The chicken or the egg – roots of the modern broiler explored

Genomics has been used to study breed formation and the roots of modern broilers.

The new study examined the historical and genetic origins of the White Plymouth Rock chicken, an important contributor to the modern broiler.

During the mid-19^th century, several chicken breeds that had been introduced to America from Europe and Asia became the founders for those formed in the USA.

Historical records about the genealogy of these populations are often unclear and inconsistent and so the research team used genomics in an attempt to describe the ancestry of the White Plymouth Rock (WPR).

In total, about 150 chickens from the WPR and 8 other stocks that historical records suggested contributed to its formation were whole-genome re-sequenced.

The admixture analyses of the autosomal and sex chromosomes showed that the WPR was likely founded as a cross between a paternal lineage that was primarily Dominique, a very old American breed, and maternal lineage where Black Java and Cochin contributed in essentially equal proportions.

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The results were consistent and provided quantification with the historical records that they were the main contributors to the WPR.

The genomic analyses also revealed genome-wide contributions from other species (<10% each) by Brahma, Langshan and Black Minorca.

Contributions to individual chromosomes were more apparent, and subsequent analyses may provide more insights into the relationship between ancestry in specific chromosome regions and long-term selection for body weight differences. This may have implications for genetic contributions to today’s broilers.

Orjan Carlborg, Professor at the Department of Medical Biochemistry and Microbiology at Uppsala University, Sweden and lead author of the study, said the livestock and poultry breeds of today were the result of foundation, isolation and selection, both natural and intentional.

“Genomic analysis has proven to be a good tool for understanding genetic contributions to breed development. Through additional study of founder contribution to chromosomes and genes, such analysis may also reveal more about the importance of conserving pure breeds and selected lines of chickens.”

• A genomic inference of the White Plymouth Rock genealogy is published in Poultry Science