PROCESS OF EGG FORMATION IN POULTYRY


PROCESS OF EGG FORMATION IN POULTRY


The process of egg formation ic controlled by hormones. The egg is formed partly in the ovary and partly in the oviduct.
The egg is formed in the reproductive tract of a female chicken, called a hen. The reproductive tract is divided into two major parts: the ovary and the oviduct. The ovary is where the yolk is added. When the yolk reaches the right size, it is released from the ovary by a process called ovulation. The released yolk is then picked up by the infundibulum. It is here that fertilization must take place.The yolk then passes to the magnum, where the albumen is added. It then goes on to the isthmus for the addition of the shell membranes

Ovary:

The yolk is secreted by the ovary and enclosed in a follicle. The yolk increases iin size by accumulating yolk materials carried from different parts of the body by blood stream. The germinal disc is attached to the top of the yolk. The follicle burst to release the yolk.




Infundibulum:

The yolk released by the ovary is taken up by the infundibulum, the internal terminam part of the oviduct. Fertilization of the egg occurs in this part of the oviduct, before the other components are added. However, complete formation of the egg is independent of whether the egg is fertilized or not. The egg spends 15minutes in the infudibulum before it moves to the magnum.

Magnum:

In the magnum, the egg stays for three hours and part of the albumen is secreted on the yolk. Chalaza is also formed in this region. The egg now moves to the isthmus.
Isthmus: The egg stays here for 75minutes and the two shell membranes are formed. The shape of the egg is also formed at this region after which it moves to the uterus.
Uterus: The egg stays here for 19 – 20 hours where the shell is formed from calcium carbonate secreted by glands of the uterus. Mineral solutions are also added to the egg after which it moves to the vagina.

Vagina:

The egg stays here for a very short time before it is laid through the cloaca or vent. It takes almost 26hours for a complete egg to be formed and laid.





MEMBRANE:

Immediately after the outer shell are outer and inner membranes. Both membranes give protection to the egg.

Airspace:

The airspace is located on one of the pointed ends of the egg. It is found in-between the outer and inner membranes. The airspace is very important for respiration of the embryo.

Albumen:

This is also called the egg white. It accounts for over 50% of the total body weight of the egg. It is rich on protein
Yolk: This is located at then centre of the egg. It is a yellowish jelly0like mass. It is rich in proteins, mineral salts, vitamins and other food substances. It supplies the embryo nutrients.


Embryo:

This is also called germinal disc. This is located at the centre of the yolk as a dark spot. The germinal disc is only found in fertile eggs. It develops to form the chick during incubation period.
Chalaza: The chalaza extends to both sides of the yolk. It is a piece of thick protoplasm. It holds the yolk and the embryo in place within the albumen.

How a Hen Makes an Egg

The egg is formed in the reproductive tract of a female chicken, called a hen. The reproductive tract is divided into two major parts: the ovary and the oviduct. The ovary is where the yolk is added. When the yolk reaches the right size, it is released from the ovary by a process called ovulation. The released yolk is then picked up by the infundibulum. It is here that fertilization must take place.The yolk then passes to the magnum, where the albumen is added. It then goes on to the isthmus for the addition of the shell membranes. The developing egg spends most of its time in the shell gland, where the shell and any shell pigments are added. As the egg is being assembled it travels down the oviduct small end first. In the vagina it is pushed out the large end first. This prevents the egg from being contaminated by fecal material when it is laid.

Formation of the egg

Figure 1: Reproductive organs of the hen
Figure 1:
Reproductive organs of the hen

The egg is formed gradually over a period of about 25 hours. Many organs and systems help to convert raw materials from the food eaten by the hen into the various substances that become part of the egg.
The ovary

The hen, unlike most animals, has only one functional ovary - the left one - situated in the body cavity near the backbone. At the time of hatching, the female chick has up to 4000 tiny ova (reproductive cells), from some of which full-sized yolks may develop when the hen matures. Each yolk (ovum) is enclosed in a thin-walled sac, or follicle, attached to the ovary. This sac is richly supplied with blood.
The oviduct




The mature yolk is released when the sac ruptures, and is received by the funnel of the left oviduct (the right oviduct is not functional). The left oviduct is a coiled or folded tube about 80 cm in length. It is divided into five distinct sections, each with a specific function, as summarised in table 1.

