7.4.5.1 Sexing one-day-old white layer chickens (2024)

In the commercial white egg layers, all the one-day-old commercial female chicks show fast feathering and all one-day-old commercial male chicks show slow feathering. You might guess now, what does it mean, fast or slow feathering? In fast feathered one-day-old chicks, the primary wing feathers are thicker and longer than the covert feathers, in slow feathered one-day-old chicks, the primary and the covert feathers are similar in length and thickness.

The fast or slow feathering genotype is determined by the K gene (the feather development gene). There are 4 known alleles at the K locus, in the following order of dominance: Kn > Ks > K > k+. The K gene is located on the Z chromosome (female chickens are ZW, male chickens are ZZ) and can be utilized to produce the fast and slow feathered phenotypes that distinguish between the male and female one-day-old chicks. Through controlled mating and selection, the K gene has been put into the white egg layers (the leghorns).

When in a cross fast-feathered k+k+ roosters are mated to slow-feathered K hens, the sex of their progeny can be easily recognized at the day of hatch: resulting in fast feathered female chicks k+ and slow feathered male chicks Kk+. This difference in feathering happens because female birds carry a single Z chromosome (sex chromosome), while the male birds carry two Z chromosomes.

Successful and accurate feather sexing in commercial one day-old chicks is very important. Be aware that one single sexing error made by the observer in the parent stock can generate plenty of offspring in which feather sexing can no longer be successfully applied. Especially parent stock males can have a big impact as they mate with so many females. In the white parent stock flocks, the sexing errors can easily be identified by the status of their comb: all leghorns males with non-dubbed combs should be taken out, this also accounts for the parent stock females with dubbed combs.

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