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Chick sexing is the method of distinguishing the gender of chicken and other hatchlings, usually by a trained person called a chick sexer or chicken sexer. Chicken sexing is practiced mostly by large commercial hatcheries, who have two different feeding programmes, one for the females (or hens) who are destined to lay eggs for commercial sale, and the others for the males (or cocks), most of which will be culled within days of hatching because they are irrelevant to egg production. A limited number may be kept and fattened for their meat. The chicken sexer puts the chicken hatchlings on the appropriate track early, enabling those chickens to receive optimal nourishment for their likely commercial role from an early age.
Different segments of the poultry industry sex chickens for various reasons. In farms that produce eggs, males are unwanted; for meat production, separate male and female lines for breeding are maintained to produce the hybrid birds that are sold for the table, and chicks of the wrong sex in either line are unwanted. Chicks of an unwanted sex are killed almost immediately to reduce costs to the breeder.
Methods of chick sexing 
Vent sexing 
Vent sexing, also known simply as venting, involves squeezing the feces out of the chick, which opens up the chick's anal vent (called a cloaca) slightly, allowing the chicken sexer to see if the chick has a small "bump", which would indicate that the chick is a male. Some females also have bumps, though they are rarely as large as those of male chicks.
The art of vent or cloacal sexing of day-old chickens is difficult to master without instructions from an experienced sexer. Use the following to help develop the procedure:
- Before examining the vent, discharge the chicken´s excretions by lightly pressing on both sides of the abdomen in a downward motion.
- Place the chicken on its back in the palm of your hand with the head towards you, put your thumb and first two fingers around its thighs to hold it.
- Tip your hand so that the chicken´s breast is towards you, vent uppermost.
- Place your middle fingers over the chicken´s breast to support the chicken leaving your thumb free. (If you have large hands, place the chicken´s head between your little finger and ring finger for additional support.)
- Place the thumb of your other hand on the lower portion of the vent (anus).
- Using the index finger start from the top of the vent moving down, back and around, rolling the vent in a sideways action.
- At the same time a similar action with the free thumb, starting from the top and rolling down and back.
- With the thumb and forefinger placed either side of the vent apply gentle pressure and a rolling action to evert the vent and expose the male eminence or lack of it (sexed as female). After a little practice this can be accomplished without injury or significant discomfort to the chicken.
The eminence or genital organ is found midway on the lower rim of the vent, and looks like a very small pimple. Even though its size and shape can vary considerably, it can be recognised with a little practice and a keen eye. Most males have a relatively prominent eminence, most females have none. However, a small proportion of both males and female have relatively small eminences. Sexing these chickens can be quite difficult, but with regular practice the sexer will eventually learn to identify the differences.
When learning to sex chickens it is best to assume that chickens with small eminences are female. The male eminence is solid and will not disappear upon gentle rubbing with your thumb. Having access to chickens of known sex is a great help in developing the art of vent sexing and feather-sexed meat chickens are ideal for this purpose. Professional vent sexers have studied their external appearance, which can fall into as many as fifteen basic patterns, and learned to identify which ones are male and which female.
Many professional vent sexers are Japanese, where the method originated. A seminal paper about vent sexing was published in Japan in 1933 by Professors Masui and Hashimoto, which was soon translated into English under the title sexing baby chicks. After their discovery, interested poultry breeders hired those who had been trained in Masui and Hashimoto's technique, or sent representatives to Japan to learn it.
Feather sexing 
(See also Delayed feathering in chickens)
In 1969, after three years of intensive genetic research, Tegels Poultry Breeding Company developed broiler chickens that could be feather sexed. The result was a strain that would produce slow-feathering males and fast-feathering females.
In the slow-feathering males the coverts are either the same length or longer than the primary wing feathers. In the fast-feathering females, the primary wing feathers are longer than the coverts. This is caused by a gene located on the sex chromosome where slow feathering is dominant to rapid feathering and controls the rate of wing and tail feathering in the chicken. The dominant slow-feathering characteristic is passed from mothers to their sons and the rapid feathering characteristic from the fathers to their daughters. Fathers also pass the rapid-feathering gene to their sons but this is not expressed because it is recessive. Advantages of feather sexing include:
- Increased rate of sexing (feather sexing is faster than machine sexing)
- 99% to 100% accuracy, which means lower labour costs (feather-sexing training requires less time than machine sexing)
- Easily transferable skills.
Wing-feather sexing of day-old chicks
Sexing day-old chicks by differences in the formation of wing feathers.
Alternative methods 
Small poultry farmers whose operations are not of sufficient size to warrant hiring a chicken sexer must wait until the hatchlings are four to six weeks old before learning the sexes of their chickens. At that time their secondary sex characteristics begin to appear, making it possible for anyone with a minimal amount of training to sex a chicken.
- Chick sexing was featured in episode 7 of Dirty Jobs.
- Chick sexing is Steve Smith's summer occupation on the November 16, 2008 episode of American Dad S04E06.
- Chick sexing was an important mode of employment for second-generation Japanese Americans (Nisei), who dominated the trade between the late 1930s and 1950s.
- The 'example of the chicken sexers' is famous in several debates in philosophy, especially in the internalism/externalism debate in epistemology.
- In Mr. Accident (2000) comedy Sunday Valentine (Helen Dallimore) works in an egg factory doing chick sexing.
- In the Indecision episode of QI, they briefly mentioned chicken sexing.
- In a 2013 White Collar episode S04E15 "The Original", chicken sexing is mentioned by the main character Neal.
See also 
- Poultry: Sexing of day-old chicks as a sport
- How to tell the sex of Chicks - including general signs, breed specific tips and old wives tales.
- Abstract: The art of chicken sexing - a cognitive science discussion
- The art of chicken sexing - full article (PDF)