T. C. Carter

The hen's egg: Estimation of shell superficial area and egg volume, using measurements of fresh egg weight and shell length and breadth alone or in combination

1. Shell superficial area (S, mm2) and volume (V, mm3) of an egg can be estimated from any one or a combination of the following measurements: fresh egg weight (W, g), shell length (L, mm) and maximum shell breadth (B, mm). 2. Estimation equations and their error standard deviations are given. 3. The random error of the estimate is smallest when estimation is based on L, B and W together: 0.4% for S and 0.6% for V. 4. Estimation of S based on L and B together has the advantage over that based on W alone that it is unnecessary to measure the egg soon after lay; the random error is the same (0.7%).

The hen's egg: Genetics of taints in eggs from hens fed on rapeseed meal

1. Fishy taints in eggs from hens fed on rapeseed meal, which have been reported to occur in brown‐shelled eggs of some hens with Rhode Island Red ancestry, occur also in white‐shelled eggs of some hens of a strain of Brown Leghorns. 2. Genetic tests have demonstrated that tainting in these circumstances is conditional on the presence in the hen, in the heterozygous or homozygous state, of an autosomal semi‐dominant mutant gene that has variable expression, depending on environmental factors (including the rate of ingestion of rapeseed meal). 3. No simple test for the presence of this gene, applicable to either sex, can be anticipated at present.

The hen's egg: factors affecting the shearing strength of shell material.

Synopsis Experiments are described from which it is concluded that 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; shearing force falls and the precision of its measurement rises as the radius of the plunger is reduced; shearing force is related linearly to shell thickness ; 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 ; there are differences between hens and between strains of hen in the magnitude of the intercept, but not in the slope of the regression; shearing force is affected also by the glossiness of the shell; 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, spe...

The hen's egg: some factors affecting deformation in statically loaded shells.

Synopsis Experiments are described from which it was established that when a hens egg shell is loaded statically with a load that does not cause fracture, deformation of the shell occurs almost entirely in the close vicinity of the points at which the load is applied; a small amount of deformation occurs over the shell as a whole; most of the variance of the deformation is associated with variation in RxRy/(Rx+Ry) T2 e for the loading points, where Rx and Ry are the radii of principal curvature and T2 e, the local effective thickness of the shell, is equal to the estimated local mean thickness of the mineral moiety; part of the residual variance is associated with variation in for polar and equatorial loading respectively, where B is the maximum breadth of the egg, L its length, X‘m the distance from the plane of maximum width to the broad pole and Te the mean effective thickness of the shell; a small part of the residual variance is associated with variation in pore density near the loading points; a sm...

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

Synopsis 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: 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; it varied linearly with the thickness of the shell; 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; 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); there were differences between hens ...

The hen's egg: Estimation of shell superficial area and egg volume from four shell measurements

Synopsis In research on egg shell strength it is often necessary to estimate the shells superficial area or the eggs volume without recourse to water displacement. Accurate methods are available but they entail making numerous measurements of the shell. Approximate methods that require only three measurements are available but suffer from two disadvantages; they entail measuring the distance from the plane of maximum breadth to a pole, which is difficult to do accurately, and they make no provision for variation in the degree of plumpness (marilynia) of the egg at levels between the plane of maximum breadth and the poles. A simple method is described that is free of these disadvantages. Four measurements are made: the length, L, and maximum breadth, B, of the egg and the distances, X 1 and L − X 2, by which the poles project into an annulus of radius R. Each of these is divided by L to give quotients 1, b, x 1, x 2 and r. A skewness parameter p is estimated by solving the equation and its value is inser...

Some factors affecting the incidence of cracks in hens' egg shells.

Synopsis Six blocks of data are analysed: British Egg Marketing Board (BEMB) data on second quality eggs‐in‐shell in packing station throughput; shell thickness and colour data on 1,440 eggs sampled in 4 packing stations; crack incidence data on 162,480 individually recorded eggs from a two‐strain experimental flock kept in battery cages; similar data on 34,611 eggs from another experimental flock; shell thickness, volume and shape data on 76 eggs from 19 pairs of hens, one of each pair with a high and one with a low shell‐crack record; and BEMB data on the prevalence of battery and deep‐litter husbandry. Conclusions reached are: Over the last decade there has been a rise in the incidence of packing‐station egg downgrading in the United Kingdom; it is assumed to have been due largely to a rise in the incidence of cracked shells. The rise in crack incidence was probably not due primarily to deterioration in shell strength associated with high production rates or white shell colour; such associations were l...

The hen's egg: Shell cracking at impact on a heavy, stiff body and factors that affect it

1. Eggs from hens of three strains were dropped on to a heavy, stiff, smooth, plane body with impact at the equator of the shell; the height of drop, hc, just sufficient to produce shell failure was measured and the corresponding impact velocity, vc, calculated. 2. A small but commercially important percentage of the well‐formed eggs of one strain cracked when hc was as low as 3–3 mm and vc 250 mm/s. 3. Characteristics of the egg found to affect hc and vc included the overall thickness of its shell, thickness of its weak inner shell layer and average shell curvature, all measured at the point of impact, and its weight; its age also had a small effect (additional to that mediated through loss of weight); so did the degree of shell ridging. 4. No effect of shell colour was found. 5. Shell damage was typically a single hair‐crack that ran either round the equator or towards a pole.

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

Synopsis 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 c...

The hen's egg: Relationship between shell thickness and the amount of organic matter in the shell

Synopsis Percentage weight loss on ashing was measured in 110 shell segments: 4 segments per shell—broad polar cap, narrow polar cap and two halves of the “barrel” —from 28 shells from 4 strains of chicken. The membranes had been removed, by hand, from each shell segment and shell thickness measured with a biconvex anvil micrometer. For each segment the function γ = T (1 + Wodm/Wmdo) was calculated, where T is the mean thickness, Wo the weight loss upon ashing, Wm the ash weight, d0 the density of the organic matter in the shell (assumed to be 1.0075 g/cm3) and dm the density of the mineral matter (2.386 g/cm3). Govariance analysis of the regression of T on T for each shell segment within each strain showed that the regression was linear, that the lines did not differ in slope, but that there were significant differences between the adjusted means for strains and for segments. This is interpreted as demonstrating that (a) the amount of organic matter in incremental shell is constant, estimated at 0.68 per...