The influence of sample size on the choice of method and interpretation of incubation experiments

1. An equation relating batch size to between‐treatment differences has been adapted for hatchability studies and its implications for research considered.

2. Very large egg batches are required to detect small improvements in the hatchability of good hatching strains.

3. Small‐scale laboratory studies on hatchability are best confined to strains and species of low hatchability in which larger between‐treatment differences may be expected.

4. The results of hatchability studies should always be subjected to tests of statistical significance.

5. There is a strong case for studying continuous variates in the laboratory before proceeding to large‐scale hatchability studies.     

Genetic inferences from inter‐strain crossing for hatchability and fertility in white leghorns

1. Heritability estimates for hatchability of fertilised eggs were obtained from four White Leghorn strains and their crosses.

2. Based on the variance of the full‐sib family means, the heritability estimates for pure‐bred, cross‐bred and for the combined data were 0.lb186 ± 0.lb105, 0.lb065 + 0.lb021 and 0.lb088 + 0.lb005, respectively: the results showed absence of non‐additive genetic variance for hatchability.

3. Fertility was influenced more by sire strain than by the dam while hatchability was primarily influenced by the dam strain.

4. The sire x dam interaction effect was significant for fertility but not for hatchability.

5. Fertility was influenced by crossing two divergent strains.     

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 pre‐incubation treatment on hatching results of broiler breeder eggs produced at 37 and 59 weeks of age

1. The influence of temperature in the nest box, temperature during storage, storage time and pre‐setting temperature on the hatchability of broiler breeder eggs produced by birds of 37 and 59 weeks of age was examined.

2. All treatments that can be characterised as being less optimal for embryo survival than the control treatment affected the hatchability of fertile eggs more in the case of eggs produced by older birds.

3. A higher temperature in the nest box, longer storage periods, higher storage temperature, especially at longer storage periods, and higher pre‐setting temperature significantly reduced the hatchability of fertile eggs from the older birds.

4. For the younger birds, a significant reduction of hatchability was found only for the longest storage period.     

Increasing hatchability of turkey eggs by injecting eggs with pyridoxine

1. In field trials, eggs from two flocks of Large White turkey hens were injected with about 0.2 ml saline solution containing 600 μg of pyridoxine hydrochloride in order to examine its effect on hatchability.

2. Also, in an aseptic laboratory trial, eggs from Large White turkey hens were injected with 0.2 ml of saline solution and 0.2 ml of saline solution containing 600 μg of pyridoxine hydrocholoride.

3. In field trials, hatchability of pyridoxine‐injected eggs was 4.6% higher (P<0.05) than the control (non‐injected) eggs.

4. In the aseptic laboratory trial, hatchability of pyridoxine‐injected eggs was 4.2% higher (P<0.05) than saline‐injected and control (non‐injected) eggs.     

The bacterial flora of unhatched eggs

1. The methods of bacteriological examination of hatchery waste eggs were compared.

2. Using one of these methods a survey was conducted on eggs which had failed to hatch from commercial hatcheries.

3. An assessment of the level of contamination in the eggs examined indicated an average level of contamination of 12.7%.

4. The contaminating flora was composed mainly of Micrococcus sp. and Enterobacteriaceae, with Streptococcus sp., Staphylococcus sp., Bacillus sp. and Pseudomonas sp. present at lower levels.

5. Various interrelationships between contamination and hatchability are discussed.     

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.     

Microbial spoilage of ostrich (struthio catnelus) eggs

1. The incidence of microbial spoilage was investigated in three batches of ostrich eggs, one from Africa and two from Europe.

2. 18% to 21% of eggs in each batch were contaminated with bacteria and fungi, with the latter being found more often in eggs which contained more advanced embryos.

3. Although infertility and prolonged storage reduced hatchability, the high inci dence of microbial contamination in ostrich eggs is deemed to be a significant problem.

4. Improving nest hygiene is considered to be the simplest way to reduce microbial spoilage.     

Rate of decline in hatchability with preincubation storage of chicken eggs depends on genetic strain

1. The effect of preincubation storage of chicken eggs on hatchability was studied in an Australorp subline (ASS) that had shown a steady decrease of hatchability compared with the original selection line (AS) since its derivation 10 generations ago. The AS line was also included in the study.

