night. 相似文献
2. Rocking embryo cultures during the first half of incubation enhanced embryo growth.
3. Embryos explanted into ‘surrogate’ eggshells of either other individuals or other species have been successfully ‘hatched’.
4. A normal chorioallantois is formed in these surrogate eggshells. This enables a functional albumen sac to form and eggshell resorption to be achieved.
5. Embryos grown in ‘surrogate’ eggshells are slightly smaller than controls but otherwise normal.
6. The technique provides opportunities for genetic engineering experiments. 相似文献
2. Ultracentrifuge experiments at 2.7 × 105 g gave values of s 20, W = (1.49 + 0.16C) × 10?13 s for the sedimentation coefficient and D20 w = (1.12 + 0.19c) × 10?6 cm2 s?1 for the diffusion coefficient, c being the protein concentration (g/100 ml).
3. According to the Svedberg equation, these imply a molecular weight of 12,470 daltons, assuming [v_bar] = 0.74 ml/g.
4. Using refractometer measurements of protein concentration it was found that E 1% 1cm (278 nm) = 5.57 at pH 7.8.
5. From the ultraviolet absorption spectrum of the protein in 0.1 N NaOH it was concluded that the molecule probably contains four tyrosine residues and no tryptophan.
6. On this basis a revised amino acid composition is given. 相似文献
2. Egg, yolk, albumen and shell plus membrane weights increased, whereas the egg shape, specific gravity and shell thickness decreased between 49 and 154 days of age.
3. Yolk, albumen and shell plus membrane comprised 32–59%, 53–57% and 7–80%, respectively of the total egg weight.
4. Regression between the quail's age and the characteristics of eggs were derived and correlation coefficients ranged from —0–42 to — 0–86. The albumen weight was more highly correlated with egg weight than yolk weight.
5. Relationships were also derived between egg shape and specific gravity, and egg shape and albumen weight.
6. It was concluded that the eggs’ characteristics were modified as the quails aged, and the best criterion of the shell's strength was the egg shape. 相似文献
2. The data conformed to a mixed model and adjustments were made for the fixed effects sex, hatch date and location. Adjustment improved the precision of the estimates by reducing the error variances significantly.
3. Rearing equal numbers of birds from each family at different locations made the interactions negligible.
4. Weight gain was greater if illumination intensity up to 35 d was less.
5. Females were not heavier on the 1st day but were heavier on the 14th and 35th days than males.
6. Variance components and genetic parameters were estimated. 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. Hens received an adequate conventional layers’ diet and the lighting pattern was conventional (17 L:7 D). Observations were made early (31 to 40 weeks) and late (62 to 68 weeks of age) in the laying period.
3. Eggs were classified by position in the clutch sequence and significant negative correlations were found between shell weights of early eggs in the sequence and plasma phosphate at the end of the dark period.
4. No significant trends were found in plasma total calcium.
5. No significant differences were found in bone compositions of birds producing consistently more or less than average shell weight during the laying period.
6. The negative correlations between plasma phosphate and shell weight are consistent with the observations of Sauveur and Mongin (1983) and show that impairment of shell deposition is associated with skeletal mobilisation as indicated by increase in plasma phosphate. This is consistent with the observations on bone composition and indicates that selection for shell quality will tend to select birds which are not dependent on excessive skeletal mobilisation during shell formation. 相似文献
2. Replacing groundnut oil cake (GNC) by Niger oil cake (NC) on an isonitrogenous basis, did not affect egg production, egg weight or the amount of food required per dozen eggs.
3. The percentage retention of nitrogen from diets containing 30% GNC or 30% NC was similar.
4. The ME value of NC used was 3025 kcal/kg.
5. It is concluded that NC can replace GNC in layers’ diets. 相似文献