The hen's egg: Density of egg shell and egg contents

One hundred eggs were used, from hens of seven widely differing strains: two commercial brown‐egg hybrids (one British, one American), two commercial white‐egg hybrids (one British, one Canadian), one broiler strain, one highly inbred strain of laboratory White Leghorns and one laboratory strain of Brown Leghorns. The volume occupied by the shell of each egg was estimated from its surface area—itself estimated by means of a three‐parameter model (Carter, 1968)— and its mean thickness, measured with an anvil micrometer. The volume occupied by the egg contents was estimated by subtracting the shell volume from the egg volume, which was also estimated by means of the three‐parameter model. Mean overall shell density (counting as “shell” all mineral matter and spaces between the outer surface of the mineral shell and a surface through the tips of the mammillae) was estimated, by regressing shell weight on shell volume, to be 2.241 ±0.004 g./cm.³; covariance analysis showed that the strains were homogeneous in this respect. Mean incremental shell density (i.e. the density of shell distal to the mammillary region) was estimated, by regressing shell weight per unit surface area on shell thickness, to be 2.386±0.004 g./cm.³; the strains were homogeneous in this respect too. The mean depth of the intermammillary spaces was estimated to be 19.9 μ. All the residual deviation from the common regression line can be attributed to measurement error. The estimated density of incremental shell is lower than that of calcite; the packing fraction of the crystals in the shell aggregate and/or the atoms in the crystals was estimated to be 92.8 per cent. The density of the egg contents (at the temperature of the bird) was estimated by regressing weight of contents on volume of contents; covariance analysis revealed significant differences between strains, one of the brown‐egg hybrids having the highest density of egg contents, 1.045 g/cm.³, and the laboratory Brown Leghorns the lowest, 1.033; both commercial white‐egg hybrid strains gave a value of 1.040 g./cm.³.     

Variation in some shell membrane characteristics over different parts of the same shell

The variation in shell membrane thickness (μ), membrane weight (mg./cm.2), membrane nitrogen (μg. N/cm.2) and packing index (μg./cm.2/μ) from the broad pole, excluding the air space, to the narrow pole of the same egg has been studied. The pattern of variation for a given characteristic was the same in different eggs from the same bird. Two thickness patterns were found. In Group I thickness decreased from the B collar to the equator, increased again to the G collar and then decreased sharply at the H cap. In Group II the increase from the equator to the G collar was replaced by a continued, but less‐marked, decrease. There was a high, positive correlation between weight and nitrogen, but the relationship between weight and thickness varied within and between eggs. All eggs showed a very similar pattern of packing index variation, decreasing from the B to about the C collar and then increasing to the H cap, the pattern being the same whether measurements were made on wet or dry membranes.     

Relationship between egg‐shell colour and two measurements of shell strength in the Vasca breed

1. Egg‐shell colour, egg specific gravity, shell thickness and egg weight were determined for 2080 eggs from three varieties of the Vasca, a Spanish brown‐egg‐laying hen.

2. Intermediate, positive and significant (P < 0·01) correlation coefficients were found between egg‐shell colour and specific gravity (0·25), or shell thickness (0·21). There was a very high (0·84), significant (P < 0·01) correlation between the measures of shell strength.

3. Shell thickness was accurately predicted with both specific gravity and egg weight as independent variables (determination coefficient 0·74); eggshell colour did not explain any further variation.

4. All traits showed considerable departure from normality in the form of negative kurtosis (shell colour and specific gravity), positive kurtosis (shell thickness and egg weight), negative skewness (shell thickness) or positive skewness (egg weight).

5. Egg‐shell colour, specific gravity and shell thickness were less in July, in old birds and in eggs laid in the morning. Differences in egg quality traits between the three varieties were not significant.

