Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
Volume 8
Issue 4
Available Online: http://www.ejpau.media.pl/volume8/issue4/art-41.html


Monika Wiercińska, Danuta Szczerbińska
Department of Poultry and Ornamental Brids Breeding, West Pomeranian University of Technology in Szczecin, Poland



The factors limiting the development of ostrich and emu farming include their relatively low hatchability but neither the stages of emu and ostrich embryogenesis nor developmental abnormalities that occur during the incubation have been adequately studied. We carried out a hatchability analysis 5 times between February and April in the emu (n=50) and between May and July in the ostrich (n=69) on two farms in Poland in 2004. The eggs were collected for 14 days, stored at 16°C and 70% relative humidity and then incubated at 36.4°C and 25% relative humidity. The dead embryos were examined and measured for basic dimensions of the body and organs, the state of embryonic membranes, malpositioning, morphological malformations, downiness, degree of yolk sack absorption as well as the appearance of the skin and internal organs. Lower hatchability from both set (49.3%±27.7) and fertilised (77.3%±27.7) eggs was found in the emu. In the ostrich, the indices were, respectively, 68.0%±23.3 and 82.9±11.3. During the incubation, 7 ostrich and 9 emu embryos died, which represented 17.1% and 20.4% fertilised eggs, respectively. Two malformed ostrich and two emu embryos have been described. The ostriches exhibited anophthalmia, cyclopia, and beak malformations, while a pair of twins shared one yolk sack. The emus suffered encephalocele, torticollis, and beak malformations, as well as conjoined twins were found. Other dead embryos had normal morphological structure, however, presented other conditions such as oedema of head and legs, unabsorbed yolk sacks and malpositioning. The study described in this paper showed that mortality of embryos and anomalies applied only to beak malformations occurring during their development were similar in both bird species.

Key words: embryo mortality, developmental malformations, avian twins, conjoined twins.


Avian embryonic mortality has long been a subject of biological interest. It is also a problem of obvious economic importance. Unfortunately, very little is known about patterns of embryonic mortality in the emu and ostrich. Problems of egg quality, hatching technology and embryonic development of the economically most important domestic birds are relatively well understood and described. On the other hand, there is no information on embryogenesis and related problems in the emu and ostrich, the species which although more and more commonly farm-bred in numerous countries are still considered exotic. The factors limiting the development of ostrich and especially emu farming include their relatively low hatchability. The knowledge on their reproduction and the grounds of pathologies occurring in the breeding of the ratites are the key factors that underlie the future of their farming.

Developmental abnormalities can result from random accidents of ontogeny, single mutations, inbreeding nutrional constraints, climatic factors or the action of compounds with teratogenic effects. The magnitude of the effects of deviations from recommended incubation conditions: temperature, humidity, turning frequency, ventilation and egg orientation contribute also to the effects manifested in embryonic abnormalities.

Neither the stages of emu and ostrich embryogenesis nor developmental abnormalities that happen during the incubation have been fully studied and described. Thus, it seems reasonable to carry out an analysis of egg hatchability in these species with particular insight into the deaths and developmental abnormalities of the embryos.


The study included eggs obtained from 6 years-old ostriches and emus bred on two private farms situated in Western Pomerania, Poland. Hatchability analysis of 50 ostrich eggs and 69 emu eggs was carried out in the middle of the 2004 breeding season. The eggs were collected between May and July in the ostrich and February and April in the emu. In each of egg sets (5 for each species), eggs of both species collected during a 14-day period were marked with sequential numbers and stored at 16°C and approx. 70% relative humidity. Before the setting, the eggs were disinfected using formalin vapours for 30 minutes. Using the results of our previous studies, the eggs of both species were incubated electronically in controlled cabinet incubators, in which the following incubation parameters were applied: 36.4°C and 25% relative humidity. After moving the ostrich eggs on incubation day 39 and the emu eggs on incubation day 49 into the hatching apparatus, the temperature was kept at the same level, relative humidity inside the chamber was raised initially by 10%, and then by further 20% on the moment when first chicks broke through the shell. The ostrich eggs were incubated vertically with the air chamber positioned upwards and turned automatically 90° every hour, whilst the emu eggs were incubated in horizontal position being turned automatically 90° every hour. During every week of incubation, the eggs were weighed in order to keep track of their weight loss, and were candled in case of the emu eggs using a noctovision camera. The time of hatching was recorded (a time-span from the chick breaking the shell until leaving it). The cases were also recorded when chicks needed help to leave the shell.