Functions of various different sections of the hen's oviduct
the yolk
Section of oviduct Approximate time egg spends in this section Functions of section of oviduct
1 Funnel (infundibulum) 15 minutes Receives yolk from ovary. If live sperm present, fertilisation occurs here (commercially produced table eggs are not fertilised)
2 Magnum 3 hours Albumen (white) is secreted and layered around
3 Isthmus 1 hour Inner and outer shell membranes are added, as are some water and mineral salts
4 Shell gland (uterus) 21 hours Initially some water is added, making the outer
white thinner. Then the shell material (mainly
calcium carbonate) is added. Pigments may also
be added to make the shell brown
5 Vagina/cloaca less than 1 minute The egg passes through this section before
laying. It has no other known function in the
egg’s formation

HERE YOU WILL FIND EVERY AVAILABLE TOPICS ABOUT AGRICULTURAL SCIENCE AND BIOLOGY. AND THE LINKS TO THEIR VARIOUS SOURCES.
1. DEVELOPMENT OF AGRICULTURE
2. IMPORTANCE OF AGRICULTURE
3. SUBSISTENCE AGRICULTURE
4. COMMERCIAL AGRICULTURE
5. PROBLEM OF AGRICULTURAL DEVELOPMENT
6. SOLUTIONS TO POOR AGRICULTURAL DEVELOPMENT
7. AGRICULTURAL LAWS AND REFORMS
8. ROLES OF GOVERNMENT IN AGRICULTURAL DEVELOPMENT
9. AGRICULTURAL POLICIES
10. PROGRAM PLANNING IN AGRICULTURE
34.
FORESTRY
35. WILDLIFE CONSERVATION
36. FACTORS AFFECTING LAND AVAILABILITY
37. TOPOGRAPHY
38. SOIL
39. BIOLOGICAL FACTORS
40. SOCIAL-ECONOMIC FACTORS
41. ENVIRONMENTAL FACTORS AFFECTING AGRICULTURAL PRODUCTION
42. CLIMATIC FACTORS AFFECTING AGRICULTURAL PRODUCTION
43. TEMPERATURE
44. RAINFALL
45. WIND
46. SUNLIGHT
47. SOLAR RADIATION
48. BIOTIC FACTOR AND AGRICULTURAL PRODUCTION
49. PESTS
50. BIRDS
51. DISEASES
52. SOIL MICRO-ORGANISMS
53. SOIL PH
54. ROCK FORMATION
55. IGNEOUS ROCK
56. SEDIMENTARY ROCKS
57. METAMORPHIC
58. SOIL AND ITS FORMATION
59. FACTORS OF SOIL FORMATION
60. LIVING ORGANISM
61. PARENT MATERIALS
62. SOIL FORMATION TOPOGRAPHY
63. PROCESS OF SOIL FORMATION
64. WEATHERING
65. PHYSICAL WEATHERING
66. CHEMICAL WEATHERING
67. PRESSURE
68. WATER
73. BIOLOGICAL WEATHERING
74. CHEMICAL AND BIOLOGICAL COMPOSITION OF THE SOIL
75. SOIL WATER
76. MICRO AND MACRO NUTRIENTS
77. SOIL MICRO ORGANISM
78. PROPERTIES OF SOIL
79. SOIL STRUCTURE
80. SANDY SOIL
81. CLAY SOIL
82. LOAMY SOIL

83. SOIL TEXTURE
84. IDENTIFICATION OF SOIL TYPES THROUGH EXPERIMENTS
85. RETENTION OF WATER BY VARIOUS SOIL TYPES
86. DETERMINATION OF SOIL PH REACTION
87. COLORIMETRIC DETERMINATION OF SOIL PH LEVEL
88. PH SOIL TEST
89. PLANT NUTRIENTS
90.
MACRO NUTRIENTS IN GENERAL
112.
THE MAINTENANCE OF SOIL FERTILITY
113. CROP ROTATION
114. APPLICATION OF ORGANIC MANURES
115. FARM YARD MANURE
116. APPLICATION OF INORGANIC MANURE

117. LIMING
118. FARMING PRACTICES
119. BUSH BURNING
120. CLEARING

121. FERTILIZER APPLICATION
122. ORGANIC MANURING
123. FARM YARD MANURE

124. HUMUS
125. COMPOST
126. CROP ROTATION
133. FARM POWER AND MACHINERY
134. SOURCES OF FARM POWER
135. HUMAN SOURCE
149.
PLOUGHS
142.
FIELD MACHINES
157.
PLANTERS
164.
SIMPLE FARM TOOLS
165. AGRICULTURAL MECHANIZATION
166. THE CONCEPT OF MECHANIZATION



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