The relationship between thickness and snapping strength in egg shells

The relationship between snapping strength and thickness was studied by filing away part of the egg shell in order to produce varying thicknesses. Thick shells of the ostrich, rhea and emu were used, because it was necessary to establish whether the new approach was worth while, before studying the thinner egg shells of the domestic hen which technically present a much more difficult problem.

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.     

Presence and incidence of food-borne pathogens in Australian chicken litter

1.?Litter samples were collected at the end of the production cycle from spread litter in a single shed from each of 28 farms distributed across the three Eastern seaboard States of Australia.

2.?The geometric mean for Salmonella was 44 Most Probable Number (MPN)/g for the 20 positive samples. Five samples were between 100 and 1000 MPN/g and one at 10⁵ MPN/g, indicating a range of factors are contributing to these varying loads of this organism in litter.

3.?The geometric mean for Campylobacter was 30 MPN/g for the 10 positive samples, with 7 of these samples being <100 MPN/g. The low prevalence and incidence of Campylobacter were possibly due to the rapid die-off of this organism.

4.?E. coli values were markedly higher than the two key pathogens (geometric mean 2?0 × 10⁵ colony forming units (cfu)/g) with overall values being more or less within the same range across all samples in the trial, suggesting a uniform contribution pattern of these organisms in litter.

5.?Listeria monocytogenes was absent in all samples and this organism appears not to be an issue in litter.

6.?The dominant (70% of the isolates) Salmonella serovar was S. Sofia (a common serovar isolated from chickens in Australia) and was isolated across all regions. Other major serovars were S. Virchow and S. Chester (at 10%) and S. Bovismorbificans and S. Infantis (at 8%) with these serovars demonstrating a spatial distribution across the major regions tested.

7.?There is potential to re-use litter in the environment depending on end use and the support of relevant application practices and guidelines.     

Effect of cuticle removal on the water vapour conductance of egg shells of several species of domestic bird

1. The effect of egg shell cuticle removal, using a 14.7 mM solution of sodium hypochlorite, on the water vapour conductance of egg shells was studied in 5 species of domestic bird.

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.     

Thermal panting and respiratory alkalosis in the laying hen

1. Changes in respiratory rate (f), rectal temperature (T_r ) and blood acid‐base values were measured in laying hens exposed to ambient temperatures (T_a) of 32, 35, 38 or 41 °G.

2. At T_a 32 °G there was no panting. At T_a 35 °G panting occurred without any increase in T_r but there was a slight alkalosis (pH 7.55).

3. At T_a 38 °G T_r increased and panting was accompanied by moderate alkalosis (pH 7.58).

4. At T_a 41 °G T_r increased considerably and severe alkalosis developed (pH 7.65).

5. From the relation between T_r , f and pH it is concluded that some degree of alkalosis is a normal response to panting in the laying hen.     

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%).     

Thermoneutral zone and resting metabolic rate of growing white leghorn‐type chickens

1. Metabolic rate was determined once a week in pullets from commercial flocks of the local White Leghorn strain from the age of 1 d to 13 weeks.

2. The equations relating minimal resting metabolic rate and body weight were: for body weights of 40 to 163 g Y ‐ 1–83 W ^0.986, and for 163 to 1 200 g Y = 11.64 W ^0.623, where Y = O₂ consumption (ml/bird h) and W = body weight (g).

3. The relationship between lower critical temperature (T_d) and age may be described by two equations: for pullets of 1 to 21 d of age Y = 35 ‐ 0.286 X, and for 21 to 70 d of age Y = 63.3 X^{‐ 0.254}, where Y = T _d(°C) and X = age (d).

4. T_d related to body weight is also described by two equations: for body weights of 40 to 163 g Y = ’42 ‐ 1.18 W^0.480 , and for 163 to 800 g r = 42 ‐ 3.60 W^0.260

5. These equations could be used to calculate the T_d on a day‐to‐day basis related to age or body weight.     

Structural flaws in some very strong egg shells

Egg shells from a particular bird gave very high values for strength at the broad pole when tested by an impact method.

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.     

