Advanced Incubation and
Embryology
Ken Koelkebeck
U of I Extension Poultry Specialist
kkoelkeb@illinois.edu
The Life of a Chick
• Life begins with single cell formed by
joining of two parent cells: ovum
(yolk) and sperm = fertilization
• Fertilization occurs about 24 hours
before egg is laid
• After fertilization, single cell beings
to divide to 2, 4, 8, 16 cells and so on.
This occurs on germinal
disc/blastoderm
Chick Development
• Cells begin to divide into segments
during incubation
• 3 segments - ectoderm
- mesoderm
- endoderm
• Ectoderm – skin, feathers, beak,
claws, nervous system, eye, mouth
Chick Development
• Mesoderm – bone, muscle, blood,
reproductive and excretory tracts
• Endoderm – lining of digestive
tract, secretory, respiration organs
Chick Formation
• Extra-embryonic membranes of
importance
1)
2)
3)
4)
Yolk sac
Amnion
Chorion
Allantois
• Yolk sac – tissue layer growing
over the yolk – digests and absorb
yolk material
Chick Formation
Amnion
• Fluid filled sac that surrounds
embryo and serves as
protection
• Fluid allows embryo to move,
change position, and shape
• Fluid keeps embryo parts from
sticking together
Chick Formation
Chorion
• Serves to contain both amnion
and yolk sac
• No function at first, but then
joins with allantois to form
chorio-allantoic membrane
• Allows calcium reabsorption
through capillaries of allantois
from the shell
Chick Formation
Allantois
• Serves as respiratory organ for
embryo
• Holds excretions from embryo
• Absorbs albumen (nutrient
protein) for embryo
• Absorbs calcium from shell for
embryo
• Allantois origin within body of
embryo
Embryonic Blood Vessels
• One – vitelline vessels carry yolk
material to embryo
• Two – allantoic vessels –
respiration and waste material
Hatching
Days 19 & 20 - Abdominal wall surrounds
yolk sac
- Chick withdraws rest of yolk
into body
- Fluid decreases in amnion
Day 21
- Chick forces egg tooth
through air cell- head under
right wing takes first breath
– internal pipping – chick
peeping inside
Hatching
Day 21 - Egg tooth breaks through shell
– external pipping
• Process last from 4 to 12 hr
• Chick emerges very wet, tired and
rests for several hr
• After exiting shell, egg tooth
(beak) dries and falls off
Thank You