Diagnosis of Incubation Problems due to Heredity, False Incubator Settings and Formaldheyde Poisoning.




Findings when candling the eggs


Findings on the embryos during incubation

Day old chicks appearance

Hereditary diseases

Greatly shortened legs, “Mole” foot, wingless, short-beak, Cyclops, encephalocele (cranium bifidum) , eyeless embryos

Aged egg

High mortality at the first days of incubation, lack of embryo growth and development, in terms of the allantois closing and the use of protein.

Irregular shape of the Germinal disc, that displays a foam-like surface

Delayed exodus, many weak day old chicks

 Overheating at the first days of incubation

Part of the batch have well-developed embryos

A lot of deformities of the head, eye and jaw Conclusion of the incubation cycle somewhat earlier.

 Overheating between 3d -5th day of incubation

Most embryos are well developed

Ectopic and deformed heart, stomach and liver

Conclusion of the incubation cycle somewhat earlier.

Short-term acute overheating


Sticking of the embryo to the undamaged shells in the dark blood vessels of the allantois.

Hyperemia and hemorrhage in the skin, liver, kidney, heart and brain, the head is positioned in the yolk

Prolonged overheating during the second half of incubation

Early projection of the beak and the neck of the embryo into the air chamber.

Unused protein at the opening of live embryos, cystic wall of the amnion and the allantois.

Many dead embryos, hatched from the shell but the yolk is not absorbed, irritated yolk sac, intestines, heart, and kidneys, thick intact protein, swelled neck with hemorrhage

Early but elongated hatching small sized and dirty day old chicks, with bleeding umbilical cord.


Under heating at the first half of incubation


Lack of growth and development, in terms of closing of the allantois and the use of protein

Lots of embryos die before hatching, with the following symptoms:

Stunted growth, sticking of the intact protein, to the egg shell. Egg is filled with liquid, mixed with blood; the intestines kidneys and liver are often congested. Neck swelling with hemorrhages.

Output is delayed, the bulk of day old chicks is of substandard quality and weak (defective spinal cord)

Under heating at the second half of incubation

On the 19th day of incubation many embryos are stunted

A lot of the embryos are alive in the egg shell but not hatched. They present the following signs:

Late atrophy of the allantois, swelling of the umbilical ring, rectum full of content from the bile, swelling with hemorrhages in the neck.

Exodus is delayed, a lot of substandard quality day old chicks (enlarged abdomen, swelling of the umbilical ring)

Under heating at the last 2-3 days of incubation

Many dead embryos at hatching with the following signs:

Swelling of the allantois the umbilical ring the neck, enlarged heart. A lot of live embryos pip the egg shell but they are not able to hatch.

Inadequate ventilation

Increased mortality

Hyperemia and hemorrhage of the skin and the internal organs.

Poison gases and vapors of formaldehyde

Great mortality during the first half of incubation, especially at the first 2-3 days

Wrong positioning of the embryo in the middle of the incubation. Congestion of the heart, liver & lungs, bleeding in the allantois, swelling of the neck with hemorrhage

High mortality rate, congestion and edema of the lungs

Excessive  humidity


Delayed closure of the allantois, increased mortality in the middle of the incubation before hatching. Stunting.

Sticking of the beak to the shell while piping.

The crop, the intestines and the stomach are filled with fluid, incorrect positioning of the embryo inside the egg,

swelling, bleeding of the neck,

Atrophy of the allantois.

Belated conclusion of the incubation cycle, big belly



Incubator humidity

Excessive weight loss of the eggs

The embryo is stuck in the middle of the egg. Bleeding of the allantois, undamaged egg shells dry and firm, dry fluff

Day old chicks small, thin and dry

Improper turning of the eggs

Sticking of the yolk to the egg shell, the allantois does not include protein

The protein remains outside the allantois, sometimes drawn into the abdominal cavity with the yolk


Michail J. Mavridis DVM




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