     

The effect of variation in egg numbers,body weight and egg weight upon shell thickness

It is expected that when birds consume a diet with a fixed calcium content variation in the rate of egg production, in body weight or in egg weight will lead to variation in calcium consumption. This analysis investigated whether, in a particular experiment, this also led to variation in egg shell thickness. Data from 67 birds over ten consecutive 28‐d periods were considered. Within birds and within periods it was found that the relationships between shell thickness and these production characters varied at different dietary calcium levels and in some cases the partial regression coefficients calculated were different in sign from those expected. However, only comparatively small amounts of variation in shell thickness could be ascribed to yariation in egg numbers, body weight or egg weight and, after regression, significant (P<0.001) differences still existed in shell thickness between birds. In this investigation there was little tendency for the egg shells to become thinner as the birds aged and hence the correlation coefficients between shell thickness and each of the three production characters due to common seasonal or ageing effects were small. The correlation between the angular transformation of the percentage cracked egg shells produced by each bird and its'mean shell thickness was — 0.357.     

The Hen's egg: Factors affecting the shearing strength of shell material

Experiments are described from which it is concluded that

1. the force required to shear egg shell material can be measured with high precision by pressing a narrow, flat‐ended plunger on to the shell;

2. shearing force falls and the precision of its measurement rises as the radius of the plunger is reduced;

3. shearing force is related linearly to shell thickness ;

4. the regression line of shearing force on shell thickness does not pass through the origin but has a substantial positive intercept on the thickness axis, at about a third of the mean thickness ;

5. there are differences between hens and between strains of hen in the magnitude of the intercept, but not in the slope of the regression;

6. shearing force is affected also by the glossiness of the shell;

7. shearing force was not significantly affected by stripped membrane thickness, number of mammillae per unit area of shell, shell organic content (standardised for shell thickness), shell curvature, shell colour, mottling score, translucent patch score, speckling score, age of the egg or age of the hen that laid it;

8. measured with a plunger of radius 165 μm, the mean shearing strength of incremental shell was 57 kg wt/mm² (3–7 ton/in²).

The findings suggest that the shearing strength of egg shells might be increased by direct selection and by selection for shell glossiness.     

Studies on egg shell strength,shell stiffness,shell quantity,egg size and shape

Physical properties which included shell stiffness, egg weight, width and length, shell weight and thickness, percentage shell, shell weight per unit area, shape index and roundness were studied in relation to maximum force and energy absorbed at failure in 2733 eggs produced by sixty SCWL pullets. Pooled‐egg, bird‐average and individual‐bird bases were used for correlation and regression analyses.

All physical properties in combination accounted for 61.9 and 88.2 per cent of the variation in force and 19.6 and 59.5 per cent of energy absorbed at failure in pooled‐egg and bird‐average analyses respectively. The non‐destructive measurements of shell stiffness, egg size and shape gave R ² values of 60.5 and 86.9 per cent with force and 16.2 and 55.0 per cent with energy in corresponding analyses.

Shell stiffness proved to be the most important predictor of force at failure. Analyses in which variation of shell stiffness was explained by other physical properties supported the conclusion based on theories of elasticity applied to shell structures that shell stiffness was largely an indirect measurement of egg shell quantity together with lesser effects of egg size and shape.

Bird‐to‐bird variation in relations between physical properties and shell strength was evident from individual bird analyses. Coefficients of determination from force at failure regressed on shell stiffness had a mean value of 0.455 with a standard deviation of 0.178 (n = 60).     

A stereological study on calculation of volume values regarding lumbosacral segments of quails

In the study, total segment, grey matter and white matter volume values of lumbosacral segment of spinal cord in quails (Coturnix coturnix japonica) were stereologically examined. Regardless of sex, six adult quails were used as material. After the materials were perfused, they were dissected and their spinal cords were uncovered. Tissue samples were taken from each lumbosacral segment of spinal cord. After the tissue fixation process, 6–7 sections having a 5‐µm thickness were separated in every 50th section as from the first section, where the tissue was seen, among tissue samples of each segment. These segments were stained with haematoxylin–eosin staining. They were photographed via a microscope. By using the Cavalieri's principle, the volume values of both the total segment, grey matter (GM) and white matter (WM) in each lumbosacral segment were separately calculated. All these calculations were performed by using SHTEREOM 1.5 program. As a result, total volume, grey matter and white matter volume values of lumbosacral segments and white matter/total volume, grey matter/total volume, and grey matter/white matter volume fractions were obtained.     

