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The pig, Sus scrofa, is a foreign species to the American continent. Although pigs originally introduced in the Americas should be related to those from the Iberian Peninsula and Canary islands, the phylogeny of current creole pigs that now populate the continent is likely to be very complex. Because of the extreme climates that America harbors, these populations also provide a unique example of a fast evolutionary phenomenon of adaptation. Here, we provide a genome wide study of these issues by genotyping, with a 60k SNP chip, 206 village pigs sampled across 14 countries and 183 pigs from outgroup breeds that are potential founders of the American populations, including wild boar, Iberian, international and Chinese breeds. Results show that American village pigs are primarily of European ancestry, although the observed genetic landscape is that of a complex conglomerate. There was no correlation between genetic and geographical distances, neither continent wide nor when analyzing specific areas. Most populations showed a clear admixed structure where the Iberian pig was not necessarily the main component, illustrating how international breeds, but also Chinese pigs, have contributed to extant genetic composition of American village pigs. We also observe that many genes related to the cardiovascular system show an increased differentiation between altiplano and genetically related pigs living near sea level., WBP is funded by COLCIENCIAS (Francisco José de Caldas fellowship 497/2009, Colombia), CAS thanks grants from CAPES and EMBRAPA (Brazil), YRC is recipient of a PhD studentship from MICINN (Spain, ref. AP2008-01450), AEC is recipient of a PhD studentship from MICINN (Spain). Work funded by Consolider CSD2007-00036 ‘Center for Research in Agrigenomics’ and AGL2010-14822 grants (Spain) to MPE, EU SABRE project FOOD-CT-2006-01625, USDA project 2007-04315 (USA), Facultad de Ciencias Agrarias, San Pedro (UNA), Unión de Gremios de la Producción (UGP) and Empresa San Rafael Agricola y Ganadera SRL (Paraguay), Universidad Técnica de Oruro (Bolivia), Programa de Conservación de los Bancos de Germoplasma, Instituto Colombiano Agropecuario (grant 048-2011) and Ministerio de Agricultura y Desarrollo Rural (Colombia), and Centro de Validación de Tecnologías Agropecuarias (CEDEVA, Formosa, Argentina).

International audience; An evaluation of the European pig diversity has been carried on by several countries, with the support of the European Union over the period of 1994 to 2000. This article presents an overview of the results of this investigation, focussing on two genetic marker techniques, namely microsatellites (MS) and amplification of fragment length polymorphism (AFLP). Nearly 200 loci were characterised on about 50 individuals from each of 59 to 71 breeds, according to the marker considered. The analysis of diversity, based on genetic distances, led to similar conclusions for the two marker types (MS and AFLP), in spite of a markedly lower total diversity of AFLP compared to MS. The analysis of the MS loci showed that the allelic diversity pattern among breeds was quasi-independent from the diversity pattern based on allele frequencies. Genetic distances showed no particular clustering of local with international breeds, confirming the genetic uniqueness of the European local breeds compared to mainstream international breeds. The taxonomy of the local breeds revealed a cluster of the Iberian type breeds, in contrast with a wider dispersal of the breeds from other countries. Phylogeny often disagreed with documented breeds’ history, showing the complex migration/admixture patterns which underlie the breeds’ relationships. Methodologies developed in this investigation as well as the database and the DNA depository created should provide support for further innovative research in the field of domestic animal diversity management.

Microsatellite diversity in European and Chinese pigs was assessed using a pooled sampling method on 52 European and 46 Chinese pig populations. A Neighbor Joining analysis on genetic distances revealed that European breeds were grouped together and showed little evidence for geographic structure, although a southern European and English group could tentatively be assigned. Populations from international breeds formed breed specific clusters. The Chinese breeds formed a second major group, with the Sino-European synthetic Tia Meslan in-between the two large clusters. Within Chinese breeds, in contrast to the European pigs, a large degree of geographic structure was noted, in line with previous classification schemes for Chinese pigs that were based on morphology and geography. The Northern Chinese breeds were most similar to the European breeds. Although some overlap exists, Chinese breeds showed a higher average degree of heterozygosity and genetic distance compared to European ones. Between breed diversity was even more pronounced and was the highest in the Central Chinese pigs, reflecting the geographically central position in China. Comparing correlations between genetic distance and heterozygosity revealed that China and Europe represent different domestication or breed formation processes. A likely cause is a more diverse wild boar population in Asia, but various other possible contributing factors are discussed.

Genetic diversity within and between breeds (and lines) of pigs was investigated. The sample comprised 68 European domestic breeds (and lines), including 29 local breeds, 18 varieties of major international breeds, namely Duroc, Hampshire, Landrace, Large White and Pietrain, and 21 commercial lines either purebred or synthetic, to which the Chinese Meishan and a sample of European wild pig were added. On average 46 animals per breed were sampled (range 12–68). The genetic markers were microsatellites (50 loci) and AFLP (amplified fragment length polymorphism, 148 loci). The analysis of diversity showed that the local breeds accounted for 56% of the total European between-breed microsatellite diversity, and slightly less for AFLP, followed by commercial lines and international breeds. Conversely, the group of international breeds contributed most to within-breed diversity, followed by commercial lines and local breeds. Individual breed contributions to the overall European between- and within-breed diversity were estimated. The range in between-breed diversity contributions among the 68 breeds was 0.04–3.94% for microsatellites and 0.24–2.94% for AFLP. The within-breed diversity contributions varied very little for both types of markers, but microsatellite contributions were negatively correlated with the between-breed contributions, so care is needed in balancing the two types of contribution when making conservation decisions. By taking into account the risks of extinction of the 29 local breeds, a cryopreservation potential (priority) was estimated for each of them.

Kinetics of postmortem muscle changes of two pig breeds were studied. pH was measured at 30 min (pH1) and 26 h (pH2) after slaughter. The longissimus thoracis et lumborum was used at 1, 2, 3, 6 and 14 days postmortem for measurements of sarcomere length and mechanical properties in the raw state, and cooking loss and mechanical properties after cooking. Electron microscopy was performed at 1, 6 and 14 days postmortem. pH1 was higher and the maximum stress lower in Large Whites than in Pietrains. Maximum stress of cooked meat decreased with aging time in Large Whites but not in Pietrains. Ultrastructural changes were more obvious in Large Whites than in Pietrains through day 6, but breed differences were no longer observed at day 14. Meat from Pietrain pigs was tougher than that from Large White pigs and tenderized at a slower rate and to a lesser extent during aging.