Thermoneutral zone and resting metabolic rate of broilers

1. Metabolic rate was determined once a week in broilers from a commercial source, from 1 to 63 d of age.

2. The equations relating minimal resting metabolic rate (oxygen consumption, ml/bird h,y) and body weight (W) were: males 45 to 497 g, y = 3.2 W^0.882 597 to 3000 g, y = 40.5 W^0.483; females 45 to 514 g, y = 2.52 W^0.881; 514 to 2500 g,y = 12.3 W^0.627.

3. The relationship between lower critical temperature (T_cl , °C,y) and age (d, x) may be described by the following equations: chicks 1 to 21 d, y = 34.2 ‐ 0.32 x; 14 to 63 d,y = 49.4 × ^?0194.

4. The relationship between T_cl and W may be described by one equation for both sexes between 100 and 3000 g, y = 62.15 W^?0.135..

5. The equations for T_cl and data for upper critical temperature (T_cu ) could be used to obtain maximal performance from broilers, with reduced costs, by providing a suitable environment related to age or body weight.     

Changes in polymorphic gene frequencies in strains of chickens selected for resistance to Marek's disease

1. Resistance to Marek's disease (MD) was selected over five generations in three strains and their four substrains.

2. MD mortality decreased consistently on natural exposure, but in birds artificially inoculated the mortality increased again in later generations.

3. Changes of gene frequencies at five polymorphic loci—blood group A, B and D, plasma esterase and alkaline phosphatase loci—were examined.

4. The frequencies of blood group A⁶ and B⁸ alleles showed a consistent trend of increase and the B ¹¹ allele gradually decreased in most strains. The Akp allele of alkaline phosphatase increased significantly in two of seven strains.

5. Comparisons of homozygotes and heterozygotes revealed a significant difference only at the A locus.     

Effects of short intermittent lighting on food consumption and performance of dwarf broiler breeders and progeny

1. Two hundred and sixty four dwarf broiler breeder hens were subjected to ad libitum or restricted feeding and to four lighting patterns: 15L (bright light):9D (dark), 15L:9d (dim light), 2L:10d: 1L:11d, (0.5L:3.5d) × 6.

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.     

The action of sulphanilamide on shell deposition

1. The action of sulphanilamide on egg shell deposition has been studied in the domestic fowl. The length of time that eggs remain in the shell gland was measured; the relative thickness and protoporphyrin pigment concentration for egg shells removed from the shell gland were determined; egg shell structure was examined using a replica technique.

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.     

A 31P topical magnetic resonance study of embryonic development in hens' eggs

1. A ³¹P topical magnetic resonance study of whole chicken's eggs in vivo is described.

2. Resonances from adenosine triphosphate, phosphocreatine, inorganic phosphate and phosphorous storage protein were observed. These changed in relative intensity as the embryo developed.

3. No ill effects due to exposure to radiofrequency radiation or magnetic fields were observed.

4. It is concluded that topical magnetic resonance can make a useful contribution to the study of embryonic development in avian eggs.     

Effect of spray sanitising on hatching egg cuticle efficacy and hatchability

1. Eggs from a broiler breeder flock were sanitised using a continuous spray sanitising machine. The effect of this treatment on the ability of the cuticle to resist water and bacterial penetration was investigated throughout the production cycle.

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.     

The strength of guinea fowl (Numida meleagris) egg shells

The strength of guinea fowl egg shells has been studied by piercing and snapping methods and the results were compared with those from the domestic hen.

Guinea fowl egg shells are stronger and thicker than egg shells from the domestic hen and the shells are stronger even after allowing for their greater thickness. The difference in snapping strength between shells of the two species is far greater when the shells are snapped inwards than when they are snapped outwards. Studies of the crystal structure, histological structure and chemical analysis revealed interesting differences between the two types of shell but it was not possible to say which of these differences accounted for the differences in strength.     

Effects of food intake regulation on the energy metabolism of laying hens

1. The effects of dietary energy restriction on the energy metabolism of post‐peak‐of‐lay hens of two hybrid layer strains were studied by indirect calorimetry.

