Influence of sequence length on the response to ahemeral lighting late in lay

1. An experiment is described in which 96 individually‐caged SCWL hens in two rooms were used to investigate the response to changing to a 28‐h cycle using a reverse treatment design.

2. The application of the 28‐h cycle did not affect mean rate of lay but increased mean egg weight and egg output.

3. Grouping the birds according to their preliminary sequence length yielded an interesting outcome. In both rooms, birds with short sequences (≤ 6 eggs) produced significantly more eggs under the 28‐h cycle, while those with long sequences (> 6 eggs) produced marginally fewer eggs. The same trend was also evident with egg output.

4. Changing from 24‐h to 28‐h increased yolk and albumen weights as well as shell quality. However, relative to egg weight, no measurable effect was detected due to light cycle, age or sequence length on yolk and albumen weights.

5. The paper provides new evidence suggesting that long ahemeral cycles could be used to improve egg production as well as shell thickness in flocks with modest rates of lay.     

Physical characteristics of intact and cracked eggs

1. Six egg samples, comprising equal numbers of intact and cracked eggs, were collected from three flocks of hybrid layers.

2. Cracks were classified according to type (hole, star or straight) and the weight, shape, shell colour and specific gravity of all the eggs were measured. Shell thickness and dry shell weight were also recorded for a maximum of 10 intact and 10 cracked eggs from each sample.

3. The largest proportion of cracks were holes.

4. Differences in mean egg weight and shape of intact and cracked eggs within each sample were inconsistent. Mean shell colour was darker for the intact brown eggs than for the cracked ones. For all the samples, mean egg specific gravity, shell thickness and dry shell weight were higher for the intact eggs. The difference in egg specific gravity was significant (P<0.05) for all samples.

5. Holes occurred in eggs of lower mean weight but with better quality shells than those in which star or straight cracks occurred.     

Quality characteristics of quail eggs

1. An experiment was carried out with laying Japanese quail to study the influence of age on their egg quality.

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.     

The hen's egg: Incidence and inheritance of some egg abnormalities

1. More than 9000 eggs, each laid by a known hen, were examined and malformations of six types recorded: double‐yolked, A, B, rough, shell‐less and thin‐shelled.

2. A and B malformations are those seen in, respectively, an egg that is held in the shell gland for an abnormally long period and one that reaches the shell gland while an A‐egg is still there; many of the eggs recorded as rough‐shelled were probably A‐eggs for which the corresponding B‐eggs had been lost.

3. The birds were of three strains: a medium‐body‐weight brown‐egg‐laying strain and a White Leghorn strain, both of commercial origin, and a laboratory strain of Brown Leghorns.

4. The incidences of egg malformation in the three strains were 8.3, 9.2 and 0.5%.

5. A‐, B‐ and rough‐shelled eggs constituted more than two‐thirds of all malformed eggs.

6. Evidence from two generations suggests that these malformations have a high heritability.     

Eggshell of the domestic guinea fowl

1. Physical characteristics of eggs of the domestic guinea fowl, Numida meleagris galeata, were measured and compared with those of its wild counterpart and with other birds using allometric relationships.

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 (G_H2O) remained constant.

3. Fresh egg mass (m₀), length and breadth of the egg, G_H2O and specific water vapour conductance, spG_H2O (G_H2O 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 spG_H2O was normal, the thickness of the shell being compensated for by a greater density of pores for gas exchanges.     

Whitening of brown shelled eggs: Individual variation and relationships with age,fearfulness, oviposition interval and stress

1. Fearfulness, shell colour, incidence and degree of shell whitening and the interval between ovipositions were studied in two populations of 30 brown egg laying hens with family histories of a low or a high incidence of egg shell whitening.

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.     

The relationship between hatching egg weight and subsequent performance of broiler chickens

Small eggs constitute a high proportion of the eggs laid by pullets. The literature shows that chick hatching weight is strongly correlated with egg weight, but evidence on the influence of egg weight on hatchability and subsequent performance of chicks is less certain.

The aim of this experiment was to determine the profit returned at 12 weeks by broiler chickens hatched from eggs ranging in weight from 44 g. to 58 g. at one gram intervals and to determine how competitive and separate rearing might modify the relationship.

A total of 6000 eggs were collected during 10 days from a 28‐week‐old, broiler breeding flock and graded into the above mentioned egg weight classes. From these, a total of 3480 day‐old broilers were housed. Each egg weight class was equally represented and balanced for sex.

Hatchability and fertility showed no consistent trend with egg weight for eggs above 46 g., but below the 47 g. level there was a trend of declining fertility and hatchability.

A strong positive relationship was found between the weight of the chick at 1 day of age and egg weight for both males and females with no significant difference overall in body weight between the two sexes.

Body weight to 12 weeks was found to be strongly related to egg weight, in a linear fashion, though this influence declined with age.

There was a greater influence of egg weight on body weight at all ages in the separate rearing treatment compared with competitive rearing but this was not significant after 10 weeks.

