The ability to sex day-old baby chickens is important because each gender has its own importance in the poultry industry. Hens, or female chickens, are raised to become egg producers while roosters, or male chickens, are raised to become meat producers. Knowing the sex of the day-old chickens saves the producers of these poultry products from raising them until they are old enough to tell apart simply by looking. It takes four to six weeks for secondary sex characteristics such as the size and shape of the comb, to become visible enough to distinguish between the two sexes. However, sexing is not easy due to the location of the sex organs inside the body of the chicken.
Sexing was not proven accurate until the 1930s, when two Japanese professors perfected their technique. This technique became the first of four methods commonly accepted, known as cloacal or vent sexing. The remaining methods are the machine method, feather sexing and color sexing.
- Cloacal, or vent sexing, was the first method perfected and is the oldest method used today to distinguish between day-old hens and roosters. Although this method is not easy to accomplish, with proper training and experience, the individual performing it can generally get positive results. This method involves examining the baby chicken's vent, located under its tail, looking for a genital organ. If the genital organ is present in the vent, it will resemble a small pimple and the chicken is a rooster.
- Machine sexing is the second oldest method of sexing. The machine method came into existence in the 1950s. Today these machines, the Keeler Optical and the Chicktester, are no longer in production and there are no parts in production for the machines that may still be used. These machines worked by a telescopic tube with a light inserted into an evacuated vent of the baby chicken in question. The tester carefully looks into the lens of the instrument and makes a determination of the sex of the chicken by seeing whether the chicken has testes or ovaries.
- Feather sexing became possible in 1969 after several years of genetic research by the Tegels Poultry Breeding Company. This method is only possible if a female from a slow-feathering breed is crossed with a male from a fast-feathering breed. The sex of the chicks produced from this cross can be determined during the first 48 hours after hatching by looking at the primary and secondary feathers located on the chick's wings. The primary feathers will be noticeably longer than the secondary feathers on a female chick. On a male, the primary and secondary feathers are the same length.
- Color sexing is the newest method of determining the sex of a day-old chicken. In 1975, commercial breeders were developed and the chicks of these breeders can be identified as hens and roosters by the color of their plumage. The plumage on hens is generally white while the plumage on roosters is brown.