Until this time, no accurate method of determining the sex of day-old chickens had been discovered. Some claimed that a ring suspended by a piece of cotton and held over a fertile egg would swing one direction for a male and the other for a female. Others claimed that egg shape indicated whether a cockerel or pullet would hatch.
In 1933, Professor Masui and Professor Hashimoto published an English version of ´Sexing baby chickens´. In 1934, Dr Kiyoshi Oxawa visited Queensland and conducted the first classes on chicken sexing and by 1935 several Queenslanders (among them Dorothy McCulloch) had become proficient.
Advantages of sexing chickens.
Enormous benefits have resulted from the ability to sex day-old chickens, not only for hatcheries but for the industry in general. The procedure has reduced the cost of rearing chickens by 50% which in turn has reduced labour and feed expenses. The advent of feather sexing has allowed the meat chicken industry (broilers) to separate males from females for a quicker turn around.
With the sexing of any normal population, you would expect to get about 50% of each sex.
There are four accepted methods for sexing day-old chickens:
- colour sexing (1975)
- feather sexing (1969)
- cloacal or vent sexing (1935)
- machine method (1950s).
Colour sexing /sex linked colour.
Commercial layer breeds have been developed in which the sex of the day-old chicken is identified by plumage (colour and markings); generally day-old males are predominantly white and females brown. The coloured layer hens produce a brown egg that is popular with consumers. Examples of sex-linked breeding are Rhode Island red or New Hampshire males over Rhode Island white or light Sussex females, with the resulting chickens being brown/red females and the white/cream with some stripes of red/brown being males.
Colour sexing as a method of sexing has had a significant impact on reducing overall costs as it is quick and easy.
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.
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 (see diagram).
Vent or cloacal sexing.
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 male eminence or lack of it (sexed as female). After a little practice this can be accomplished without injury or significant discomfort 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 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 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 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.
Instrument or machine sexing.
Instrument or machine sexing of chickens has almost disappeared, because the instruments are no longer available and spare parts cannot obtained. The Keeler Optical (English) or Chicktester (Japanese) machine features a blunt ended telescopic tube containing a light. The inserts the tube into the evacuated cloaca and with the help of the light can identify either testis or ovaries. Successful development technique depends on the capability of the student and their level of experience.
The steps for instrument sexing are as follows:
- Hold the instrument in one hand and the chicken as for vent or cloacal sexing. Thumb and first two fingers should be on either side the chicken at thigh level. Use thumb and first two fingers to provide slight pressure near the vent to evacuate faecal contents.
- Gently insert the glass tip of the machine into the chicken´s vent and down the large intestine. Extreme care is needed not to puncture the large intestine.
- Use one eye to look through the instrument while keeping the other eye open.
- The testicles are observed to the right of the backbone and look like a grain of rice usually a white/yellow colour, some breeds exhibit bit of black.
- If there are no testicles on the right, move the instrument to the left of the backbone and locate the ovary. This ovary is yellowish shaped like an inverted triangle. The right ovary is diminished and unclear.
As a few large companies control the chicken breeding and hatching industry around the world, greater numbers of geneticists and technicians are being employed in research and development. This has accelerated the already rapid trend to breed sex-linked crosses.
Consequently the skill of the chicken sexer has been superseded in the commercial industry, virtually making chicken sexing obsolete.
1. Victorian Government´s ´Agnote´ on chicken sexing (now Department of Primary Industries, Victoria), out of print.
2. ´Australasian poultry´ – school projects – Bill Stanhope.
3. Specialist chick sexer – RD Martin.