Variations in body weight and in the distribution of body fat are associated with feed availability, thermoregulation, and energy reserve. Ethiopia is characterized by distinct agro-ecological and human ethnic farmer diversity of ancient origin, which have impacted on the variation of its indigenous livestock. Here, we investigate autosomal genome-wide profiles of 11 Ethiopian indigenous sheep populations using the Illumina Ovine 50 K SNP BeadChip assay. Sheep from the Caribbean, Europe, Middle East, China, and western, northern and southern Africa were included to address globally, the genetic variation and history of Ethiopian populations. Population relationship and structure analysis separated Ethiopian indigenous fat-tail sheep from their North African and Middle Eastern counterparts. It indicates two main genetic backgrounds and supports two distinct genetic histories for African fat-tail sheep. Within Ethiopian sheep, our results show that the short fat-tail sheep do not represent a monophyletic group. Four genetic backgrounds are present in Ethiopian indigenous sheep but at different proportions among the fat-rump and the long fat-tail sheep from western and southern Ethiopia. The Ethiopian fat-rump sheep share a genetic background with Sudanese thin-tail sheep. Genome-wide selection signature analysis identified eight putative candidate regions spanning genes influencing growth traits and fat deposition (NPR2, HINT2, SPAG8, INSR), development of limbs and skeleton, and tail formation (ALX4, HOXB13, BMP4), embryonic development of tendons, bones and cartilages (EYA2, SULF2), regulation of body temperature (TRPM8), body weight and height variation (DIS3L2), control of lipogenesis and intracellular transport of long-chain fatty acids (FABP3), the occurrence and morphology of horns (RXFP2), and response to heat stress (DNAJC18). Our findings suggest that Ethiopian fat-tail sheep represent a uniquely admixed but distinct genepool that presents an important resource for understanding the genetic control of skeletal growth, fat metabolism and associated physiological processes.

How animals, particularly livestock, adapt to various climates and environments over short evolutionary time is of fundamental biological interest. Further, understanding the genetic mechanisms of adaptation in indigenous livestock populations is important for designing appropriate breeding programs to cope with the impacts of changing climate. Here we conducted a comprehensive genomic analysis of diversity, interspecies introgression and climate-mediated selective signatures in a global sample of sheep and their wild relatives. By examining 600k and 50k genome-wide SNP data from 3447 samples representing 111 domestic sheep populations and 403 samples from all their seven wild relatives (argali, Asiatic mouflon, European mouflon, urial, snow sheep, bighorn and thinhorn sheep), coupled with 88 whole-genome sequences, we detected clear signals of common introgression from wild relatives into sympatric domestic populations, thereby increasing their genomic diversities. The introgressions provided beneficial genetic variants in native populations, which were significantly associated with local climatic adaptation. We observed common introgression signals of alleles in olfactory-related genes (e.g., ADCY3 and TRPV1) and the PADI gene family including in particular PADI2, which is associated with antibacterial innate immunity. Further analyses of whole-genome sequences showed that the introgressed alleles in a specific region of PADI2 (chr2: 248302667-248306614) correlate with resistance to pneumonia. We conclude that wild introgression enhanced climatic adaptation and resistance to pneumonia in sheep. This has enabled them to adapt to varying climatic and environmental conditions after domestication.

Fat tail in sheep represents a valuable energy reserve for facing future climate changes. The identification of genes with a role in the fat-tail phenotype may contribute to understanding the physiology of fat deposition and the mechanisms of adaptation. Genotypic data obtained with the OvineSNP50K array in 13 thin-tail sheep breeds from Italy were used to identify selection signatures of fat tail through pairwise thin- versus fat-tail sheep breed comparisons, with the following fat-tail breeds of the Mediterranean area: two unique Italian fat-tail breeds (Barbaresca and Laticauda), a Barbary sheep breed from Libya, Ossimi breed from Egypt, Cyprus Fat-Tail and Chios from the Greek islands Cyprus and Chios, respectively. Fst and χ2 values obtained for >40000 polymorphic markers allowed confirmation of 12 fat-tail associations that were previously reported in Chinese and Iranian breeds. Two of these signals – on OAR 7 and OAR 13 – are in the proximity of two genes – VRTN and BMP2 – with a role in the variation of vertebral number and in fat-tail formation respectively. Two identified signals on OAR 6 and OAR 15 encompass two genes, PDGFRA and PDGFD, involved in the differentiation of preadipocytes. Further signals detected herein were reported in Chinese sheep as signatures of adaptation to desert areas. For several of the detected associations, the known role in either fat deposition or adaptation, thus contributing to revealing the molecular basis underlying mechanisms of energy storage and climate adaptation.

Gastrointestinal nematode (GIN) infections have negative impacts on animal health, welfare and production. Information from molecular studies can highlight the underlying genetic mechanisms that enhance host resistance to GIN. However, such information often lacks for traditionally managed indigenous livestock. Here, we analysed 600 K single nucleotide polymorphism genotypes of GIN infected and non-infected traditionally managed autochthonous Tunisian sheep grazing communal natural pastures. Population structure analysis did not find genetic differentiation that is consistent with infection status. However, by contrasting the infected versus non-infected cohorts using ROH, LR-GWAS, FST and XP-EHH, we identified 35 candidate regions that overlapped between at least two methods. Nineteen regions harboured QTLs for parasite resistance, immune capacity and disease susceptibility and, ten regions harboured QTLs for production (growth) and meat and carcass (fatness and anatomy) traits. The analysis also revealed candidate regions spanning genes enhancing innate immune defence (SLC22A4, SLC22A5, IL-4, IL-13), intestinal wound healing/repair (IL-4, VIL1, CXCR1, CXCR2) and GIN expulsion (IL-4, IL-13). Our results suggest that traditionally managed indigenous sheep have evolved multiple strategies that evoke and enhance GIN resistance and developmental stability. They confirm the importance of obtaining information from indigenous sheep to investigate genomic regions of functional significance in understanding the architecture of GIN resistance.