Breeding for late egg shell quality in the domestic hen

An experiment is reported, in which shell weight per unit surface area was measured for eggs laid by pedigreed pullets at 33, 54 and 65 weeks of age, using a Rhode Island Red strain and a White Leghorn strain. Specific gravity and albumen quality were also measured and records of individual egg production were available.

The heritability of “shell thickness “ (i.e. shell weight per unit surface area) in the Rhode Island Reds declined from 0.57 in the first period to 0.33 in the last period. The genetic correlation between thickness in the first period and thickness in the last period was 0.90. The relative selection efficiencies expected by basing selection on early shell thickness with the object of improving late shell thickness were greater than 1.0, indicating that early selection would be the best method of improving shell quality in this strain. In the Leghorn flock, estimates of the heritability of shell thickness were low (0.07 to 0.20) and variable. The genetic correlations between thickness measured in different periods were generally lower than for the Rhode Island Reds, and relative selection efficiencies varied widely. The Leghorns had much thicker shells than the Rhode Island Reds at all times of the year but showed little prospect of further improvement in shell thickness whichever time of measurement was used as a basis for selection.

Specific gravity was found to be highly genetically correlated with shell thickness and so would be a good estimator of shell thickness, although more eggs per pullet must be measured to give the same accuracy as direct measurement of shell weight per unit area. There were no adverse genetic correlations between thickness and the other traits measured, except perhaps in the case of albumen quality.

It is concluded that the lack of any general improvement in end‐of‐year shell strength is probably not due to low heritability, to adverse genetic correlations or to inaccurate methods of measuring shell thickness, but to a lack of selection pressure.     

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.     

The effect of fermented persimmon shell diet supplementation on the growth performance and blood parameters in finishing pigs

The objective of the present study was to investigate the effects of fermented persimmon shell diet (FPSD) supplementation on growth performance and blood parameters in 96 Berkshire pigs. The FPSD was made from persimmon shell and mixed with rice bran and barley bran. Samples of FPSD on day 0 (D0) and day 60 (D60) were analyzed for chemical composition, pH and organic acids. The experimental diets were 0, 3, 5 and 7% FPSD added to C, T1, T2 and T3 of finishing diets on fresh matter basis. Dry matter (DM) was lower (P < 0.01) and crude protein was higher (P < 0.01) on D60 than on D0. pH value decreased (P < 0.01) on D60 than on D0 but organic acids were increased (P < 0.01). Average daily gain was higher (P < 0.05) in T2 than in other groups. Average daily feed intake was higher (P < 0.05) in T2 than in other groups. Total cholesterol was higher (P < 0.05) in T3 than in other groups. High‐density lipoprotein cholesterol increased (P < 0.05) in groups by the addition of FPSD. Blood urea nitrogen was lower (P < 0.05) in C than in other groups. The results indicate that FPSD improved the growth performance and blood parameters in Berkshire pigs.     

The Hen's egg: Variation in tensile strength of shell material and its relationship with shearing strength

The tensile strength of egg‐shell material is believed to play an important role in determining whether or not a shell will crack when exposed to an environmental insult. Experiments are described in which shell tensile strength was measured. It is concluded that:

1. the force required to produce tensile failure did not vary linearly with the width of the piece of shell under test, but with its two‐thirds power;

2. it varied linearly with the thickness of the shell;

3. the line relating force at tensile failure to shell thickness did not pass through the origin but intercepted the thickness axis at between about 90 and 130 μm, indicating that the inner layers of a shell, up to about a third of its thickness, contributed little or nothing to its tensile strength;

