Transcript The Avian Egg Structure, Production, Function

The Avian Egg
Structure, Production, Function
Topics
• Anatomy of the Egg
• Anatomy of Avian Female Reproductive
Tract
• Process of Egg Formation
• Aspects of Incubation and Hatching
• Dystocias
Egg Types
• Eight Basic Shapes
• Egg sizes range from
10 mm to 145 mm in
length
Egg Colors
• Multitude of colors, but all
formed from two pigments
derived from porphyrins
• Color and mottling serves
to camouflage the eggs in
the nest
• Cavity nesting birds have
colorless eggs
• Colors are added in the
uterus during shell
formation (below)
Anatomy of the Egg
Seven Components
•
•
•
•
•
Yolk
Albumin
Membranes
Chelazia
Chorioallantoic
Membrane
• Air Cell
• Shell
Anatomy of the Egg
Seven Components
•
•
•
•
•
Yolk
Albumin
Membranes
Chelazia
Chorioallantoic
Membrane
• Air Cell
• Shell
Yolk
• Formed in the liver,
transported to ovarian
follicle
• 33% lipid
• 19% protein
• 48% water
• Layed in concentric
layers
Albumin
• Four distinct layers
– Chalaziferous - inner
thick
– Inner thin layer
– Outer thick layer
– Outer thin layer
• Protects yolk from invasion
by microorganisms and
provides water, protein and
minerals to the embryo
Cross-section of Egg Shell
• Membranes
• Pores
• Gas Exchange
– Oxygen
– Carbon Dioxide
– 15% weight loss
during incubation
– Related to incubation
time (see tables)
Female Reproductive Tract
• Ovary Most female birds
have one functionally
ovary (on the left)
• Infundibulum - site of
fertilization
• Magnum - albumin
addition
• Isthmus - membranes
• Uterus - shell gland
• Vagina - transport to
exterior
• Sperm storage occurs at
various sites in tract in
some species
Cloacal Structure
Oviduct
Incubation Issues
• Temperature
– Regulates rate of development
– Tolerance for lowered temperature decreases as
embryo grows
– The incubation period (from laying to hatching) for
budgie and cockatiel eggs is 18 to 21 days,
respectively, whereas for the African grey parrots,
Amazon parrots, and macaws it is app. 26 days
• Humidity: regulates water loss
– Determined by internal egg temp (humidity is 100%)
and ambient humidity and gradient between the two
• Turning
Incubation Times
Species
Chicken
Cockatiel
SC Cockatoo
Peregrine
Bald Eagle
Philippine
Eagle
Time to Pip (d)
Time to Hatch(h)
20.5
21
28
29
34
56
6 – 12
24-48
24-28
36
24-30
30-45
Incubation Issues
• Turning
– Most critical from day 3 to day 7
– Required for:
• Proper incorporation of albumin into amnion
• Failure to incorporate leads to water loss from
albumin, increased viscosity and setttling between
chorioallantoic membrane and inner shell membrane
• This results in decreased oxygen diffusion
– Ideal turning rate:
• Minimum of 3x/d
• More than 24x/d is not necessary
Managing Water Loss by the 14 16 % Principle
• Weigh egg at time of lay
• Calculate projected weight at hatch by
subtracting 15-18% of weight
• Plot laid weight on day 1; and pip weight at
appropriate point for incubation time (e.g.
21 days)
• Connect with a straight line
• Weigh eggs periodically during incubation
Altering Weight Loss
• Too much loss:
– Place in incubator with higher humidity
– Cover part of the egg with white glue
• Too little loss:
– Place in incubator with lower humidity
– Thin part of the egg-shell by sandpapering
Appearance of Fertile Egg at Lay
and during Early Development
Stages of Embryonic
Development
Stages of Embryonic
Development
Assessing Eggs during
Incubation: Candling
• Blood Vessels of
Chorioallantoic layer
• Embryonic Position
Assessing Eggs during
Incubation: Candling
• Blood Vessels of
Chorioallantoic layer
• Embryonic Position
and Condition
Assessing Eggs during
Incubation: Radiology
• Embryonic Position
and Condition
Note head down
position
Hatching Process
• Membrane Drawdown - due to water-loss
• Air Cell Formation - initiation of airbreathing by developing chick
• Pipping
• Rotation - counterclock-wise
• Assisted Hatching - do not initiate until
chorioallantoic blood vessels shut down.
Appearance of Healthy Chick at
Hatch
• Color
• Hydration Status
Malpositions and Hatching
Problems
• Malpositions 1 - 6
– Head at small end of egg is most common
(mp2) - reduced hatchability
– Head under left wing (mp 3) - lethal
• Oversize Embryos
• Unretracted Yolk Sacs
Malpositions and Hatching
Problems
• Unretracted Yolk
Sacs
• Idiopathic
Malpositions and Hatching
Problems
• Malpositions 1 - 6
– Head at small end of
egg is most common
(mp2) - reduced
hatchability
– Head under left wing
(mp 3) - lethal
Malpositions and Hatching
Problems
• Oversized Embryos
Dystocias (Egg-Binding) and Other Problems
Internal Laying