The influence of the cuticle on egg‐shell strength

1. Sixty sound eggs, assumed to have shell cuticle, were paired according to egg‐shell deformation value.

2. Egg weight and shell quality characteristics were recorded for the eggs and the cuticle was then removed from one egg of each pair.

3. Egg weight and shell quality were re‐assessed for the eggs from which the cuticle had been removed.

4. The cuticle made a significant (P<0.01) contribution to shell thickness and removal of it appeared to reduce shell strength when measured directly, but the method of measurement was too variable to establish this with statistical significance.     

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%.     

A note on changes in egg‐shell porosity with flock age and season during the first breeding cycle of domestic ducks

1. — Changes in egg weight and egg‐shell porosity with flock age and season are presented for domestic duck flocks in their first laying cycle.

2. — The first eggs laid are of low weight and shell porosity but generally by the fifth week of lay both characteristics have increased to the values found in the mature flock.

3. —For mature flocks porosity decreases in the summer and the consequences of this are considered in relation to the observed decrease in hatch‐ability at this time.     

A note on the shelf‐life and spoilage of commercially‐processed chicken giblets

1. When chicken giblet tissues wrapped individually in polythene were stored at 1 °C, “ off” odours were detected in 11 to 14 d with necks (mean 12.3 d) tending to spoil before gizzards, hearts and livers (means 13.0 to 13.7 d).

2. In all cases, the predominant organisms at spoilage were Pseudo‐monas spp. with lower numbers of Acinetobacter spp.

3. Chlorination of process water at about 50 mg total residual chlorine/1 (including 0.1 to 0.9 mg free chlorine/1) extended the shelf‐life of giblets held at 1 °C by up to 3 d, and prior freezing of these tissues gave an extension of 1 to 2 d but combining the two treatments did not have an additive effect.

4. Immersing giblets for 1 min in a solution containing 100 g potassium sorbate/1 (pH 8.0) doubled the shelf‐life of each type of tissue by retarding growth of the normal spoilage microflora.     

Effects of lauryl sulphate on egg‐shell quality in laying hens

1. The effect of feeding the detergent, sodium lauryl sulphate at concentrations up to 10 g/kg diet on egg‐shell quality was examined in laying hens at 24, 36 and 48 weeks of age.

2. Lauryl sulphate at 2.5 g/kg or more in the diet significantly increased shell breaking strength, shell thickness and shell weight at 24 and 36 weeks. In 48‐week‐old hens only shell breaking strength was increased significantly. Egg production and egg weight were not affected significantly by lauryl sulphate.

3. Lauryl sulphate might increase these measures of quality by increasing shell deposition and/or shell elasticity.     

Effect of light,vitamin d and dietary phosphorus on egg‐shell quality late in the pullet laying year

1. Eighteen diets supplying all combinations of three phosphorus contents (3.1, 4.0 and 4.8 g non‐phytate P/kg) and six vitamin D supplements (37.5 or 150 μg cholecalciferol/kg; or 16 or 24 μg 25‐hydroxy‐cholecalciferol/kg; or 37.5 μg cholecalciferol/kg with either 16 or 24 μg 25‐hydroxycholecalciferol/kg) were fed to 2 880 pullets of two stocks from 64 to 74 weeks of age. The birds were housed in eight light‐proof rooms, four of which had 24‐h light‐dark cycles (16L : 8D) and four had 28‐h cycles (20L : 8D).

2. The dietary treatments had no significant effect upon food intake, egg output, shell thickness, shell deformation or specific gravity of the eggs.

3. The 28‐h cycle reduced mean rate of lay by 4.5%, increased egg weight by 5.8% and increased shell thickness by 9.4%. The proportion of eggs with shell faults revealed on candling was reduced from 4.1 % to 2.8%.

4. It is concluded from this and other sources that decreasing dietary phosphorus or modifying vitamin D supplements may sometimes lead to increases in shell thickness of the order of 1 to 2%, but that these changes are unlikely to result in a measurable reduction in the proportion of cracked eggs late in the laying year.

5. A 28‐h light‐dark cycle results in a longer and more uniform interval between consecutive ovipositions and thus gives reliable increases in shell thickness which are large enough to reduce the proportion of cracked eggs in many practical situations. Whether it is profitable to use an ahemeral cycle will depend upon the relative prices paid for eggs of different sizes.     

The use of the plasma chemistry unit as an aid to the scanning electron microscope study of avian egg‐shell structure

1. In order to study the mammillary layer of the avian egg shell by scanning electron microscopy, it is necessary to separate the outer shell membrane from the calcified shell.

