Different characteristics in chick embryos of two broiler lines differing in susceptibility to ascites

1. The relationship between the length of incubation, hatching, hypoxic condition, thyroid hormones and the occurrence of ascites were studied in embryos of 2 broiler lines differing in susceptibility to the ascites syndrome.

2. Both the time of external pipping (ep) and hatching of embryos from the ascites‐resistant (AR) broiler line was earlier compared to the ascites‐sensitive line (AS). The interval between internal pipping (ip) and ep was the same between the lines, but the interval between ep and hatching was shorter in the resistant line.

3. The T₃ and T₄ concentrations in plasma of the AS line were lower compared to the AR line.

4. Analyses of partial pressures of oxygen (pO₂) and carbon dioxide (pCO2) in the air cell of the egg revealed that at day 18 the AS embryos had lower pO₂ and higher pCO₂ concentrations compared to the AR embryos.

5. The delay in hatching of the AS embryos might induce a more pronounced and/or extended hypoxic environment, thereby creating an environment that evokes ascites.     

The hatching sequence of Ostrich (Struthio camelus) embryos with notes on development as observed by candling

1. The hatching sequence of the ostrich (Struthio camelus) was determined by observing embryos during candling, those in the process of hatching and in dead‐in‐shell eggs.

2. Candling showed that there was a progressive increase in dark shadowing within the egg but fine details were not easily seen. Nevertheless candling is considered to be an important method of assessing development of ostrich eggs during incubation.

3. The ostrich embryo adopts a hatching position and follows a hatching sequence different from that of the fowl. During internal pipping, the air space is pulled towards the beak in the former but the beak moves to the air space in the latter. The right foot has an important role in breaking the shell during hatching.

4. The hatching process is considered to reflect an adaptation to the egg having a hard, brittle shell.

5. Malpositions in the ostrich may have been misinterpreted in the past because of the unusual hatching position. The commonest malposition described here was head‐in‐the‐small‐end.     

Storage of hatching eggs: The effect on total incubation period

1. A time‐lapse photographic technique has been developed which enables routine recording of the hatching times of up to 192 chicken embryos.

2. Storage of eggs for 14 d caused a delay of 134 h in the mean total incubation period.

3. Female embryos hatched about 3 h earlier than males in the non‐stored eggs but there was no difference between the sexes in eggs stored for 14 d.

4. Rate of weight loss during incubation was similar in both non‐stored and stored eggs: there was no relationship between weight loss at 19 d incubation and total incubation period.

5. Hatchability of fertile eggs was 19.5% lower in eggs stored for 14 d and proportionately more embryos died between 4 d and 18 d incubation than in the non‐stored eggs.     

Traits influencing the hatching performance of Japanese quail eggs

1. Japanese quail eggs from moderately heavier sires showed superior fertility; while fertile eggs from moderately heavier dams hatched slightly better than the eggs from lighter dams.

2. Higher rates of fertility and hatchability of Japanese quail eggs were observed from parents of 10 to 19 weeks of age, with peak fertility and hatchability at 14 and 12 weeks of age, respectively.

3. Sex ratios of 1:2 to 1:5 gave comparable fertility and hatchability results.

4. The hatching performance of quail eggs from cage and deep litter reared breeders was comparable.

5. Fertility and hatchability were directly proportional to the egg weight.

6. Quail egg shell colour, tints and blotches were found to influence hatching performance.

7. Storing quail eggs at 16 ± 2°C and 75 ± 5% relative humidity for more than 4 d reduced hatchability.

8. Hatchability of eggs stored at room temperature was improved if they were sealed in polyethylene bags.

9. Provision of light during the first 14 d of incubation resulted in a photo‐acceleration of about 3.2 h.     

Performance of lines selected for fast‐and slow‐hatching times and crosses among them 1

1. Males of a control line and two lines selected for fast‐ and slow‐hatching were mated to females of the same three pure lines and three crosses between them. Hatchability, egg weight and hatching time were measured.

2. No significant differences were found between genetic groups in hatchability.

3. Groups containing the fast‐hatching line genotypes were significantly smaller in egg weight than those not containing this line.

4. Significant differences in hatching time existed between male lines and between female lines within pure and cross‐line parent types while no differences were observed between the female parent types and no interactions of male by female lines occurred.

5. It was concluded that inbreeding in the pure lines (10%) did not affect any of the variables measured.

6. The results on hatching time support the conclusion that little genetic variance other than additive variance is involved for this trait.     

Explanted embryo culture: In vitro and in ovo techniques for domestic fowl

1. Embryos of the domestic fowl (72 h old) have been explanted into shell‐less cultures or ‘surrogate’ eggshells, in order to investigate the possibility of rearing these embryos to hatching.

