A selection of chickens

19 Apr 2012

The domesticated chicken has been around for so long that we often forget that there are still 'wild' chickens out there. Domestication was initiated at different moments and in different regions, according to archaeological and molecular genetic studies. Selective breeding was already practised during Roman times, but in the 20th century commercial breeding really kicked off, when breeders started selecting specifically for meat production or egg-laying capacity. Domestication and selection must have impacted the variation in the chicken genome when comparing domesticated breeds to their ancestors. Selecting for desired traits has however also resulted in negative effects. Current commercial lines are for example more susceptible to infections, exhibit skeletal deformities and suffer from osteoporosis.

Pooling populations
To understand how these undesirable traits emerged, it is crucial to understand which genes and regions in the genome have been affected by selection. Martin Elferink (Wagening University) and colleagues performed a broad assessment of selection histories using 67 commercial and non-commercial chicken breeds. Of each breed, multiple populations were included to decrease the influence of, for example, genetic drift in just a single population. Based on shared history and breeding goals, 14 breed groups could be formed. Elferink et al identified 396 chromosomal regions that show signs of selection, with strong evidence found for 26 regions. Including many different populations helps to reduce stochastic effects caused by a single population, the authors state.

Elferink MG, Megens HJ, Vereijken A, Hu X, Crooijmans RPMA and Groenen MAM
Signatures of selection in the genomes of commercial and non-commercial chicken breeds
PLoS ONE 7(2): e32720. doi: 10.1371/journal.pone.0032720

By: Esther Thole

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