# Differentiating Pigs from Wild Boars Based on _Nr6a1_ and _Mc1r_ Gene Polymorphisms
## 1 Introduction  
Conscious consumers search for food products consisting of defined reliable components. Wild boar meat products appear to be healthier than farmed pork products because the animals grow in a natural environment without any artificial nutritional additives. Although a porcine component can be simply identified, the differentiation between wild boar and domestic pig in meat products is still challenging [1, 2]. The melanocortin 1 receptor (_MC1R_) gene, also called the extension locus (E), plays a key role in the pigmentation of skin and hair in mammals by regulating the synthesis of two dyes: eumelanin (brown to black) and pheomelanin (cream to red) in melanocytes [3]. Binding of _MC1R_ to the \(\alpha\)- melanocyte-stimulating hormone (\(\alpha\)MSH) stimulates eumelanin production. The opposite effect results when ASIP (Agoutin Signaling Protein) binds to \(\alpha\)MSH, which causes the synthesis of pheomelains. These genes show epistatic interaction [4, 5]. In studies conducted by [6, 7] on domestic pigs (_Sus scrofa f. domestica_) and Central European wild boars (_Sus scrofa scrofa_), several _MC1R_ alleles were identified, one of which (E+) is considered the\"wild\" allele, and has been predominantly assigned to the wild boar population. Other alleles are prevalent in domestic pig breeds: dominant black (ED1 and ED2), black spotting (EP), and red (e) [6; 7]. In [8], the authors conducted the first study aiming to differentiate between wild boars and commercial pig breeds based on combining both nuclear (melanocortin 1 receptor, \(MC1R\)) and mitochondrial DNA (D-loop). This analysis of \(MC1R\) proved to be more effective than the most common method used for species identification based on polymorphisms of mitochondrial DNA. The subspecies also differ in vertebrae; wild boars usually have 19 thoracic and dorsal vertebrae, whereas domestic pig breeds have 21-23. In [9], the authors identified a missense substitution (p.Pro192 Leu) in the nuclear receptor subfamily 6, group A, member 1 (\(NR6A1\)) gene as a causative mutation of a QTL, which affects the number of vertebrae in pigs. In genetic research, the analysis of the history of breed development is of great importance. After World War II started, Poland begun breeding work aimed to stabilise pure breeds of pigs, sheep, and horses and keep primitive native breeds from extinction [10]. The Pulawska breed is the first native breed of pigs in Poland. It was created by crossing the regional primitive breeds with Berkshire and English Large White breeds. The pigs are spotted, black and white, with a prevailing black colour [11]. The tri-colour is also accepted: black-white, red and black, with white spots in the lower part of the snout, legs and tail (accessed on 25 May 2021; [[http://www.bioroznorodnosc.izoo.krakow.pl/swinie/pulawska](http://www.bioroznorodnosc.izoo.krakow.pl/swinie/pulawska)]([http://www.bioroznorodnosc.izoo.krakow.pl/swinie/pulawska](http://www.bioroznorodnosc.izoo.krakow.pl/swinie/pulawska)); in Polish). The Polish landrace was settled using German and Swedish national breeds. The landrace pigs are white-skinned and covered with white hair. Small dark spots are also acceptable (accessed on 25 May 2021; [[https://www.polsus.pl/index.php/en/pig-breeding/breeds/polish-landrace](https://www.polsus.pl/index.php/en/pig-breeding/breeds/polish-landrace)]([https://www.polsus.pl/index.php/en/pig-breeding/breeds/polish-landrace](https://www.polsus.pl/index.php/en/pig-breeding/breeds/polish-landrace))). The Polish Large White breed was created before World War II, although unfortunately, these breeding achievements were lost. The current breed was settled in 1947 based on large white pigs imported from England and Sweden.