The Egg Story

What do we know?EGGS CHICKENS

Vocabulary – PICK 15 AND DEFINE

lay brood fowl class hatch embryo poultry breed pip egg tooth rooster variety egg development

chicken bantam beak fertilized hen comb yolk chick down shanks white Nest feathers wattles Shell clutch wings

Activities – pick one with a partner and completeUsing the

vocabulary you just learned, make a collage with pictures you find in magazines or the internet to describe the words.

Using the vocabulary you just learned, write a song, poem or rap

IncubationEggs have been incubated by artificial

means for thousands of years. Both the Chinese and the Egyptians are credited with originating artificial incubation procedures. The Chinese developed a method in which they burned charcoal to supply the heat. They also used the hot-bed method in which decomposing manure furnished the heat. The Egyptians constructed large brick incubators which they heated with fires right in the rooms where the eggs were incubated.

Incubation continued…Over the years incubators have been refined

and developed to the point where they are almost completely automatic. The greatest development has occurred in the 20th century.

Modern commercial incubators are heated by electricity, have automatic egg turning devices, and are equipped with automatic controls to maintain the proper levels of heat, humidity, and air exchange. Present-day commercial incubators vary in capacity from a few thousand to many thousands of eggs, and they have made possible the development of modern hatcheries which produce almost 100 percent of all the chickens grown in this country.

What is an egg? vocabularyShell porousmembranesair cellalbumenvitelline membraneyolkgerminal disc or blastodermchalaza

What is an egg?Once you draw and

label the above drawing in your

notes, please go to the following

website: www.aeb.org

and click on the egg industry link, watch the following videos:

-The Egg- The Hen-Egg Farm

-Egg Processing

Also be sure to take notes during each

video!

Reproductive tract of a henThe egg is formed by a reproductive systemcomposed of an ovary and an oviduct.An ovary looks like a cluster of grapes andmay contain up to 4,000 small eggs or ova(singular ovum) which can develop into yolks.Each ovum is attached to the ovary by a thinmembrane sac or follicle.The oviduct is a large, coiled tube located inthe left side of the hen’s abdomen. In thisoviduct all parts of the egg, except the yolk,are formed.It is divided into 5 distinct regions:- infundibulum- magnum- isthmus- uterus- vagina

Chick development

Chick Development

DAY 1 18 hours – the digestive system

starts to appear 20 hours – the vertebral column

starts to appear 21 hours – the nervous system and

brain begin to form 22 hours – the head begins to form 23 hours – the extraembryonic

blood systems begin to form 24 hours – the eyes begin to form

DAY 2 25 hours – the heart begins

to form 35 hours – the ear pits begin

to form 37 hours – the amnion starts

to appear 42 hours – the heart starts to

beat 46 hours – the throat begins

to form

Extra Embryonic Blood System

The yolk sac surrounds the yolk and draws food from it for the embryo. The amnion is a

transparent sac filled with a colorless fluid in which the embryo floats that protects it from shocks

and prevents it from drying out. Respiration is made possible by the allantois. As it grows with the chick, the allantois

is pressed against the egg shell where it can easily absorb oxygen passing through the pores of

the egg shell in exchange for carbon dioxide. The allantois also stores waste, absorbs albumen

used as food by the embryo and absorbs calcium from the shell for bone construction. For the first

10 days the chick can absorb a sufficient amount of calcium from the yolk but as the formation of bones

begins to accelerate the chick must take calcium from the egg shell. There are two distinct extraembryonic blood systems: Blood vessels in the allantois called allantoic vessels which bring oxygen to the embryo and take carbon dioxide

away. The other blood system made of vitelline vessels brings nutrients from the yolk to the

embryo. During the first 3 days of its life, the chick relies on the vitelline vessels to also absorb oxygen but by

the 4th day the chick needs more oxygen than can be supplied by only the vitelline system and

begins to rely on the allantois which will soon take over respiration.

Heart and Circulatory System

• average body temp. is 98.6 F•4 chambers • cardiac muscle• valves

• higher metabolic rate• average body temp. is 106 – 113 F•Pulse rate 400 beats/minute•Smoother chambers of the heart

Chick Development

DAY 3 50 hours – the amnion

begins to form 60 hours – the nose

begins to form 62 hours – the legs start

to appear 64 hours – the wings start

to appear 70 hours – the allantois

begins to form

Day 4•The tongue begins to form•The tail appears•The toes begin to form•Extra-embryonic circulation is fully functional

DAY 5- The crop begins to form- The bones of the legs begin to form- The sex of the chick is determined and itsreproductive organs begin to form(ovary & oviduct for the female as studiedin Part III)

Chick Development

Day 6The beak and egg-tooth

begin to formThe ribs start to appearThe gizzard begins to formVoluntary movement

begins

Day 7The wings bend at the

elbowand the leg at the kneeThe toes are visibleThe abdomen is bigger as the intestine starts to loop

Chick Development

Day 8The feathers begin to formThe eye lids begins to form

Day 9The mouth opening

appearsThe claws begin to

form

Chick Development

Day 10 The beak starts to

harden The comb is visible The flight feathers

develop

Day 11 The toe claws begin to

curve downwards The bottom of the feet

become padded The chick begins to take

calcium from the eggshell

Chick Development Day 12 Scales appear on the

lower legs The chick continues to

grow and move

Day 13 Body fairly well covered

with feathers The left and right collar

bones join to form the wishbone

Chick Development Day 14 The embryo turns its

head towards the large end of the egg The skull and ribs have

begun to ossify

Day 15 The scales, claws and

beak are becoming firm

Bones and the skeleton Bones are made of minerals,

mostly calcium and phosphate. There are 3 types of bone cells: osteoblasts, osteocytes and osteoclasts.