2. Eggs were collected over 21 d and the collected eggs were stored at 10° to 12°C and relative humidity of 70 to 80% until they were set together on d 21. Fertility and hatchability of fertile eggs were calculated for each d of collection to study their relationships with age of eggs (length of storage).

3. The hatchability of fertile eggs was considerably different between the two lines in the average over 21 d and, more importantly, in the pattern of decline with length of storage.

4. In the first 3 to 4 d of storage, hatchability was very similar between the lines. However, it decreased linearly at a rate of 1.9% per day of storage over the 21‐d period in the ASS line (average 65.9%), whereas in the AS line (average 78.6%), it stayed at around 84% up to 12 d of storage, when it started to decline at a similar rate as in the ASS line.

5. Fertility was 2.6% higher in the AS line than in the ASS line, but in each line showed no significant trend with age of eggs.     

Effect of egg composition on hatchability and on growth and slaughter characteristics of meat-type chicks

1.?Using the so-called TOBEC (Total Body Electrical Conductivity) method, which allows the determination of egg composition in vivo, correlations between egg composition, hatchability and hatched chicks’ development were studied.

2.?A total of 1500 hen eggs (Ross-308) were measured by TOBEC, and eggs with extremely high (10%, n = 150), extremely low (10%, n = 150) and average (10%, n = 150) electrical conductivity values were chosen for further investigation.

3.?During the incubation period, it was observed that eggs with high electrical conductivity had a significantly higher mortality than eggs with low electrical conductivity.

4.?It was observed that both the increase in electrical conductivity at the same egg weight, and the increase in egg weight at the same electrical conductivity resulted in an increase in the hatching weight.

5.?It was found that the dry matter, protein and fat content of the chicks hatched from eggs with low electrical conductivity was higher at hatching than that of the chicks hatched from eggs with high electrical conductivity.

6.?At 42 d of age the liveweight of cocks and pullets hatched from eggs with low electrical conductivity was 3·2 and 8·2% higher than the liveweight of cocks and pullets hatched from eggs with high electrical conductivity.

7.?Because of the higher liveweight at slaughter, there was a significant superiority of the chicks hatched from eggs with low electrical conductivity in the case of the examined carcase traits at slaughter.

8.?Similar tendencies were found also in the ratios of carcase variables to liveweight, but the between group differences were not statistically significant in this case.

9.?Based on the results it was concluded that TOBEC seems to be a useful method for separating eggs with different composition.

10.?This could be a good starting point for further in vivo investigations in order to clarify the effect of egg composition on hatchability and further development.     

Effect of oiling on internal quality of eggs stored at 28 and 12°G

1. The effects of spraying linseed oil on naturally clean eggs, subsequently stored for 24 d at 28 °C were studied.

2. Oiling slowed the decline in albumen height (Haugh units) to that which occurred in unoiled eggs stored at 12 °C.

3. Oiling slowed the increase in albumen pH equally at 28 and 12 °C.

4. Oiling markedly decreased the weight loss of eggs stored at either temperature.

5. Oiling and temperature of storage were without effect on the whipping volumes of either albumen or unseparated albumen and yolk.     

Cooling of broiler hatching eggs during incubation

1. Broiler hatching eggs were cooled to 22°C for periods of 8 or 24 h on day 16 of incubation. Cooling had no significant effects on hatchability or chick quality compared with controls.

2. Cooling to 22°C for 24 h on days 14, 15, 16, 17 or 18 yielded similar results but cooling on day 13 increased late embryonic mortality.

3. When eggs were cooled to 22°C on day 16 of incubation there were no major differences in hatchability up to 48 h of cooling but chick quality deteriorated rapidly after 30 h and the limit for embryonic survival at this temperature was about 72 h.

4. There were no significant differences when eggs were cooled on day 16 and held for 24 h at 21.1, 23.9 or 26.7°C but hatchability and late deaths were significantly affected by cooling to 18.3°C.     

Battery cage shape: Its effect on diurnal feeding pattern,egg shell cracking and feather pecking

1. Battery cages 460 mm in depth (deep) were compared with 305 mm cages (shallow); the two shapes provided equal areas per bird.

2. More eggs were produced per hen housed from 30 to 70 weeks in the shallow cages; the difference approached significance.

