**2. Brazilian naturalized sheep**

**1. Introduction**

38 Livestock Science

sheep [2].

considered naturalized, locally adapted or native [1].

animals, wildlife, and endangered species [3, 4].

abundance in gene flow [6].

analyzed [8].

Brazil has several breeds of sheep, including animals that developed from breeds brought by settlers soon after the discovery. Over the years, these animals were under the process of natural selection of local environmental and climatic conditions, resulting in breeds that are

Thus, the characterization of the diversity of naturalized breeds, the genetic relationship between them, as well as knowledge of their origins in other breeds are the first step to obtain subsidies for breeding programs, management, and conservation of naturalized Brazilian

Molecular tools and recent technologies have marked the discovery of the source and domes‐ tication processes of species, both using molecular markers such as mitochondrial DNA (mtDNA). These tools have aided the understanding of evolutionary relationships, taxono‐ mies, demographics of various species and provided support to identify the most important areas for conservation programs, and assist in the analysis of genetic diversity in domestic

The mtDNA shows the haplotype diversity within species; therefore, it becomes a useful tool to establish phylogenetic relationships between the species [5]. On the other hand, the haploid inheritance of markers of the Y chromosome makes them to be extremely sensitive for detecting genetic history, the process of domestication, the relationship between population and the male

The Pantaneiro sheep showed greater allelic richness when compared with other populations in a study with other six breeds in the state of Mato Grosso do Sul, Brazil [7]. Considering that the introduction of sheep in South America has occurred concomitant with the process of colonization and the effective population size is in process of formation, high levels of diversity observed in the different studied populations can be related to the fact of selective pressure coupled with miscegenation have implicated in the introgression of genes in populations. Analyzing the haplotypes found in mtDNA, it was observed that the Pantaneiro sheep was distributed in seven haplotypes and grouped with all other locally adapted breeds that were

A study performed with Creole breed demonstrated that these animals have a different haplotype compared to the animals of Pantaneiro breed, as there was no grouping in the same network [9]. This suggests a difference between these groups, so more research would be needed to see if it is enough that the Pantaneiro sheep can be recognized as a distinct breed [10]. However, it was also observed that several haplotypes for the Creole breed were close to haplotype formed by Pantaneiro breed which could indicate that, although these animals do not share the same haplotype, they belong to the same haplogroup. The regions where these animals currently found previously belonged to Paraguay, so it is possible that Pantaneiro breed has been influenced by Paraguayan herds. Analysis of their mitochondrial genome can redeem this history showing their genetic diversity from the Creole breed. Thus, the existence of significant differences in the ND5 gene of mtDNA between Pantaneiro and Creole breeds Domestic sheep are belonging to the Bovidae family, *Ovis* genus and *Ovis aries* species. The sheep were the first animals to be domesticated, and it is believed that its origin is descended from the Muflon (*Ovis musimon*) and Urial (*Ovis orientalis*) breeds, since the Urial breed may have contributed to the formation of all European sheep breeds [13].

Brazilian sheep breeds, as well as several species of domestic animals in the country were introduced by Portuguese colonization. Over the years, they have been subjected to natural selection because of their adaptation and survival to the local environmental and climatic conditions, resulting in breeds that are now considered locally adapted or local, creole and native or naturalized [1, 2].

Brazilian naturalized sheep are small and specialized in intensive meat or milk production system, so far they have not undergone to selection process and genetic breeding [2]. These breeds were known for their rusticity and ability of adaptation to tropical and subtropical climate regions, allowing them to hold important attributes of genetic resources. These animals still have tolerance or resistance to disease and parasites, as well as adaptation to availability of food resources and water [14].

However, the search for more productive breeds from the ending of the nineteenth century and the beginning of the twentieth century led to import exotic breeds from temperate climatic region, which did not have the adaptive traits of local breeds. This way, it occurred indiscrimi‐ nate crossings, which was determinant to result in rapid replacement and erosion of natural‐ ized animals, endangering their existence [15].

In order to prevent the extinction of naturalized breeds and their genetic heritage, in 1983, the National Research Center for Genetic Resources and Biotechnology (Cenargen) of the Brazilian Agricultural Research Corporation (Embrapa) decided to include animal genetic resource conservation research in its Genetic Resources Conservation program (Brazilian Animal Genetic Resources Conservation program) [16]. Since then, in addition to Cenargen, several Embrapa centers, universities, private companies, and farmers have maintained the conser‐ vation of animals, through natural selection and semen, embryos, and oocytes storage in germplasm banks [17].
