Incubation and Embryology of the Chicken Flashcards
What does the nucleus look like?
A small, white or light-colored speck.
How big is the nucleus?
About the size of a pin head (2-3 mm diameter).
Where is the nucleus located?
Top side of the yolk.
What does the male sperm cell find before fertilization?
The lodgment.
What is a fertilized egg characterized by?
A white ring on the yolk surface.
How large is the ring on a fertilized egg?
3-4 mm in size.
What temperature should fertile eggs be stored at?
54-59 F.
*Should maintain a constant weight.
What do temperatures above 77 F cause?
Cellular replication of the germ cell on the yolk of the fertile egg, increasing embryonic mortality and reducing hatchability.
What do temperatures below 50 F cause?
Inactivation of the germ cell.
What humidity should fertile eggs be stored at?
75%.
When storing fertile eggs, which side should be facing downward?
The small end.
When is optimal hatchability achieved in eggs?
When they are less than 10 days old.
When is reasonable hatchability obtainable in eggs?
Up to 14 days of age.
What are the 4 principles of artificial incubation of fertile eggs?
- Correct and even temperature controlled by a thermometer or thermocouple.
- Correct humidity controlled by ventilation rate and water application.
- Turning of the fertile egg approximately 90 degrees several times per day (manual or automatic).
- Correct O2 and CO2 concentrations controlled by ventilation.
What temperature is required for incubation?
99-102 F w/ a +/- 2 variation before significant embryonic mortality.
At what 2 stages are embryos most susceptible to temperature variation?
- Early phase.
- Late phase.
What is placed on the eggs to aid in maintaining humidity?
Water via water sprayers.
What is the humidity range that embryos can survive in?
40%-90%, below or above this range is when negative consequences occur.
What humidity is good hatchability achieved at?
50-65%.
*Three days before hatching, this increases to 70-90% humidity.
Why is egg rotation/turning done?
- To ensure that the developing embryo on the yolk does not adhere to the shell membrane.
- To allow the embryo to slide in the inner white and access additional nutrients for embryonic development.
When does adherence to the shell membrane occur?
- During fertile egg storage.
- During early incubation (first week).
Why is it better to rotate/turn the egg an uneven number of times?
So that the egg is not in the same position for an extended period of time.
What concentration of CO2 is optimal for chick growth?
0.4%.
Above what concentration is CO2 detrimental to chick growth?
1%.
What are the concentrations of O2 and CO2 in a normal atmosphere?
- 21%.
- 0.04%.
When is ventilation rate and CO2 concentration most critical for chicks?
Late phase of incubation.
*Implied by hatched chicks being susceptible to O2 deviation.
When is the earliest eggs can be candled?
5-8 days of incubation.
*At 18 days to see line between embryo and air cell.
Why are eggs candled?
To examine the embryo for blood vessel development and a dark spot.
What does an infertile egg look like when candled?
It is clear and there is no evidence of blood.
What does early embryonic death look like when the egg is candled?
A blood ring surrounding the yolk.
What is the incubation time for ducks?
28 days.
What is the incubation time for geese?
28-32 days.
What is the incubation time for turkeys?
28 days.
What is the incubation time for guinea fowl?
27 days.
What is the incubation time for pheasant?
24 days.
What is the incubation time for quail?
23-24 days.
What is the incubation time for chicken?
21 days.
What happens to the egg as the embryo grows?
The egg will progressively dry-out.
What is the ideal % weight loss for an egg?
13%.
What does too high of an incubation temperature cause?
- Early hatching.
- Weak chick.
- Unhealed navels.
- Unabsorbed yolk sac.
- Crooked toes.
- Crossed beaks.
- A high proportion late dead in shell.
What does too low of an incubation temperature cause?
- Late hatching.
- Large chicks.
- Soft chicks.
- Slow starting.
- Wry neck.
What does too high of a humidity cause?
- Large number unhatched.
- Large number un-pipped.
- Large number live trapped embryos
- Large chicks coated with albumen.
What does too low of a humidity cause?
- Small chick.
- Weak chick.
- Exhausted chicks in mostly chipped shells.
- Chicks glued to shell.
- Large air cell.
What is embryology of chickens?
The study of the development of the chicken inside the egg.
When does fertilization take place?
15 minutes after the yolk has been released.
When does cell division to create the new embryo occur?
5 hours after fertilization and continues as the egg passes along the oviduct and after the egg is laid.
How long does development take?
22 days, 1 day in the oviduct and 21 days in the incubator or nest.
What is formed when the sperm and egg meet?
The zygote (A single cell with the complete number of chromosome).
What is the zygote called by the time is leaves the isthmus?
The blastoderm or embryo.
*Eight cells.
How many cells comprise the blastoderm once it has reached the uterus?
256 cells, 4 hours later.
What two layers does the initial dividing layer form?
- Ectoderm.
- Endoderm.
*Mesoderm forms later.
What happens at around the same time the ectoderm and endoderm are formed?
The central cells of the blastoderm separate from their contact with the yolk to form a cavity where embryo development will occur.
What organs and tissues develop from the ectoderm?
- Nervous system.
- Parts of the eye.
- Feathers.
- Claws.
- Beak.
- Skin.
What organs and tissues develop from the endoderm?
- Respiratory system.
- Digestive system.
- Secretory organs.
What organs and tissues develop from the mesoderm?
- Muscle.
- Skeleton.
- Circulatory system.
- Reproductive organs.
- Excretory system.
What happens when the temperature of the egg drops below 68 F?
The embryo becomes dormant and most development stops.
*Called physiological zero
What happens with each rise and fall above/below 68 F?
The embryo gets progressively weaker.
Why do extra embryonic membranes form in the egg?
The avian embryo has no anatomical connection to the hen, meaning all nutrition must be contained in the egg. These membranes help with accessing the nutrients and carrying out essential processes.
What are the 4 extraembryonic membranes?
- Yolk sac.
- Amnion.
- Allantois.
- Chorion.
What is the yolk sac?
A membrane that envelops the yolk.
What is the function of the yolk sac?
To produce an enzyme that changes the yolk material into a useable form.
What happens to unused yolk material?
It is drawn into the abdomen and used during the first 2-3 days post-hatch while the chick learns how to eat/drink and where to find food/water.
*Also used during transport.
What is the amnion?
A sac filled with fluid that the embryo floats in.
What is the function of the amnion?
Acts as a shock-absorber in which the fragile embryo can develop.
What is the allantois?
An extensive circulatory system connected to the embryo.
*Completely surrounds the embryo when fully developed.
What is the allantois driven by?
The embryonic heart.
What three broad functions does the allantois play a role in?
- Respiratory.
- Excretory.
- Digestive.
What is the respiratory role of the allantois?
Oxygenates the blood and eliminates carbon dioxide.
What is the excretory role of the allantois?
Removal of metabolic waste and deposition of it in the allantoic cavity.
What is the digestive role of the allantois?
Allows for access to the albumen and the calcium of the shell.
What is the chorion?
An extra-embryonic membrane that fuses the inner shell membrane to the allantois.
What is the function of the chorion?
To help the allantois carry out its functions.
What does knowing what each day of embryonic development looks like allow for?
Determination of at what age/stage the embryo may have died.
What is the normal hatching position of a chick?
- Legs up under the head.
- Head under the right wing.
- Forepart of the body towards the large end of the egg.
How is it possible that eggs laid days apart hatch within hours of one another?
The embryos send out a series of clicks to one another in order to synchronize hatching.
*Why it is important to keep hatching trays in contact with each other in hatching facilities.