2. Chemical methods of effecting membrane removal are difficult to standardise due to variations in the strength of the membrane‐shell bond.

3. The use of reactive gas plasma provides an alternative, more efficient method for removing membranes without the risk of damage to underlying crystalline structures.     

A note on the population structure of the Avileña breed of cattle in Spain

The objective of this study was to describe the population structure of the Avileña breed considering the flow of genes between herds, effective number of herds and generation intervals. Characteristics of the breed which modify either the increase of level of inbreeding or the hierarchical structure of the population were also considered.     

Studies on the avian shell gland during egg formation: The effect of acetazol‐amide on the transfer of ions to the albumen 1

1. Twenty‐five laying hens were fed on a diet containing 100 mg acetazolamide/kg in order to determine the effects of a decrease in the activity of carbonic anhydrase on the transfer of minerals to the egg albumen.

2. Treatment with acetazolamide decreased the rate of shell formation by 44%; reduced the concentrations of water and Na+ in the albumen at the beginning of the plumping stage but increased the accumulation of water during plumping; increased the concentration of Cl‐ in the albumen after the 6‐h stage without any appreciable change in K+ and Ca²⁺ concentrations.

3. The computed relationships between the concentrations of different ions also showed that the transfer of water and Na+ were linked during egg formation, that a water‐independent, acetazolamide‐sensitive reabsorption of Na+ occurred after the 10‐h stage and that Na+ and Cl‐moved simultaneously up to 14 h but with the ratio of Cl‐ to Na+ three times higher in the treated group.

4. It is concluded that acetazolamide impairs the transfer of Na+ and Cl‐ between the albumen and the extracellular fluid and that secretion of Ca²⁺ into the uterine lumen seems to depend on Na+ and Cl‐ reabsorption.     

Factors affecting the non‐destructive and destructive methods of measuring egg shell strength by the quasi‐static compression test1

1. Precise measurements of shell deformation and fracture force were made to examine the destructive and non‐destructive quasi‐static compression tests of egg shell strength.

2. Prediction of shell strength from shell deformation (d) was not greatly improved by combining egg length, diameter and shell thickness with shell deformation. At the equator 54% of the variation in fracture force (F) was accounted for by an equation F = 8467 ‐ 115630i+584166d² compared with 57% when 13 measured and generated parameters were included (singly and in combination) in the analysis.

3. Cracks changed the deformation by an average of 8% providing the crack was not near the points where force was applied. Cracked eggs could be tested to reduce the bias introduced by eliminating such eggs from experiments. Empirical factors must, however, be established to correct such deformation readings.

4. Use of a hole or rubber on the lower compression surface to stabilise the egg increased the force required to fracture the shell at the upper flat surface Such surfaces are undesirable because the fracture site is biased towards the upper contact point when force is distributed at the lower surface. Shell deformation and its correlation with strength was also reduced.

5. The fracture force predicted by a non‐destructive deformation measurement was greatly affected by the force applied. The optimum test force was 1 kg at the equator.     

A comparison of the effects of two low‐calcium diets on egg production in the domestic fowl

1. Hens fed on a diet containing 0–05% calcium virtually ceased egg laying (production <4%) whereas those fed on a diet containing 0–5% Ca maintained production at between 20 and 30%.

2. After a return to a normal diet (3% Ca) egg weight, shell weight, ovarian characteristics and oviduct size were of a similar nature in the two groups, though the differences in egg weight, shell weight and shell calcium were significant at the 1 % level.

3. Bone weight and bone ash did not differ significantly between the groups but after a return to normal rations, bone weight and bone ash became higher in the group that had received the 0.05% Ca diet.

4. There were no clinical signs of bone demineralisation during the experiments.     

Effect of gradual acclimation to high ambient temperatures on egg‐shell quality of the Sinai Bedouin fowl,the commercial white leghorn and their crossbreds

1. The effect of gradual acclimation to high ambient temperatures on egg‐shell quality was studied in the Sinai fowl, the commercial White Leghorn, and their reciprocal crossbreds.

2. The Leghorn egg was characterised by a thinner and weaker shell compared with the Sinai and the crossbreds, at all the experimental temperatures.

3. In contrast to other reports, high ambient temperatures for a long period had only mild effects on egg‐shell quality.

4. The results suggest that gradual acclimation to high ambient temperatures might improve the efficiency of the physiological mechanisms involved in the hen's response to heat. Consequently, the reproductive process adapts to the hot environmental conditions.

5. The results indicate that the Sinai breed might be used for future selection of a breed, highly resistant to extreme environmental conditions and with an improved shell quality.     