3. The pattern of feeding activity over the day was significantly more U‐shaped in the shallow cages; this pattern accords more closely with physiological requirements.

4. Feather damage caused by pecking was slightly but significantly more severe in the deep cages at 70 weeks.

5. The proportion of cracked eggs (collected from 60 to 70 weeks) was significantly lower in the shallow cages.

6. The arrangement of the hens was such that within the shallow cages a higher proportion of birds was present in the front half.

7. It is suggested that some of the advantages conferred by the shallow cage may be related to the greater accessibility of the food trough.     

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.     

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.     

Ostrich (Struthio camelus) embryonic development from 7 to 42 days of incubation

1. Hatching success of ostrich eggs is poor (50–60% of fertile eggs). The current study was designed to identify the timing of key stages in the development of the ostrich embryo.

2. Growth of both embryo and wing length during 42 d of incubation was comparable and approximately linear, with a more or less weekly doubling in size up to 35 d of incubation.

3. The embryo eye size increased more rapidly than beak length and reached a maximum of ~16.2 mm by 28 d of incubation, whereas beak length increased continuously until hatching at 42 d.

4. Linear regression equations were derived from morphometric measurements of embryos between 7 and 42 d.

5. Information stemming from these results can be used to estimate the age of dead-in-shell embryos in an attempt to identify timing of incubation problems that potentially result in low hatchability of fertile eggs.     

Artificial insemination of Bobwhite quail

The purpose of this study was to determine whether fertilisation of Bobwhite quail could be secured by artificial insemination. After this proved to be feasible, the period between insemination and the onset of laying fertile eggs, the time during which fertile eggs were laid and levels of fertility and hatchability of eggs obtained from hens inseminated at weekly intervals over an extended period of time were determined.

Semen was collected from Bobwhite quail males by simultaneously applying pressure to both the left and right sides of the vent without prior stimulation. Upon collection, the semen was diluted with 0.9 per cent saline solution to prevent dehydration. Semen volume measurements were made with a tuberculin syringe to which was attached a piece of graduated, fine‐bore plastic tubing. Females were artificially inseminated by placing the diluted semen in the posterior opening of the everted oviduct.

Mean duration of fertility of the eggs from six trials, two of which utilised only a single insemination, one of which was the final insemination of a series of weekly inseminations and three of which utilised two inseminations within a period of 24 hr, was 9.3 days. Percentage fertility of eggs improved considerably after the first trial probably due to improvement of technique and gain in experience. Average fertility of eggs for the six trials was 64–9 per cent.

The average time interval between insemination and the appearance of the first fertile egg was 3.4 days. Peak fertility was reached by the fourth day following insemination.

Fertility of eggs averaged 62.2 ±3.5 per cent and their hatchability averaged 77.2 ±1.4 per cent over a period of 31 weekly inseminations. These values were comparable to 60.2 per cent fertility and 78.9 per cent hatchability which were obtained from natural matings.     

Factors affecting hatchability during commercial incubation of Ostrich (Struthio camelus) eggs

1. A batch of 320 ostrich eggs from 9 different farms in Zimbabwe were incubated in a single stage operation and the fate of each was recorded.

2. Hatchability was only 37.2% and the result of high rates of infertility and contamination (22.2% and 22.8% respectively); it varied between eggs from different farms.

3. Embryonic mortality was high at the start and end of incubation, a pattern similar to that of other domestic birds.

4. Mortality of late stage embryos was related to percentage water loss and mass specific water vapour conductance of the shell, with extremes of the ranges causing the highest mortality.

5. Microbial contamination of the eggs was a significant problem and varied in eggs from different farms indicating that more attention is needed in both breeder bird and nest management.     

Effects of storage conditions on hatchability of chicken eggs in a warm climate

1. A total of 3792 eggs from AF Bosbek layer parents were used to determine the effect of storage time on the hatchability of eggs kept either small end up (SEU) or small end down (SED).

2. These eggs were stored at room temperature (27°C‐31°C) or in an air‐conditioned room (20°C‐23°C), for two, three, six or seven days and incubated in four replicate hatches.

3. Eggs kept SEU improved hatchability even for short‐term storage when temperatures were high.

4. Simple air‐conditioning can reduce the temperature sufficiently for the viability of the embryo to be preserved for up to a week.