Smriti Sharma, Priyanka, Ravinder and Gitesh Saini
Department of Animal Genetics and Breeding, Lala Lajpat Rai University of Veterinary and Animal Sciences (LUVAS), Hisar-125004, Haryana, India
Department of Public Health and Epidemiology, Lala Lajpat Rai University of Veterinary and Animal Sciences (LUVAS), Hisar-125004, Haryana, India
Department of Animal Nutrition, Lala Lajpat Rai University of Veterinary and Animal Sciences (LUVAS), Hisar-125004, Haryana, India
Department of Veterinary Gynaecology and Obstetrics, Lala Lajpat Rai University of Veterinary and Animal Sciences (LUVAS), Hisar-125004, Haryana, India
Introduction: Chick sexing is the method of distinguishing the sex of chickens and other hatchlings, usually by a trained person called a chick sexer or chicken sexer. Mostly large commercial hatcheries practice chicken sexing to separate female chicks or “pullets” (to lay eggs) from the males or “cockerels” (most of them are killed within days of hatching due to their irrelevance to egg production). For commercial roles, large number of females and a limited number of males are kept on different feeding programs. Various section of poultry industry requires chick sexing 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
Several methods are used to determine the sex of a day-old chick. Some are effective only with certain breeds or crosses, while others are universal. The two chief methods of sexing chicks are feather sexing and vent sexing.
Vent sexing: Venting, also known simply as vent sexing, 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 but not as large as those of male chicks.
The eminence or genital organ is observed halfway at the lower rim of the vent and looks like a very small pimple. Maximum males have an extraordinarily prominent eminence, maximum ladies have none. However, a small percentage of both males and female have highly small eminences. When learning to intercourse chickens, it’s miles first-rate to expect that chickens with small eminences are female. The male eminence is strong and will no longer disappear upon gentle rubbing with one’s thumb.
Vent sexing was developed in Japan and in 1930s, it was taken to North American poultry producers. Vent sexing is an ability that takes a long time to increase. It includes maintaining the chick the other way up in a single hand, expelling the faecal material, and everting (turning outward) the vent area. The character can then search for the presence or absence of a rudimentary male sex organ. This technique sounds a good deal simpler than it really is. To appropriately sex chicks in this manner, individual want to be properly educated and to have had an outstanding deal of practice.
Feather sexing: The sex-linked slow-feathering gene can be used in the crosses where the sex of the chicks can be ascertained at hatching time by the length of the wing feathers. A cross between a fast-feathering male and a slow-feathering female results in chicks in which females have primary wing feathers that are significantly longer than the coverts. The male chicks have shorter primary wing feathers, almost the same length as the coverts.
Feather sexing day old chicks in the Hatchery
- It is important to sort day-old chicks by sex at the hatchery.
- To identify females for further selection.
- To distinct male and female broilers to manage them according to their differing requirements.
For example, Rhode Island Red and New Hampshire breeds can be sexed by observing wing color at hatching. White spot on the down over the wing web can be seen in male chicks. This spot is lost when the chick down is shed and replaced with feathers. But sexing in this way is not always accurate as there is considerable normal variation in the size of the spot.
The Barred Plymouth Rock breed carries a gene for barring (B) that is carried on the Z chromosome. This gene produces a white bar on an otherwise black feather. The gene is incompletely dominant over the non-barring gene (b). In adults, the male, with two barring genes (BB), has feathers with broader white bars than those of the female, who has only one of the barring genes (B_). As a result, females are overall lighter in color. The sex of purebred Barred Plymouth Rocks chicks can be determined based on the size and shape of a light-coloured spot on the top of the head. Large white spot at hatch is present in males. In females, the spot is much smaller and narrower. This has been found to be about 80% accurate.
Advantages as compared with vent sexing:
- People can be trained to feather sexing quickly with good speed and accuracy.
- Feather sexing can be done at fast rate (up to 4,500 chicks per person per hour).
- Less chances of infection and cost effective.
Colour sexing: The sex-linked silver/gold (Ss) gene can also be used to sex newly hatched chicks. S females mated with S males give birth to offspring, females have a darker, leathery downcolor, and males have a brighter, whiter downcolor. Unless concealed by other colors (controlled by other genes), chicks can be sexed accurately with little or no training.
Auto-sexing breeds: In 1930, two English geneticists elaborated the principle of sex linkage to sex identification of baby chicks without depending to breed crosses. This method is known as autosexing, it involves the interaction of a sex-linked gene-the barring gene with certain other genes in a pure-breeding variety or strain of chickens. Males carry two genes for barring which modify the color or pattern expressed in the chick down feathers by the action of other genes in a more severe fashion than one barring gene in females. This method enables the development of a purebreeding variety in which the sexes consistently appear distinct at hatching. Some of the inherited traits in chickens with which the barring gene will interact to give autosexing are parallel penciling, a striped chick down pattern, and the down pattern of mottled breeds like the Ancona.
Semi-auto-sexing breeds: Newly hatched Barred Rocks, Rhode Island Reds, and New Hampshire Reds can be sexed distinctly with fair accuracy. With Barred Rocks, the males have a large, distinct white head spot and yellow feet whereas females have a smaller, less well-defined head spot and darker feet. Rhode Island Red and New Hampshire Red chicks with chipmunk stripes are mostly females.
Alternative methods: Small scale poultry owners can’t afford a chicken sexer therefore, to avoid waiting for a long period of 4-6 weeks to attain the observable distinction in characters, there are provision of some alternative methods of sexing the chicks.
In-ovo sexing: Automated systems to determine the sex of the developing chick long before hatching have been announced but not widely deployed. A high accuracy of 97% in 14-day in-ovo experiment was reported in 2017. The system relies on candling eggs and using spectroscopy to determine feather colour, and hence is suitable only for strains with sex-linked feather colouration.
Machine sexing: Due to non-availability of instruments and spare parts of machine sexing, there is not widely used. The Keeler Optical (English) or Chick tester (Japanese) machine features a blunt-ended telescopic tube, containing a light. The chicken sexer inserts the tube into the evacuated cloaca and with the help of the light can identify either testis or ovaries.
Conclusion: With most animals, it is relatively easy to determine the sex of the newborn. The male reproductive organs are located on the outside of the body and are relatively easy to see, even in newborns. This is not the case with poultry. In male birds, the reproductive organs are inside the body cavity. This makes sexing newly hatched chicks difficult. Therefore, various methods of chick sexing were developed to sex the chicks as early as possible to assort the chicks for different purposes like egg production or meat production or to develop as breeder flock.