CHICK EMBRYO DEVELOPMENT

fertilization, zygote formation, cleavage, gastrulation, organogenesis, hatching

Stages of Embryonic Development

Sperm Storage Tubules of Utero-vaginal Junction

Primary Storage of Sperm

2-3 weeks

Timing of ovulation in the female does not always coincide with the time of insemination by the male.

Capacity for the sperm to reside: ____

Cloacal kiss

is referred to mating by cloaca

Zygote

When the sperm cell fertilizes the female egg cell it forms the __.

a single cell with the correct number of chromosomes

Cleavage (Cell Division)

The newly formed single cell begins to divide into 2, then 4, 8, 16, 32 and so on.

At the time of laying, hundreds of cells are grouped in a small, whitish spot (the blastoderm or germinal disc ) that is easily seen on the surface of the yolk.

When the egg is laid and cools, division of the cells ceases.

Isthmus; uterus

The first cleavage (4 cell division) occurs in

Further Cell division occurs in the

Stage X

the eggs will be laid containing 50 ,000 - 60 ,000 cells at __ embryonic growth .

physiological zero

To keep the embryo at Stage X, egg storage temperature should be maintained at

Stage XIII

Long -stored eggs are treated with SPIDES to further the embryonic growth not more than __ to make them stronger to withstand the storage .

Physiological Zero

Temperature below 22°C, the embryo becomes dormant and most development stops.

Temperature above 22°C, embryonic activity re-initiates

Gastrulation

(Germ Layer Formation)

Area Pellucida (Body of the Embyo)

the translucent central area of the blastoderm

Area Opaca (Extra-Embryonic Membranes)

the opaque area of the blastoderm

Extra-Embryonic Membranes (EEM)

the embryo develops special membranes external to its body to access the nutrients in the egg and to carry out essential bodily functions.

1. yolk sac, 2. amnion, 3. allantoin, and 4. chorion.

Four EEM

Yolk Sac

This sac envelops the yolk and produces an enzyme that changes the yolk material into a form that can be used as a food source by the developing embryo.

Amnion

The __ forms a sac that is filled with fluid in which the embryo floats.

Allantois

The __ develops an extensive circulatory system connected to the embryo and is driven by the new embryonic heart. When the allantois is fully developed it completely surrounds the embryo

functions:

Respiratory

Excretory

Digestive

Chorion

The __ fuses the inner shell membrane to the allantois and helps that membrane to carry out its functions

Hatching

-chick emergence

Development in the Oviduct

fertilization, zygote formation, cleavage

Development in Incubator

gastrulation, organogenesis, hatching

Differentiation Phase

Formation of different tissues that will develop into the chickens' final organs in the growth phase

Risk of malformations are high in this stage

Day 1

18 hours - appearance of alimentary tract

20 hours - appearance of vertebral column

21 hours - beginning of nervous system

22 hours - beginning of head

Appearance of tissue development

Day 2

The embryo has about 4 times as many cells as on day 1.

Developing blood vessels that will connect the embryo to the yolk, its source of food.

Appearance of embryonic tissue.

Day 3

Heart beats.

Blood vessels very visible.

The embryo has about 4-15 times as many cells as a day 2 embryo.

Day 4

Eye pigmented

The embryo has about 4-15 times as many cells as a day 2 embryo.

Day 5

Appearance of elbows Day 7 and knees.

At this stage it still look like a human embryo.

Day 6

Appearance of beak. Voluntary movements begin.

At this stage it still look like a human embryo.

Day 7

Comb growth begins. Egg tooth begins to appear.

At this stage it still look like a human embryo.

Growth Phase

Increasing size and mass of organs and embryo.

Higher incubation temperature increases growth rate and shortens incubation period.

Day 8

Feather tracts seen.

Upper and lower beak equal in length.

Day 9

Embryo starts to look bird-like.

Mouth opening occurs

Day 10

Egg tooth prominent.

Toe nails visible.

Day 11

Comb serrated.

Tail feathers apparent.

Day 12

Toes fully formed.

First few visible feathers.

Day 13

Appearance of scales.

Body covered lightly with feathers.

Day 14

Embryo turns head towards large end of egg.

Maturation Phase

Characterized by loss of tissue water

Organs become responsive to heat and cold stress

Growth rate of embryo decreases but temperature increases.

Day 15

Gut is drawn into abdominal cavity

Day 16

Feathers cover complete body. Albumen nearly gone.

Day 17

Amniotic fluid decreases. Head is between legs

Day 18

Growth of embryo nearly complete.

Yolk sac remains outside of embryo.

Head is under right wing.

death during this phase can be due to the transfer

Day 19

Yolk sac draws into body cavity.

Amniotic fluid gone.

Embryo occupies most of space within egg (not in the air cell).

Day 20

Yolk sac drawn completely into body.

Embryo becomes a chick (breathing air with its lungs).

Internal and external pipping occurs.

Day 21

The chick begins by pushing its beak through the air cell. The chick continues to push its head outward. The sharp horny structure on the upper beak (egg tooth) and the muscle on the back of the neck help cut the shell. The chick rests, changes position, and keeps cutting until its head falls free of the opened shell. It then kicks free of the bottom portion of the shell. The chick is exhausted and rests while the navel openings heal and its down dries.

Endothermic Phase

Embryo requires heat in order to develop. During this phase, insufficient heating, too slow temperature rise or interruption of the 'warm chain' can result in early embryonic deaths and impair the final incubation outcome.

Exothermic Phase

Embryo produces heat as a result of growth, and heat is needed to be dissipated. Eggs from peak flock ages (30-50 weeks) and some breeds with high growth potential release more heat than others and it should be taken into account during incubation.