Plasma inorganic phosphorus concentration during egg‐shell formation: Effect of the physical form of the dietary calcium

1. Four experiments were carried out with Warren laying hens to elucidate the changes in plasma inorganic phosphorus (P_i) concentration during egg formation.

2. In hens receiving a normal diet containing a calcium supplement in a powdery form P_i 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 P_i decreased slightly during the night.

3. This increase in P_i 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.     

Choice feeding of the egg‐type pullet

1. Egg‐type pullets from 43 to 127 d of age were fed either a high‐protein concentrate (493 g/kg), a protein concentrate (323 g/kg) or a grower diet, together with either whole wheat or whole barley. Further birds received a complete diet and had no choice.

2. Eighty‐four point six, 69.5 and 31.4% respectively of the food consumed by the birds which received the high‐protein concentrate, protein concentrate or grower diet with wheat consisted of the whole cereal. The corresponding figures for the birds which received barley were 73.9, 41.3 and 10.9% respectively.

3. There were no significant differences in rate of food intake or growth between choice‐fed birds receiving whole wheat and the complete diet‐fed birds with no choice.     

Day‐length during rearing and the subsequent egg production of meat‐strain pullets

1. The effects of lighting pattern on production to 399 d in caged, female, meat‐strain chickens was investigated. Energy intake was controlled from 56 to 399 d.

2. Four different rearing treatments with a subsequent constant 16‐h photoperiod during laying were used.

3. A 15‐h rearing photoperiod resulted in delayed sexual maturity, increased mature body weight and decreases in both total egg numbers and the proportion of smaller eggs, compared with a 6‐h photoperiod.

4. Continuous light to 56 d, although associated with a high incidence of subsequent blindness, resulted in satisfactory egg production.

5. Abrupt reduction in the photoperiod from 15 to 6 h for the 112 to 167 d period resulted in unsatisfactory subsequent performance, especially when the day‐length was only slowly increased to 16 h during laying.

6. In the two laying treatments, in which the photoperiod was increased gradually from 6 to 16 h during the 168 to 238‐d period, a decrease in the number of smaller eggs occurred, compared with the treatments in which a single abrupt increase in photoperiod was used.     

Effect of turning upon the sub‐embryonic fluid and albumen of the egg of the Japanese quail

1. The effects of egg turning upon the formation of sub‐embryonic fluid (SEF), and albumen weight and composition are described up to day 8 of incubation.

2. The density of albumen increased, and the density of yolk sac contents decreased, during the first 5 d of incubation. Failure to turn eggs diminished these changes.

3. The rate of formation of SEF and its maximum weight were lower if eggs were not turned, as was the rate of decrease in albumen weight.

4. The concentration of sodium and chloride, as well as osmolality, were higher in SEF than in thin albumen, and were affected by a failure to turn eggs.

5. Static incubation altered the concentrations of yolk nutrients in SEF.

6. It is concluded that the formation of SEF is primarily dependent upon the transfer of sodium and chloride from albumen to SEF so creating an osmotic force for water movement in the same direction. Turning the eggs promotes this process by ensuring an adequate supply of ions in thin albumen adjacent to the blastoderm.     

Differences in egg‐shell quality among the Sinai Bedouin fowl,the commercial white leghorn and their crossbreds

1. A comparison of egg‐shell characteristics was made among the Sinai breed (a desert inhabiting strain), the commercial White Leghorn and their reciprocal crossbreds.

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.     

The effect of 6‐ and 8‐hour light‐dark cycles on egg production and pattern of ovipositions

1. Two flocks of 60 laying hens were transferred from 14 h light (L): 10 h dark (D), to repeated 3L:3Dor4L:4D lighting schedules at 37 weeks of age. Egg production decreased slightly but egg weight and shell quality improved.

2. The intake of low‐calcium diet and of oyster shell were similar for each light period of each lighting regimen.

3. Ovipositions were distributed virtually at random throughout the day and the mean interval between successive eggs within a clutch was increased.

4. Reducing the total daily photoperiod from 12 to 6 h decreased daily food consumption.     

Genetic parameters of egg production,body weight and egg size in the red‐legged partridge

1. Heritability estimates of egg production, egg weight and body weight of red‐legged partridge were obtained.

2. Data from a population selected for increased egg production over four generations as well as from a random‐bred control population were available.

3. Heritability of egg number during the first production period was considerably higher than estimates for a second production period, induced by appropriate lighting.

4. Egg weight and body weight were highly heritable.     

Relationship between the shell membrane‐shell bond and shell deformation in hens’ eggs

1. The influence of the shell membranes on shell strength was studied in 21 Single Comb White Leghorn eggs.

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.