During the hatching, the emu chicks were given assistance in 2 case [9]:

Assistance to the emu chicks, basing on observations of Szczerbińska [25], was undertaken in two events only:

As soon as a chick had hatched, the chick and the remains of foetal membranes, and the metabolite litter were weighed in order to calculate their proportions in the total egg weight.

The dead embryos were examined and measured for basic dimensions of the body and organs, the state of embryonic membranes, malpositioning, morphological malformations, downiness, degree of yolk sack absorption as well as the appearance of the skin and internal organs, mainly heart, liver, lungs and kidneys. Descriptions, including a general quantification of the extent of the defect, were recorded for each abnormal specimen. All abnormal specimens were photographed as a part establishing permanent record. The tables include selected body measurements of embryos as well as weights of particular organs.

The day of death of the emu embryos was determined basing on the study by Horbańczuk [9], who has adopted that incubation time of ostrich eggs is 42 days, which corresponds to doubled incubation time of hen’s eggs. Similar method of determining the age of dead ostrich embryos, after introducing certain modifications, has been given earlier by Ar and Gefen [1]. When determining the age of emu embryos, the information contained in works of Kinder and Anthony [14] and Minnaar [16] who described selected embryogenesis stages of these birds, was used.

The indices of hatchability from set and fertile eggs were calculated as well as the rate of dead, crippled, and weak chicks. The collected data were analysed statistically using one-way ANOVA.


The daily loss of egg weight in the ostrich amounted to, the weekly one to 26.11±4.5, whereas the total loss in egg weight during the incubation was 145.5g±24.9 on the average. In the emu the egg weight losses were significantly lower. Their daily loss amounted to 1.58g±0.3, the weekly one to 11.1g±1.9, whereas the total one for about 7 weeks of incubation to 76.0g±13.1. Significant differences were found in relative egg weight loss in both species on the day when eggs were moved to hatching apparatus (Table 1). Larger losses in egg weight, by approx. 3.5%, were found in the emu.

Table 1. Weight losses in ostrich and emu eggs during incubation (±SD)


Bird species



Initial egg weight



Weight losses in incubated eggs (g)

On 7 day






On 14 day






On 21 day






On 28 day






On 35 day






On day 39 *




9.81 ±1.5


On 42 day






On day 49 *






* Loss on the day when eggs were moved to hatching apparatus
1 Mean values differ significantly (p<0.05)

Lower hatchability from both set (49.3%±27.7) and fertilised (77.3%±27.7) eggs was found in the emu. In the ostrich, the indices were, respectively, 68.0%±23.3 and 82.9±11.3 (Table 2). In total, the hatching losses (including non-fertilised eggs) in the emu constituted 50.7% of set eggs, while 32.0% in the ostrich, and were considerably higher than in other poultry species.

Table 2. Hatching results (±SD)


Bird species




set [n]

fertilised [n]










Duration of incubation time









Time of hatching [h]



Number of chicks

hatched unaided

hatched with the assistance







Chick weight

absolute [g]

relative [%]







Weight of post-hatching remnants

absolute [g]

relative [%]







Crippled and weak chicks [%]



Dead embryos [n]



Dead embryos [%]



Hatchability [%]

from set eggs

from fertilised eggs







* Means in rows values differ significantly (p<0.05)

The time of hatching in the emu chicks was shorter then in the ostrich ones by about 6 hours. The help at hatching was given to 5 emu chicks and to twice as large number of ostrich chicks. The weight of chicks was similar, being 67.6% and 68.4% of hatching egg weight in the emu and the ostrich, respectively. The analysis of post-hatching refuse showed that the remnants of foetal membranes and the metabolite litter, defined as post-hatching remnants, was twice as much in the emu than in the ostrich. The embryo deaths in the ostrich and the emu were similar, amounting to 17.1% and 20.4% of fertilized eggs, respectively.