4. the slope of the line did not vary with hen or strain of hen, indicating that the shells did not differ in the tensile strength of the material constituting their outer layers (i.e. about the outer two‐thirds);

5. there were differences between hens and strains in the magnitude of the intercept: shells of the same thickness but from different hens or strains differed in force at tensile failure;

6. the existence of between‐strain differences in intercept constitutes prima facie evidence that the variation in this trait is under genetic control;

7. there was a fairly large within‐egg residual component of the variance of force at tensile failure; it represents real variation in tensile strength between apparently similar pieces of the same shell and is believed to be an effect of chance in the distribution of flaws in the shell material;

8. for any one hen the intercept is the same as that found when shearing strength is measured, so shearing strength (which can be determined easily, quickly and precisely) can be used as a predictor of tensile strength.

Implications for poultry breeders are discussed; it is suggested that they should select for shell strength instead of shell thickness, measuring strength as shearing strength.     

The relationship between thickness and snapping strength in egg shells of the domestic fowl

Comparable pieces of egg shell from individual eggs of the domestic fowl were filed to give different thicknesses, they were then snapped and the relationship between snapping strength (S) and the square of the thickness (T ²) was studied.

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.     

A study of the progressive deposition of shell in the shell gland of the domestic hen

It is known that the organic matrix of the shell is not distributed evenly throughout the calcified portion and an experiment has been described in which incompletely shelled eggs were removed from a group of domestic hens after being in the shell gland for various known periods.

Rate of shell deposition and the timing of the deposition of the various layers in the shell has thus been determined, and it was found that shell deposition was initially slow for the first 3 h in the gland and thereafter more rapid, at a constant rate of 322 mg h^?1, until termination after 17 or 18 h. The narrow layer low in matrix at the top of the mammillary layer of the shell was laid down during the 7th to 9th hour in the gland and did not appear to be associated with any change in shell deposition rate. It was also found that the characteristic pole to pole thickness patterns of shells were present at the earliest measurable stage, that is after about 8 h in the gland.     

The application of shell strength measurements in egg shell quality determination

Comparisons of shell thickness, specific gravity and shell strength (breaking strength and shell deformation under load) for individual loads have been made and correlation coefficients determined. The relationship between egg size, shell strength and shell deformation have been investigated.

Shell strength has been correlated with shell thickness and specific gravity, but due to the complex nature of shell strength, it has been concluded that for routine work the measurement of shell thickness either indirectly or by specific gravity or by direct shell thickness measurement gives the most practical indication of shell quality.     

The hen's egg: Relationships of seven characteristics of the strain of hen to the incidence of cracks and other shell defects

1. Multiple regression and path‐coefficient analysis show that the factors with greatest influence on the incidence of cracks and other shell defects in three random‐sample tests of 47 entries of 28 strains were, in descending order, mean shell colour, mean shell thickness, mean egg production and mean egg weight, and that median age at maturity, mean body weight at 140 d and mean weight increase between 140 and 500 d had no effect.

2. Breeders who wish to exercise indirect selection for low crack incidence should consider selecting for dark shell colour rather than high shell thickness.     

The hen's egg: Evidence on the mechanism relating shell strength to loading rate

1. The decrease in strength of an egg shell which is known to accompany an increase in the period of time over which a load is applied might come about by either of two mechanisms: a decrease in the strength of the material constituting the strong, outer layer of the mineral shell, or a decrease in the thickness of this layer brought about by deepening of the crevices that are normally present between adjacent crystal columns in the weak, inner layer of the shell.

2. Experiments designed to discriminate between these mechanisms are described: the results indicate the second mechanism.

3. This mechanism offers explanations for various other shell phenomena, including delayed fracture under a static, cyclical or recurrent load.

4. The main implication for the poultry industry is that any external insult to a shell is likely to weaken it by doing damage that is local, internal, irreparable and cumulative, even though it may be invisible from the outside.     