Osteoblasts are responsible for making the structure and then laying in the minerals.

Osteocytes are responsible for feeding the bone and osteoclasts help shape the bones as they grow.

New bone is first created randomly and then reshaped in concentric layers like the rings of a tree. Bone can be either compact or spongy.

Compact bone on the outside provides strength, support and protection.

Spongy bone on the inside allow the bone to be lightweight and provide a space in which bone marrow can grow.

Bone marrow makes blood cells.

Bones and the skeletonWhat is cartilage?

Cartilage is a strong but flexible material like hard rubber. In the embryo, most of the skeleton is first made of cartilage. As the embryo grows, the cartilage is replaced by bone. This is called ossification.

How are bones different in birds?Bird bones contain air sacs and are said to be

pneumatized. When a bird takes off for flight the exaggerated movement of the wings creates an air current which fills the air sacs within the bones and makes the bird light enough to fly. The bones do not become pneumatized until after the bird hatches.

Chick DevelopmentDay 16The chick is fully

covered with feathersThe albumen is nearly

gone and the yolk is increasingly important

as nourishment

Day 17The chick turns its

beak towards the air cell

and begins preparation for hatching

Chick DevelopmentDay 18The growth of the

embryo is nearly complete

The amnion which protects the chick

begins to disappear

Day 19The yolk sac begins to

enter the bodyThe chick occupies all

the space in the eggexcept the air cell

Respiratory SystemThe lungs are not used forrespiration until just before thechick hatches. In the meantimewe have seen that the chick usesthe allantois to breathe.The amount of oxygen suppliedthrough the egg shell is enoughuntil the chick starts theexhausting process of hatching.During incubation, the waterwhich evaporates from the egg isreplaced by air which is stored inthe air cell. By the time the chickbegins to hatch, the air cell hasgrown to fill about 25% of theegg.

The chick’s first hatching movements are to break the shell membranes covering the air cell and take its first breaths with its lungs. The oxygen stored in the air cell is enough to allow the chick to break through the eggshell.

How birds breathe

The bird’s lungs are relatively small in proportion to its body size compared to humans; they are only half the size.

Human lungs are made up of millions of tiny balloons called alveoli which expand and contract as we breathe.

A bird’s lungs are not elastic, they do not change in size when the bird breathes.

Specialized elastic structures called air sacs are connected to the lungs and draw air through the lungs.

As air passes through the lungs oxygen in the air is exchanged for carbon dioxide in the blood.

How Birds Breathe Birds have two sets of air sacs: - caudal air sacs - cranial air sacs The caudal air sacs include the abdominal and the caudal thoracic

air sacs. The cranial air sacs include the cervical, clavicular and the cranial

thoracic air sacs. As we know air sacs even extend into the bones. Air sacs inflate or deflate

when the size of the bird’s chest changes. The bird controls this by moving its muscles. The largest of the air sacs, the abdominal air sac surrounds the abdominal organs and is largely responsible for breathing while the bird is at rest.

As a bird becomes more active, it needs more oxygen. Increased movement forces its chest to expand and compress more which in turn inflates and deflates more of its air sacs. This forces more air through the lungs and makes the bird less dense. When a bird flies all its air sacs are filled including those in its bones and makes it light enough to fly.

A bird can also use its air sacs to sing by forcing air through its vocal organs like a bagpipe.

Some birds can sing while they fly because they are able to sing when they breathe in as well as breathe out.

Constant airflow supplies birds with more oxygen than humans. This is necessary to maintain their high metabolic rate and for flying.

The lungs of the chick begin to form early to be ready when it hatches. Air sacs continue to develop long after the chick has hatched.

Chick DevelopmentDay 20The yolk sac is

completely drawn into the body

The beak breaks through the inner shell membrane

The lungs begin to function and to use the air cell for breathing

The allantois ceases to function and starts to dry up

Day 21The neck begins to

jerkThe egg tooth pips

through the shellThe chick hatches!

How the chick hatchesUsing its egg tooth (a tiny sharp horn on the top of its

beak) the chick pecks at the shell thousands of times. Finally it pips through the shell and begins to breathe air directly from the outside. After it has made a hole in the shell, the chick stops piping for a few hours and rests while its lungs are getting used to the outside atmosphere.

There is a high level of carbon dioxide in the egg compared with the outside environment. This actually causes the neck muscles of the chick to jerk and allow him to peck through the eggshell.

After resting the chick continues to pip by beginning to turn slowly inside the egg. As it turns, usually counter-clockwise, the egg tooth continues to ship away. In about 5 hours, the chick has made about three quarters of a turn inside the egg.

As the chick moves around the shell it begins pushing on the egg cap. Squirming and struggling the chick pushes the cap for about one hour. Finally it breaks free from the shell,still wet and panting.

How the chick hatchesWhen the chick is

completely out of the shell it lies still.

It is extremely tired. After a rest it begins to rise to its feet and gain coordination.

Within a few days the egg tooth will disappear.

Common Breeds of ChickenAnconaAraucanaAustralorpBrahmaBantamCampineCochinFrizzleHoudanLeghornMinorcaNew Hampshire Red

OrpingtonPlymouth RockPolishRhode Island RedRosecombSicilian ButtercupSilkieSultanSumatraSussexTransylvanian Naked

NeckWyandotte