The pathomorphological analysis of embryos showed developmental abnormalities in two emu embryos and two ostrich ones during the whole hatching period. In case of the latter, it was found that embryos were dying mostly in last days of the hatching (n=5, 71.4%). Their age was determined at about 40th-42nd day of incubation. Merely one ostrich embryo (14.3%) died in the initial stage of embryogenesis (Table 3, 21S) and one (14.3%) about 35th day of incubation (Table 3, 50S).

Table 3. Analysis of dead ostrich embryos

The time of dying in the emu embryos was more differentiated than in the ostrich (Table 4). The embryos which died in two first weeks of incubation constituted 33.3% of their overall number. Their body weight, due to different times of dying, ranged 0.17 to 3.25 g. Among 5 embryos which died after 21st day of incubation, four (44.4%) died in the last several days of hatching. Three of them did not break through into the air chamber, whereas the one – after breaking the inner shell membrane (peri-albumen membrane) – breathed with its lungs and its yolk sack was fully absorbed (Table 3, 87d).

From among the embryos that died in the late stage of embryogenesis, i.e. such ones which should have already assumed terminal position for hatching, two were malpositioned in the egg (Figure 1 and 2). The head of the emu embryo was in the sharp end of the egg (Table 4, 28b), whereas the ostrich embryo stayed admittedly lengthways the egg but its beak had been directed towards the left leg (Table 3, 23S). Both embryos proved to be fully developed, with complete plumage, and the time of their dying was determined at day 50 in the emu and day 42 in the ostrich.

Figure 1. Malpositioning of emu embryo with the yolk sack

Figure 2. Malpositioning of ostrich embryo in egg

From among the embryos with unabsorbed yolk sacks (Figure 1 and 3), the contents of one yolk sack was of greenish colour (Table 3, 23d). This embryo died at about 50th day of incubation; apart from torticollis (Figure 4), it was large with complete downiness and positioned correctly. Moreover, there was much not used jelly-like matter in the egg, while the embryo’s organs showed haemorrhages (Table 4, 23d). In the one of ostrich embryos (Table 3, 23S), which died in the final stage of incubation despite its normal morphological structure, dilatation of intestines was observed as well as many uric deposits in the peri-cloaca region and large amount of white-green faeces in the cloaca.

Figure 3. Ostrich embryo with the yolk sack unabsorbed

Figure 4. Emu embryo with torticollis

Table 4. Analysis of dead emu embryos

Most of the ostrich embryos (n=6, 85.7%) that died in the late stage of embryogenesis showed jelly-like swellings (oedemas) of the head and limbs (Figure 5), which would point at disturbances in water evaporation process from the egg. In the presented material there is a case of ostrich that died closely before the hatching (Table 3, 12S), in which developmental malformations were found within its head: deformed cranium with cerebral hernia (exencephaly), lack of eyes (anophthalmia), and abnormally developed beak (beak malformations), with the upper sheath clearly shorter than the lower (Figure 6).

Figure 5. Jelly-like swellings (oedemas) in the neck and lim

Figure 6. Exencephaly, anophthalmia and beak malformations

While analysing dead embryos, two cases of twin embryos were found in the emu and the ostrich. The occurrence of bird twins is not included among anomalies; however in both cases the embryos were deformed. The conjoined twins of emu (Figure 7) died at about 32 days of incubation and had joined thoraxes with shared internal organs, except for lungs and kidneys (Table 4, 88d). In conjoined twins with a single head with underdevelopment of cranium bones and exposured cerebral hemispheres (encephalocele) (Figure 8) the upper sheath of the beak was considerably shorter than the lower one (Figure 9).

Figure 7. Conjoined twins of emu from the single-yolked egg

Figure 8. Externalized brain of conjoined twins of emu

Figure 9. Asymmetrically reduced upper mandible of conjoined

The twins of the ostrich developed in the egg with single yolk (Figure 10). The embryos, directed abdominally towards the yolk sack conjoining them, differed in body weight and underdevelopment degree (Table 3, 50S). In the smaller of the twins, a deformed cranium (asymmetrical head) was found as well as one eye-left, (cyclopia) (Figure 11), bend vertebral column and subcutaneous swellings on the limbs (Figure 12). In its internal organs, lesions with haemorrhages were visible, and the hard liver lacked a division into lobes. The second twin was larger, normally developed, without body swellings and deformations. The malformations were only found in the liver, the tissue of which was very compact and hard.

