Red Junglefowl, the closest living relative to the domestic chicken, are not known for their egg laying abilities. However, over the last 8,000 years humans have selectively bred the ancestors of modern chickens for traits such as; fighting ability, body size and egg laying abilities, creating a plethora of different chicken breeds. Divergence between meat (broiler) and egg (layer) chickens began between the late 19^th to early 20^th century evolving into the current poultry practices of the 21^st century. Almost all commercial laying chicken breeding is conducted by a handful of companies within Europe; Hendrix (Netherlands), Erich Wesjohann (Germany) and Group Grimaud (France). These three companies are responsible for the care and breeding of the European grandparent- and parental-flocks. These breeding populations are extremely valuable and contain a mixed sex population; where females and males are often different breeds in order to produce hybridised offspring. Except in the case of commercial leghorn chickens, where the parental flock are selected lines of leghorns. Fertile eggs from these grandparent- and parental-flocks are then shipped throughout Europe to hatcheries ready to incubate their own parental flocks or next generation of commercial laying hens (Nicol, 2015).

Photo source: https://www.cacklehatchery.com/red-junglefowl.html, https://zootecnicainternational.com/poultry-facts/latest-innovations-future-advances-genetics-lohmann-tierzucht/, https://www.exportersindia.com/pune/broiler-chickens.html, https://www.vectorstock.com/royalty-free-vector/poultry-farming-chicken-breeds-icon-set-flat-vector-17021260

1. When eggs arrive at a hatchery they go through an egg washing machine before being placed in large cabinet incubators. These fan heated cabinet incubators often contain several thousand eggs at one time and are controlled automatically for temperature and humidity. The eggs remain in the incubators until day 19 of incubation.
2. At this stage of the eggs are then removed from the incubators, transported by machinery into hatching trays.
3. The eggs are then placed in hatching machines.
4. Trays of newly hatched chickens are removed from the hatchers and the egg shells are seperated by hand.
5. Commercial brown chickens are sex-linked therefore can be sexed immediately through feather colouration. Female commercial browns are brown/orange and males are white/yellow. The males are discarded immediately after leaving the hatchers.
6. The commercial white chickens have no colour differences upon hatching so both males and female are transported via conveyer belts to the sorting room.
7. The white commercial chickens are manually sex sorted by looking at the developing wing feathers or in some cases cloacae sexed. The males are discarded from the process and transported to a different room where they are culled in a gas machine.
8. The female chickens are then transported on the conveyer belt system to a vaccination station where they are vaccinated by automatic dispensing machines.
9. Once vaccinated the chickens are transported on another conveyor belt system, this time with multiple drops and differing speeds in order to prevent the chickens clustering so they can be counted by a machine and dropped into transportation crates containing 104 chickens.

The chickens then remain in these transportation crates until the whole batch of up to 10,000 chickens have been through the sorting process. The newly hatched chickens are then loaded onto specially designed transport vehicles which maintain temperature and humidity levels for the chickens for a journey of up to a maximum of eleven hours.

Photo sources: https://www.mypetchicken.com/images/product_images/Popup/chicks_white_leghorn1.jpg, http://www.thepoultrysite.com/articles/contents/08-04-05Eggs.jpg, https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTDDxYKEVxGlcQutkdzl8aQYPk-f6n0YMUnfb4Usd1lVRztzMR0Bw, https://i1.wp.com/www.myanimalmyhealth.org/wp-content/uploads/2018/02/vaccination-in-poultry.jpg?fit=696%2C464&ssl=1, https://devhensbrood.files.wordpress.com/2014/05/red_sex_link_chicks.jpg, https://ae01.alicdn.com/kf/HTB1k904LpXXXXc4aXXXq6xXFXXX2/1-Set-Of-Incubation-Equipment-Accessories-50-35-6-2-5cm-White-Plastic-88-Egg-Tray.jpg_220x220.jpg, http://www.irvineschicken.co.zw/wp-content/uploads/2016/03/Irvines-Commercial-Hatchery-Equipment.jpg, http://www.brightfarmhouse.com/wp-content/uploads/2016/02/background5.jpg, http://www.nnybizmag.com/wp-content/uploads/2012/05/0501_biz_Hatchery2-300x209.jpg, http://bergshatchery.com/images/sexing-pullet.jpg