2. Rocking embryo cultures during the first half of incubation enhanced embryo growth.

3. Embryos explanted into ‘surrogate’ eggshells of either other individuals or other species have been successfully ‘hatched’.

4. A normal chorioallantois is formed in these surrogate eggshells. This enables a functional albumen sac to form and eggshell resorption to be achieved.

5. Embryos grown in ‘surrogate’ eggshells are slightly smaller than controls but otherwise normal.

6. The technique provides opportunities for genetic engineering experiments.     

Effects of ethylnitrosourea on the hatchability and survival of chicks

1. Two experiments were carried out to study the effects of the mutagen ethylnitrosourea (ENU) at concentrations of 1.4 to 3 500 μg in 0.3 ml of saline (experiment 1) and 585 to 1 170 μg in 0.1 ml of saline (experiment 2) on hatching eggs of two breeds of fowls. Hatchability (experiment 1) and survival up to 7 d of age without food (experiment 2) were assessed. In experiment 1 the hens were fed on different diets prior to providing the hatching eggs.

2. The mutagen showed a non‐linear effect upon the hatchability, higher doses being less effective than small doses.

3. In the majority of cases, female embryos were more sensitive to the effect of ENU then male.

4. The mortality after hatching was also affected by ENU; the chicks from treated eggs surviving without food better than controls.     

In ovo oral vaccination with cmpylobacter jejuni establishes early development of intestinal immunity in chickens

1. Chick embryos were orally immunised at day 16 of incubation by injection of heat‐killed Campylobacter jejuni organisms into the amniotic fluid. The response to vaccination was observed at 5 d after hatching or, in some birds which received a postnatal oral booster vaccination, at 7 d after hatching, and the response was observed at 14 d of age.

2. The titres of antibody in serum, bile and intestinal scrapings, the distribution of immunoglobulin‐containing cells in the spleen, duodenum and ileum and the expression on peripheral blood leukocytes (PBL) of the T cell surface markers CD3, CD4 and CD8 were determined.

3. Whereas low titres of anti‐flagellin antibody were detected in serum, bile and intestinal scrapings of unimmunised birds, high titres were observed in immunised birds.

4. An increase in antibody of all isotypes was detectable in serum but the elevation in IgA antibody in intestinal scrapings and bile was particularly striking. This response was reflected in a dramatic increase in immunoglobulin‐containing cells, detected by fluorescent histology, particularly diose associated with IgA and IgM isotypes in the spleen and intestine of immunised birds.

5. Secondary oral boosting after hatching resulted in a depression in serum anti‐flagellin antibody in immunised birds compared to pre‐boosting titres (although still significandy higher than in non‐immunised controls) but an increase in IgA antibody in intestinal scrapings and bile. The number of immunoglobulin‐containing cells was also increased after boosting.

6. Neither immunisation regimen caused a significant change in the numbers of circulating CD3, CD4 or CD8 T cells.

7. These results indicate that in ovo oral immunisation with C. jejuni antigens stimulates the precocious development of immunity in chicks.     

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.     

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.     

Manipulations of germ‐cell populations in the gonad of the fowl

1. Embryos of the domestic fowl have been partially sterilised by injecting the drug busulphan into 24‐h incubated eggs.

2. Some of these embryos were injected with primordial germ cells (PGCs) after 55 h of incubation to attempt to repopulate the gonads.

3. Primordial germ cells transfected with a defective retrovirus containing the reporter gene lac Z were shown to settle in these sterilised gonads.

4. Quantitative histology of 6‐d embryos showed that busulphan produced 75% sterilisation but that PGCs could repopulate these gonads.

5. The technique of producing such germ line chimaeras is of value in studying cell kinetics, gonad differentiation and the production of transgenics.     

The effects of restricted feeding on adrenal cortical activity in the immature domestic fowl

1. The effect of reducing food intake to 75% of the ad libitum intake was determined from hatching to 8 weeks in young Light Sussex chickens.

2. Restricted birds were lighter throughout the experiment.

3. Relative adrenal weight tended to be greater in restricted birds but the difference decreased with time.

4. There was no depletion of adrenal cholesterol: from week 5 there was a significantly greater amount in the adrenals of restricted birds.

5. After 1 week of restriction plasma corticosterone concentration was 73% greater than in controls. It decreased progressively, falling within the normal range at 5 weeks.

6. Restricted birds were hypoglycaemic from weeks 2 to 7 and hyper‐lipacidaemic throughout. A negative correlation between plasma glucose and free fatty acids was found.     

The effect of dietary bacitracin on the incidence of streptococcus faecalis subspecies liquefaciens and related streptococci in the intestines of young chicks

1. A study has been made of changes occurring in the numbers and types of faecal streptococci in the intestines of chicks from hatching to 23 d of age, when fed on a diet containing 50 mg bacitracin/kg.