Figure 10. Ostrich twins in the single-yolk egg

Figure 11. Skull abnormalities with cyclopia of one of ostrich

Figure 12. Bend vertebral column and swellings on limbs

Basing on the performed analyses one can not preclude that the reason of embryo deaths could be also exogenous infections of eggs assigned for hatching. It was found that despite all efforts made to comply with egg collecting hygiene, egg storage and their incubation, microbial infections could have happened. Two such cases took place in the present study (Table 3, 14S and Table 4, 87d). On the basis of embryo investigation, it was found that most probably they developed normally until the infection, as they were full-fledged and without any external deformations. Only an ostrich embryo failed to absorb a small part of the yolk sack into its body. During its dissection, only congestion of internal organs was observed as well as necrotic foci in the liver parenchyma giving it a marbled appearance, which could point to bacterial infection. An intensive smell of mycelium precluded taking the measurements of particular internal organs of the embryo. In both cases, microbiological investigation was not made.


It was found in the own studies that most embryos of both species had died mostly in the final stage of embryogenesis. High mortality rate of ostrich and emu embryos in last 7-14 days of incubation has been already observed [4, 9, 12, 23, 25].

During the embryogenesis in the majority of poultry species, two peaks of embryo deaths occur, the first in the beginning and the second at the end of incubation [3, 17]. In the studies of Szczerbińska [25], two peaks of embryo deaths were found in the emu, the first until 15th-16th day of incubation, and the second in the last several days of hatching. Similarly, two peaks of embryo deaths in case of the emu were distinguished by Deeming [8] and Horbańczuk [9]. According to these authors, the first critical period and increased embryo deaths fall to 6th-7th day, whereas the second one to 35th-36th day of incubation.

In the own studies, one of the causes of embryo deaths in birds in the last days of embryogenesis was their inappropriate positioning. The most frequently observed malposition of ostrich embryo is its head in the sharp end of egg [8, 9, 20]. As Brown et al. [5] states, out of those embryos, the position of which could be determined in the egg, 55% were malpositioned. Most common positions of these were: legs facing the air chamber in the correct position but the head facing the opposite pole, rump to the air chamber or chicks on their sides with legs along the equator and the head facing either the air cell opposite the pole. In the own studies among defective positions of embryos the mortality was stated when the head of emu embryo was in the sharp end of egg, whereas in case of ostrich embryo its head was in the equatorial part of egg with the beak directed towards left leg, both embryos lacking the possibility to respire with the air contained in the air chamber. One of the reasons of embryo abnormal positioning in the egg, apart from hereditary factors and the age and improper feeding of parental flock (nutrional deficiencies, especially of vitamins A and B12), are errors in artificial hatching technique [5, 19]. Wilson [27] found that the percentage of embryos taking defective positions in eggs is affected by: eggs being set with the small end up or in the horizontal position, inadequate or improper turning, high or low incubator temperature, high humidity, round-shaped eggs or very large eggs, retarded development and eggs handled or stored improperly. Inadequate thermal and humidity conditions, causing too small weight losses of incubated eggs (below 10%), may cause abnormal positioning of emu embryos. Horbańczuk [9], when incubating ostrich eggs with large humidity in the hatching chamber (40%), showed that the percentage of malpositioned embryos was the highest, while improper positioning of embryo, limiting or simply blocking its movements, affected negatively hatching indices.

The own studies proved that in the late died emu and ostrich embryos, hallmarks of prolonged hatching and slowed down metabolism were visible as well as problems with absorbing yolk sacks, caused by disturbances in water evaporation from eggs, which lead to their considerable watering. The greenish colour of the yolk sack, as is given by Borzemska [3], shows the beginning of yolk digestion and the secretion of bile and digestive juices. Moreover, in such eggs was much unused jelly-like matter, whereas haemorrhages were visible on the embryo organs. One of the reasons of the foregoing anatomicopathological lesions in embryos, according to the cited author, is under-heating of eggs over a longer part of incubation period.