Egg weight had an important bearing on body weight and profit at 12 weeks, but no effect on food conversion or mortality.

The increased profit over food costs per 100 day‐old chicks was found to be 52.75 cents for the separately reared birds respectively for each 3 g. increase in egg weight.     

Influence of dietary magnesium content on laying performance and egg shell magnesium content in the domestic hen

1. The effects of feeding diets containing various amounts of magnesium on laying performance in the domestic hen were investigated.

2. A reduction in egg number, egg mass, egg shell thickness and egg shell magnesium content occurred in birds receiving diets containing either 207 or 132 mg Mg²⁺/kg even though the duration of egg formation was unaffected.

3. The progressive increase in magnesium content normally observed towards the outer surface of the hen's egg shell was not present in birds receiving a diet containing 207 mg Mg²⁺/kg.     

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.     

Interrelationships between shell quality and egg production and egg and shell weights in white leghorn and white rock hens

Interrelationships between shell quality, production rate, egg and shell weights in relation to seasonal changes were compared in White Leghorn (WL) and White Rock (WR) hens. An increase in the average egg weight was observed in both breeds during the hot summer months. The weight and quality of the shell decreased gradually in eggs laid by WL hens, but increased in those from WR during the summer.

Significant negative correlation coefficients were found between shell quality and egg weight in only the WL, when analysed on the basis of individual averages for the entire experimental period and on weekly averages for the breed. No significant correlation was found between shell quality and production rate in WL hens. Great variabilities were obtained between individual birds regarding the correlations between shell quality and egg weight and between shell quality and production rate, when calculated on the basis of seasonal changes in both breeds.

Multivariate analysis, in which shell quality was correlated with the other variables in all combinations possible, supplied a wider explanation than the simple correlations calculated.

The differences between the two breeds are discussed.     

Genotypic differences in speed and magnitude of response to ahemeral lighting

1. The paper compares between three genetically different lines in their egg weight and shell thickness response to a 28‐h cycle.

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.     

The effects of feeding regime and stocking rate on the performance of medium‐bodied layers in the humid tropics

1. The effects of housing laying hens 1 or 2 per cage (1 452 or 726 cm² /bird), and three feeding regimes (ad libitum, 70% ad libitum and 6 days/ week) were investigated.

2. With 2 birds/cage egg production and food utilisation were adversely affected, but there were no significant effects on egg weight, food consumption, shell thickness, body‐weight change, mortality and abdominal fat.

3. Food restriction significantly increased body‐weight loss and decreased egg production, food consumption, final body weight and abdominal fat, but had no significant effect on egg weight, shell thickness and mortality. The effect on food utilisation was inconsistent.

4. There were significant interactions between feeding regime and stocking rate for egg weight and final body weight.

5. It is suggested that in the humid tropics birds caged singly could be fed at 70% ad libitum while those caged in pairs should be fed ad libitum to avoid multiple stress.     

Egg Shell Strength

Three experiments are reported which were designed to measure the relationship that exists between the specific gravity of an egg and deformation of its shell under load and also to determine the extent to which these two egg characteristics are related to shell breakage in the field.

A very close relationship was shown to exist between egg specific gravity and egg shell deformation.

In experiments 1 and 2, measurements of specific gravity and shell deformation were performed upon samples of eggs produced by groups of birds housed in wire‐floored pens and by individual birds kept in battery cages and were found, with one exception, to be significantly related to the incidence of cracking under these field conditions. The one non‐significant correlation was that between egg shell deformation and percentage cracks among eggs from the various pens of birds. However, too much emphasis should not be placed on this latter result because the incidence of floor‐laying in the different pens was not uniform and this increased chance variation in the occurrence of cracking.

In experiment 3 specific gravities and shell deformations were determined on 3000 sound eggs before they were subjected to treatments that simulated the hazards encountered during (a) laying in battery cages, (b) transport in the conventional travelling boxes. Both measurements were found to forecast fairly accurately the probability of a particular egg becoming cracked or remaining sound during the treatments.

The results confirm that egg specific gravity, as measured by the hydrometer method, is a reliable assessment of shell strength and suggest that the measurement of shell deformation is of comparable reliability. Other factors of practical significance that would influence the choice between the two assessments are discussed.     

Performance of a deep litter system for egg production

1. Medium hybrid hens were housed from 20 to 64 weeks in a deep litter house as flocks of 300, 370 and 370 and at stocking densities of 2–4 to 10–7 birds/m² in three successive laying cycles. Sister birds were housed in cages in an adjacent building as groups of 3 and 4, at 750 or 560 cm²/bird.

2. Hen housed egg production was lower on litter (208 to 235) than in cages (230 to 253). However, the estimated 52‐week values for litter were comparable to or better than standards published by the National Farmers’ Union.

