Pigs which are bred commercially in Europe are found to have a highly varied mosaic of different European and Asian gene variants. The Asian genes in particular result in a large number of piglets in European pig breeds. In the latest issue of the science journal Nature Communications, researchers from Wageningen University explain that a number of important characteristics of European pigs have Asian origins. They previously demonstrated that the genetic diversity among commercial pigs is greater than within the existing populations of wild boar.
The pig we know today has a long history since the original independent domestication of the wild boar in Europe and Asia some 10,000 years ago. This domestication resulted in European and Asian pig breeds with very different characteristics and appearance. Modern commercial European pigs contain DNA originating from Asia. According to the researchers, the genetic diversity in commercial pigs is greater than in existing wild boar populations as a result.
The Wageningen research has demonstrated that different parts of the genome of commercial pigs are much closer to Chinese pigs than to European wild boar. 'At first sight that seems surprising because pigs in Asia and Europe were domesticated independently from one another around ten thousand years ago and you would therefore expect there to be no traces of Asian DNA in European pigs', says Professor Martien Groenen, under whose leadership the research took place.
In Nature Communications, he and his colleagues explain that the finding has its origin in the UK in the late 18th and early 19th centuries. This is because there was a strong rise in the demand for pork during the Industrial Revolution and pig farmers in the UK in particular saw that Asian pigs had characteristics they wanted to improve in their own pigs. In general, Chinese pigs were much more fertile and fatter than their European counterparts. So breeders imported a number of Chinese individuals around this time and crossed them with their own European pigs. The greater genetic diversity within the current commercial pig breeds is therefore the result of crosses between European and Chinese pigs around two hundred years ago.
Strong selection for characteristics such as fertility and fat production of the Asian pigs subsequently ensured that some pieces of Asian DNA are present at high frequency in the European pigs. An example is the AHR gene, of which many European pigs have the Asian version. Sows with the European gene have significantly fewer piglets than carriers of the Asian version.
- Mirte Bosse, Hendrik-Jan Megens, Laurent A. F. Frantz, Ole Madsen, Greger Larson, Yogesh Paudel, Naomi Duijvesteijn, Barbara Harlizius, Yanick Hagemeijer, Richard P. M. A. Crooijmans, Martien A. M. Groenen. Genomic analysis reveals selection for Asian genes in European pigs following human-mediated introgression. Nature Communications, 2014; 5 DOI: 10.1038/ncomms5392
- Mirte Bosse, Hendrik-Jan Megens, Ole Madsen, Laurent A.F. Frantz, Yogesh Paudel, Richard P.M.A. Crooijmans, Martien A.M. Groenen. Untangling the hybrid nature of modern pig genomes: a mosaic derived from biogeographically distinct and highly divergentSus scrofapopulations. Molecular Ecology, 2014; DOI: 10.1111/mec.12807
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