Next problem in egg incubation, in particular in the ostrich, were the swellings of subcutaneous tissues (oedema), which were also noticed by Davis and Ackerman [7], Brown et al. [5], Horbańczuk [9] and Szczerbińska [25] in case of the emu. According to Sahan [23], the oedema did not occur only in 16 of 72 embryos (22.2%). The author gives the oedema as one of the main reasons of embryo deaths in the ostrich. Slightly lower percentage of swollen ostrich embryos presented Brown et al. [5] – only 15 out of 111 (14%), and Szczerbińska [25] – 6 of 41 died emu embryos (14.6%).

During the own observations in a group of embryos with developmental malformations, the occurrence of disturbances was found manifesting in head deformation, lack of cranial covers, exposure of cerebral haemispheres and beak underdevelopment and deformation. The similar head deformations were described by Rockwell et al. [22]. These anomalies are most frequently of genetic background, on the other hand they may however be also a result of improper feeding of parental flocks [22, 27]. In hens, with deficiency of mineral components such as manganese or molybdenum, hatches an increased percentage of invalid chicks, whereas embryos which had died mainly during the hatching and shortly before leaving the egg shell presented developmental malformations of limbs and disturbances in head development, no beak or its deformations [3].

In the emu and ostrich embryos that had died at the end of incubation occurred also non-physiological neck twisting and flattened or deformed head, which can be affected, apart from conditioning of genetic nature, by deficiency of folic acid in the feed as well as by overdosing of some medication, in particular of sulphonamides [3, 27]. In case of the flocks, from which the eggs originated, pharmacological remedies were not used, therefore the symptoms point more to a genetic background. According to Borzemska [3], in the hen embryogenesis such anomalies, apart from the size of limb pairs, occur mainly against the background of genetic conditioning, rarely as a result of egg over-heating. It should not be forgotten however that symptoms similar to the effect of action of lethal or semi-lethal genes may also result from improper feeding of laying birds, e.g. from deficiency of zinc, which makes drawing correct conclusions complicated.

Embryo dying may be also induced by exogenous infection of eggs assigned for hatching, into which the spores of toxigenic fungi penetrated through egg shell pores causing embryo deaths. In the own studies such egg infections occurred twice. It is known that frequent infection of eggs is found in the ostrich and the rhea [5, 6, 15, 21]. In the own studies the fungi proliferated on the external shell membrane in the air chamber region, where depositions of spreading mycelium had been visible. The embryos were dying in result of poisoning with fungi metabolites. Their integuments were mostly congested and amniotic fluid dark with intensive mycelium scent, which frequently made further analysis impossible.

Bird twins coming from single- or double-yolk eggs are still considered a nature phenomenon. Stockard [24] attributed polyembryony in birds to interruption of development before the completion of gastrulation. The occurrence of bird twins belongs to rarities. Olsen and Haynes [18] described three cases of twins out of 1153 eggs of the domestic fowl, whereas Kear [13] single case out of 833 eggs of the Muscovy duck. Batt et al. [2] pointed at the occurrence of five pairs of twins in the mallard and the Giant Canadian goose. Four of the pairs were normal twins, while one pair was joined at the head and neck regions. In each case the embryos shared the same yolk sac.

Reports on cases of the occurrence of bird twins have become increasingly frequent [8, 10, 11] since their first description made by Waddington [26]. Very little informations about avian conjoinet twins are publish.

Many developmental abnormalities leading to emu and ostrich embryo deaths may be connected with improper conditions of bird maintenance, their mating, as well as egg incubation. Despite a considerable progress in that field, losses caused by the scarcity of information concerning the reproduction use of these birds still continuously increase the costs of their production.

The study described in this paper showed that mortality of embryos and anomalies applied only to beak malformations occurring during their development were similar in both bird species.


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Monika Wiercińska
Department of Poultry and Ornamental Brids Breeding,
West Pomeranian University of Technology in Szczecin, Poland
Doktora Judyma 24, 71-466 Szczecin, Poland
email: m.wiercinska@interia.pl

Danuta Szczerbińska
Department of Poultry and Ornamental Brids Breeding,
West Pomeranian University of Technology in Szczecin, Poland
20 Doktora Judyma St.
71-466 Szczecin, Poland

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