2. Starving and resting rates of heat production (SHP and RHP) were measured, over 1‐d periods, at intervals during a 25‐week period in which the experimental birds were individually restricted to 80% of their previous energy intake ad libitum.

3. In both strains mean RHP per bird was about 7% lower in the restricted birds than in controls fed ad libitum, but when RHP was expressed in terms of metabolic body size (kg^0.75) the two groups did not differ.

4. Mean SHP per bird was about 18% lower in the restricted birds of both strains than in the corresponding controls; the decrease in SHP per kg^0.75 was 12%.

5. Heat increment of feeding and calculated maintenance energy were higher, and net availability of metabolisable energy for maintenance and production was lower, in the restricted than in the control groups.

6. Gross efficiencies of egg production, in terms of both mass and energy, increased in the restricted birds.

7. Live‐weight and total carcass energy after 25 weeks of restriction were respectively about 15% and 30% lower in the restricted groups of both strains than in the groups fed ad libitum.     

Thyroid function in relation to trimethylamine oxidation in immature domestic fowl fed on rapeseed meal

1. Two groups of 12‐week‐old female chicks were selected for their ability to oxidise ¹⁴C‐trimethylamine (TMA) after being fed on a diet containing 100 g high‐glucosinolate rapeseed meal (RSM)/kg for 14 d. A third group (control) was fed on a rapeseed‐free diet. Measurements of thyroid activity and hepatic TMA oxidase activity were made after a further week on the diets.

2. After feeding RSM, hepatic TMA oxidase was very low (P < 0–001) in one group (sensitive) but was unaffected in the other group (resistant). Thyroid size was increased in both groups receiving RSM but was larger (P<0–001) in sensitive birds.

3. Plasma half life of thyroxine (T₄) and its metabolic clearance rate were not affected by feeding RSM; thyroidal secretion was reduced (P < 0–05) to the same extent in both groups.

4. Plasma concentration of triiodothyronine was decreased in both groups after feeding RSM (P<0–05); plasma T₄ concentration was increased (P<0–05) only in sensitive birds.

5. The results indicate that the short‐term depression of TMA oxidation in birds sensitive to RSM is not mediated by the thyroid.     

Molecular weight and amino acid composition of fowl delta‐globulin

1. The molecular weight of delta‐globulin was estimated chromato‐graphically to be about 10,700 daltons.

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 D_{20 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.     

Behaviour of egg shell under compression in relation to deformation measurements1

1. The egg does not completely obey Hook's law when compressed between flat surfaces.

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.     

A note on microbial growth on hen egg‐shells

1. Two strains of cuticle‐digesting pseudomonads were isolated from the surface of hens’ egg‐shells that had been stored in a humid atmosphere at 25 °C. Digestion was due to a protease, the demonstration of which was only achieved in media containing cuticle.

2. The egg‐shells were colonised by yeasts also, but the growth of these organisms appeared to be dependent upon the pseudomonads for the release of nutrients from the cuticle.

3. The pseudomonads would not grow on cuticle in situ unless the relative humidity was about 100%.     

Studies of membrane,mammilary cores and cuticle of the hen egg shell

Mammillary cores and outer shell membrane have been studied by comparing the weight and chemical composition of outer membrane with cores still attached and of outer membrane free from cores, from the same shells. Inner membrane and cuticle have also been investigated.

The weights of inner and outer membrane are significantly correlated (P < 0.05). Both membranes contain galactosamine, glucosamine, sialic acid, glucose, mannose and fucose but in different proportions. Uronic acid is probably absent.

An average of 3.3 mg of organic mammillary core material per shell (52 μg/cm²) was present in the shells investigated, but there was a trend suggesting that eggs laid by more mature hens may contain rather more. Cores are rich in hexo‐samine, sialic acid and hexose, but the probable absence of uronic acid suggests that chondroitin sulphates play no part in shell initiation. There were no major differences in the amino acid spectrum of membrane samples with and without cores.

Galactosamine, glucosamine, sialic acid, galactose, glucose, mannose, fucose and an unidentified pentose are present in the cuticle. In some respects these sugars are combined differently from their combination in the adjacent outer levels of the matrix.