3. Ambient temperatures were well controlled in both houses, but atmospheric dust and ammonia were a problem in the litter system and ammonia was a problem in the deep pit cage house. Litter condition was good at all stocking densities.

4. There was a trend for production to increase with stocking density on litter, but to decrease in cages.

5. Most egg quality variables were similar in the two systems, although there were more dirty eggs from litter and shell thickness was slightly greater in eggs from cages.

6. Body weight increase was initially faster in birds on litter; caged hens were equally heavy by the end of lay, but a greater proportion of their body mass was lipid.

7. The severity of feather damage and loss was correlated with stocking density for hens both on litter and in cages, being worse at the higher densities. Median cage scores were greater than values from litter at low densities but less than those from high densities. Beak trimming reduced feather damage on litter but had no effect in cages.

8. Mortality was low (1 to 3%) for all flocks, except those in year 3 which had not been beak trimmed and which suffered from cannibalism both in cages and on litter.     

Comparisons of egg quality traits,egg weight loss and hatchability between striped and normal duck eggs

1. The egg quality of striped and normal duck eggs was compared to determine why striped eggs show decreased hatchability. A total of 430 eggs, obtained from a Pekin duck breeder flock aged 50–65 wks, were used in three experiments. The eggs were weighed and assigned randomly to measure egg quality traits, egg weight (EW) loss and hatchability during incubation.

2. There were no significant differences between egg types in terms of egg shape index, eggshell strength and thickness, albumen height, Haugh unit, yolk colour, weight of the eggshell with or without membranes, calcium, phosphorus, copper and manganese contents in the eggshell (with the inner and outer membranes or without the inner membrane), albumen weight, dry matter of albumen, crude protein (CP) of thick albumen and pH of the thick albumen.

3. The weight of eggshells with membranes, weight of thick albumen and CP of thin albumen in striped eggs were lower than those in normal eggs.

4. The thin albumen in striped eggs was heavier than that in normal eggs. The pH of the thin albumin in striped egg was significantly higher than that in normal eggs.

5. There were no significant differences in EW loss during incubation or duckling weight between striped and normal eggs. However, the hatchability of striped eggs was lower.

6. The lower weight of the eggshell inner membrane and thick albumen, lower CP content and higher pH in the thin albumen of striped eggs might contribute to lower hatchability.     

Egg‐shell deposition and blood plasma inorganic phosphorus concentration in individual laying hens

1. The relationship between plasma inorganic phosphorus measured at the end of the dark period and the weight of the next egg shell produced was investigated in 30 Hisex Brown hens.

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.     

Factors affecting the weight and water status of the chick at hatch

1. Variation in chick weight at the moment of escape from the shell is accounted for by the fresh weight of the egg, the weight lost from the egg during the incubation period and the weight of the shell and residues at hatch.

2. Over 97% of the variation in chick weight at hatch can be explained by two factors, fresh egg weight and weight loss during incubation. These two factors still account for a high (87%) proportion of the variation in chick weight at 21 d after setting when chicks would normally be removed from the hatcher.

3. The water content of the true chick and the residual yolk sac are both affected by water loss from the egg during incubation and account for the differences in the weight of the whole chick at hatch from eggs of the same size.

4. When the fluid reserves within the egg become exhausted in the few days before hatch, the water: dry weight ratio of the yolk rather than embryo is maintained despite variation in water losses between eggs.     

Relationships between age,shell quality and individual rate and duration of shell formation in domestic hens

1. The duration and rate of shell formation was measured individually in each of 44 hens. Comparisons were made between hens of different ages, and also between hens which laid eggs of differing shell qualities.

2. Shell formation began 9–5 to 11 h after the oviposition of the previous egg, increased linearly for 13 h and then plateaued at 1–5 h before oviposition.

3. The variation in egg shell quality observed in two experimental groups of hens was 75% attributable to differences in the rate of shell deposition and 25% attributable to difference in the duration of shell deposition.

4. The mean interval between ovipositions increased with age but neither shell weight, nor rate or duration of shell depositon were affected. The increase in egg weight with age accounted for the decrease in shell quality.

5. Intervals between ovipositions were positively correlated with the duration of shell formation, especially its latter stages.

6. Egg production was negatively correlated with the interval between ovipositions but not with the duration or rate of shell deposition. There was a negative correlation between duration and rate of shell deposition, except in the case of the hens producing eggs of poor shell quality.     

Effect of strain and age on the relationship of oviposition time to shell strength

1. The relationships between oviposition time and specific gravity, shell thickeness, deformation and breaking strength of eggs from six commercial layer strains were examined after 6 and 12 months of production.

2. Shell strength, assessed by any of the methods, was relatively low in eggs collected at 10.00 h and was generally successively greater in those collected at 12.00, 14.00 or 16.00 h. Over the same period egg weight decreased.

3. These time‐related changes in shell strength were similar for the two production ages despite the difference in shell quality due to age.

4. No consistent significant differences were observed between strains in time of oviposition.     

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).