The hen's egg: Shell shape and size parameters and their interrelations

The occurrence of a crack in an egg shell depends in part on the local strength of the shell, which in turn depends on its curvatures as well as its thickness, and therefore on its shape. Selection for shell shape is therefore needed; but before the breeder can do this he must have a rapid and accurate method of quantifying shell shape, and knowledge of the factors that affect its variation.

A procedure is described whereby nine measurements of an egg shell—length, maximum breadth, distance from the plane of maximum breadth to the broad pole and the distances by which each pole projects into annuli of diameters 1.5, 2.5 and 3.5 cm—are used to obtain an equation describing the profile of the egg in polar coordinates. It has five parameters that measure, independently, five shell characteristics: scale, aspect (breadth‐to‐length ratio), skewness, marilynia (concordant bulging between the poles and the plane of maximum breadth) and platycephaly (discordant bulging). Egg volume and superficial area can be obtained by integration, shell curvatures by differentiation. An experiment in which the computed volumes of 61 eggs from 19 hens of four strains were compared with the volumes measured by water displacement failed to detect, in single‐yolked eggs, any discrepancy not attributable to random measurement error, which was 0–2 per cent of mean egg volume.

Aspect, marilynia and platycephaly are shown to be correlated inter se and with egg size; differences between hens and strains in respect of them are shown to exist. Making the shell measurements could be automated and use of the method could lead to improved efficiency of selection for egg size as well as shape.     

Anatomical Studies on the Spinal Cord Segments of the Impala

The anatomy of the spinal cord segments was studied and recorded for the impala. The root attachment lengths were greatest at C₃, T₁₀ and L₃ cord segment levels in the respective regions. As to the root emergence length the greatest lengths were observed at C7, T_]0> L5 and S₁ cord segment levels respectively. The interroot interval was longest at C₂, T₈ and L₁ segments respectively. The longest cord segments were C2, T13, L₂ and S₂ segments. The widest cord segments of their respective regions were C₇, T₁, L5 and S₁ cord segments. As to segment volume C3, T₁₃, L₂ and S₁ were the most voluminous cord segments in the respective cord regions. Statistical analysis revealed a high correlation among all of the study parameters suggesting a high degree of multicolinearity. Gross anatomical relationships concerning the location of the spinal cord segments with respect to the vertebrae were studied. The cord segments C], T_s–T₄ and Li–L₃ were within their vertebral limits. In the impala the spinal cord terminated at the midlevel of S₄ vertebra.     

Fiber digestion in various segments of the hindgut of horses fed grass hay or silage

We studied in vivo fiber digestibility and fermentation parameters such as volatile fatty acid concentration and in vitro degradation in each segment of hindgut of horses fed timothy hay or silage made from the same sward. Six Thoroughbred horses were fed timothy hay or silage in equal amounts (1.6% of bodyweight per day, bodyweight mean 572 kg) every 3 h per day, then slaughtered. There were no differences between hay and silage in the concentration of the total volatile fatty acids, the apparent digestibility of dry matter, organic matter, and fiber, and in vitro neutral detergent fiber (NDF) disappearance rate in each segment. The total volatile fatty acid concentration and the apparent digestibility of dry and organic matter and fiber differed ( P  < 0.01) depending on the digestive segments. Both for hay and silage, the concentration of total volatile fatty acids in the digesta liquid phase largely increased ( P  < 0.01) from the cecum to the right ventral colon, and kept a constant value from the right ventral colon to the right dorsal colon, and then decreased from the right dorsal colon to the small colon. For dry and organic matter and fiber components, the apparent digestibility changed in the same manner from former to hinder segments of the hindgut. Regardless of diet, dry and organic matter and fiber components showed lower values in the cecum and the right ventral colon and increased ( P  < 0.01) largely from the right ventral colon to the left dorsal colon, then kept constant values in segments to the rear of left dorsal colon. There were no differences in in vitro NDF disappearance among cecum, ventral colon and dorsal colon.