2. It was found that Streptococcus faecalis sub‐species liquefaciens predominated in chicks prior to feeding and in control birds the organism remained as a significant part of the flora throughout the experiment.

3. Strep. faecalis s.s. liquefaciens was not found after the first week in birds given dietary bacitracin.

4. Although outnumbered initially in the caeca by Strep, faecalis s.s. liquefaciens, other streptococci were present at 10⁶ to 10⁷/g contents from 14 d onwards in both control and bacitracin‐treated birds; these included Strep. faecium biotypes and two other unidentified but related groups.

5. Tests made in vitro showed that Strep. faecalis s.s. liquefaciens was more sensitive to bacitracin than Strep. faecium.

6. The possible effects of Strep. faecalis s.s. liquefaciens on the developing bird are discussed.     

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.     

Composition and amino acid content of carcass,skin and feathers of the growing gosling

1. Growth rate, food intake and utilisation were determined for goslings (Anser cireneus) from hatching to 7 weeks of age.

2. The relative weight of the carcass (body without feathers, skin or intestinal content) decreased from 0.83 of total body weight at hatching to 0.73 at 7 weeks. The skin relative weight increased from 0.12 at hatching to 0.17 at 2 weeks of age and subsequently remained constant. The weight of feathers increased from 0.034 of body weight at hatching to 0.08 at 7 weeks.

3. The fat of the carcass and skin increased during the 7‐week experimental period. The skin retained about half of the total body fat.

4. While amino acid compositions of feathers and skin proteins were quite similar to data reported for other birds, carcass proteins were lower in methionine and lysine.     

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.     

Fumigation of poultry food with methyl bromide: Effects on egg flavour,number and weight

1. Rhode Island Red females were fed, from hatching, on diets which had been fumigated with methyl bromide at the concentration recommended for the elimination of salmonellae or at 1 1/2 times this value.

2. Body weight, egg weight or egg number were not significantly affected by treatments, but sexual maturity may have been slightly delayed.

3. There was some evidence of an adverse effect on egg flavour, particularly by the trained sensory panel.

4. Principles of experimental design for this type of experiment are discussed.     

The method of chicken whole embryo culture using the eggshell windowing,surrogate eggshell and ex ovo culture system

1. The unique accessibility of the avian embryo have made them an ideal model for the study of development and genome editing. Chicken whole embryo culture has provided important insights into toxicity tests, gene manipulation, clarifying gene functions, cell transplantation and cell tracking.

2. A simple technique for chicken manipulation is eggshell windowing, without or with seal, the latter having demonstrated some improvement in hatching rates.

3. Likewise, a surrogate eggshell system provides an accessible model for manipulation during chicken and quail development, with a higher hatchability compared to the simple windowing method.

4. The development of the chicken ex ovo culture systems in a synthetic environment as an efficient technique for imaging and microsurgery applications has enabled the study of important events of live chicken embryos at a specific time point.

5. This short review illustrates recent applications of well-designed whole embryo culture systems as a robust model for research into numerous biological mechanism, drug discovery, gene manipulating and production of functional proteins.     

Development of the small intestine in heavy and light strain chicks before and after hatching

1. Intestinal development was examined in Arbor Acres and Lohmann chicks from one week before hatching until one week after. Changes in morphology and concentrations of DNA, RNA and protein in the duodenal tissue were determined.

2. Villus height and perimeter increased 9 to 11 fold from day 14 of incubation until 7 d after hatching. Arbor Acres chicks had values which were consistently higher than Lohmann chicks.

3. DNA concentration of duodenal tissue increased with age in parallel to the increase in the number of enterocytes per villus. In the pre‐hatch period tissue activity as indicated by RNA/DNA, and ribosomal capacity as shown by the RNA/protein ratios, were high for both strains; values for Arbor Acres embryos and chicks were greater than for Lohmann.

4. DNA concentrations, RNA/DNA, RNA/protein and protein/DNA ratios correlate with morphological measurements and can be used as additional criteria for evaluating development in chick intestine.

5. In the last week of incubation and immediately after hatching, intestinal growth appears to arise mainly from cellular hyperplasia and not from cellular hypertrophy. Intestinal development patterns were similar for both strains but growth was more rapid in Arbor Acres chicks.     

Inheritance of body weight and rate of gain in Japanese quail

1. The effects of hatch date, location and sex on the body weight and rate of gain in Coturnix coturnix japonica were examined.

2. The data conformed to a mixed model and adjustments were made for the fixed effects sex, hatch date and location. Adjustment improved the precision of the estimates by reducing the error variances significantly.

3. Rearing equal numbers of birds from each family at different locations made the interactions negligible.

4. Weight gain was greater if illumination intensity up to 35 d was less.

5. Females were not heavier on the 1st day but were heavier on the 14th and 35th days than males.

6. Variance components and genetic parameters were estimated.