Chicken egg (broken)
Eggs and chicks

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Gallus gallus, chicken

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More about chicken at GeoChemBio

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cellular organisms - Eukaryota - Fungi/Metazoa group - Metazoa - Eumetazoa - Bilateria - Coelomata - Deuterostomia - Chordata - Craniata - Vertebrata - Gnathostomata - Teleostomi - Euteleostomi - Sarcopterygii - Tetrapoda - Amniota - Sauropsida - Sauria - Archosauria - Dinosauria - Saurischia - Theropoda - Coelurosauria - Aves - Neognathae - Galliformes - Phasianidae - Phasianinae - Gallus - Gallus gallus

Brief facts

Traits for selection of broilers (meat producing chicken)

In last decades, it is recognized that this intense selection has been accompanied by reduced reproductive efficiency, to the point that male fertility may potentially become a limiting factor for growth of the broiler industry in the near future (each 1% reduction in fertility costs industry millions of dollars annually). Continuing decrease in fertility might force producers to switch to artificial insemination. The precise causes of this fertility reduction have not been yet determined and can be quite complex, but recent studies isolated at least one of the components: large males may have more difficulties to achieve complete mating with successful sperm transfer into the female's oviduct.

Traits for selection of egg-laying chickens

Currently, egg-producing industry pays increased attention to earlier underappreciated behavioral traits such as cannibalism (severe pecking accompanied with consumption of the opponent's blood and tissues), feather pulling, and other aggressive tendencies; fearfulness.

Molting (feather dropping) is induced to cause ovarian arrest leading to a second cycle of egg laying. After a molt, livability and egg quality and quantity are improved compared with a non-molt control group. Feed deprivation for about 14 days has been adopted to induce molt because it is easiest method, which produces the best results. Typically chicken loose 25-30% of their body weight during the forced fasting. Many studies have been done to find alternative, less stressful methods to induce molt in egg-laying chickens.

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Courting rooster
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Developmental stages (life cycle)

Hamburger and Hamilton (1951) provided a detailed staging account for the chick embryo after laying. For stages between fertilization and gastrulation, Eyal-Giladi and Kochav (1975) provided a further staging regime. In the following chart Hamilton & Hamburger stages designated with Arabic numbers preceded with "HH" and Eyal-Giladi and Kochav stages are distinguished by Roman letters.


See also amazing pictures of The Birth of a Chicken

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Chicken anatomy

Animal Structures
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Chicken reproductive system
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Egg anatomy

Chicken egg anatomy

Egg shell

Egg shell structure
Cross section of the eggshell and distribution of known matrix proteins. (Jonchère V et al. BMC Genomics. 2010; 11: 57. )
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Normal chicken behaviors

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More about chicken at GeoChemBio


Apparel and various household items with this design are available at GeoChemBio shop


Prints, posters, mugs and other drinkware as well as various bags and other household items with portraits of beautiful roosters are available at GeoChemBio shop

Mix and match to create your drinkware sets, to decorate your room or to make an original gift!

Rooster 1 Rooster 2 Rooster 3
Rooster 4 Rooster 5 Rooster 6
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