Environmental stressors have, over generations, influenced the morphology, anatomy, behaviour, physiology, and genetic structure of small ruminants. The widespread dispersal of small ruminants over vast geographical areas occurred along with human migration, thereby promoting the adaptative process to different environmental conditions mainly through natural selection. Ongoing global warming prompted scientific efforts to deepen the knowledge and understanding of adaptation traits in small ruminants. Compared to other ruminants, sheep and goats seem to have a better adaptation ability to environmental stressors, as evident by their presence across different geographic areas on a global level. Adaptation to a specific environment leads to variations in precise genomic regions, allowing for the identification and selection of animals with a high capacity of adaptation to environmental stressors. Rapid development in sequencing technologies, together with bioinformatics tools, make it possible to analyse the genomic regions related to environmental adaptation. Hence, the aims of this review were (i) to outline the main steps of the evolution process in sheep and goat species, (ii) to summarise candidate genes related to environmental adaptation, and (iii) to evaluate both selection and conservation possibilities of these genes in native small ruminant breeds for future challenges to better face the global warming.

Via long‐term natural and artificial selection pressure, homozygosity may extend across the genome, leaving genomic patterns called selection signatures. This study is the first attempt to assess genome‐wide selection signatures in six native Turkish and two cosmopolitan cattle breeds by 211.119 bi‐allelic SNPs recovered using the double digest restriction associated DNA sequencing method. The integrated haplotype score (iHS) statistic was utilised to reveal selection signatures within populations, whereas the cross‐population extended haplotype homozygosity (XP‐EHH) and fixation index (F_ST) approaches were preferred to reveal differently fixed genomic regions between native Turkish and cosmopolitan cattle breeds. Selection signatures in 142 genomic regions containing 305 genes were detected within eight cattle breeds by iHS statistics. The XP‐EHH and F_ST approaches revealed that 197 and 114 SNPs were under selection pressure, respectively, which overlapped with 144 and 190 genes, respectively. A total of 18 genes were detected by at least two approaches. Six genes related to disease resistance (TTP2), meat yield (DIAPH3 and METTL21C), meat quality (ZNF24 and ZNF397) and first calving interval (ZSCAN30) turned out to be differently fixed between native Turkish and cosmopolitan cattle breeds, as they were identified by both XP‐EHH and F_ST approaches. In addition, the iHS approach revealed that eight genes associated with visual modality (LSGN), olfaction (MOXD2, OR4C1F and OR4C1F), and immune response (TRBV3‐1 and CLDN10) were under selection pressure in both native and cosmopolitan cattle breeds. Owing to their being significantly related to survival traits, these regions may have played a key role in cattle genome evolution. Future studies utilising denser genetic data are required to obtain deeper knowledge on effects of natural and artificial selection in Anatolian cattle breeds. © 2023 Stichting International Foundation for Animal Genetics.

This is the first comprehensive study to reveal genetic variation and population structure at genome level in six Anatolian (Anatolian Black, East Anatolian Red, South Anatolian Red, South Anatolian Yellow, Turkish Grey Steppe, and Zavot) and two cosmopolitan (Brown Swiss and Holstein Friesian) cattle breeds reared in Türkiye. Being 20 samples from each population, a total of 160 blood samples retrieved from representative herds were utilized to generate genomic libraries by ddRADseq method. Genomic libraries sequenced by Illumina HiSeq X Ten instrument revealed a total of 211,119 bi-allelic SNPs with high call rate. Compared to cosmopolitan cattle breeds, a higher genetic variation was observed in native Turkish cattle with an average of 0.380 observed heterozygosity. Genetic distances were comparatively low between native cattle breeds, whereas the highest genetic distance (0.064) was detected between South Anatolian Yellow and Brown Swiss. Population structure analyses showed that the native Turkish and cosmopolitan cattle breeds were clearly different from each other according to their phylogenetic origin. Besides, a high level of genetic admixture was detected among Anatolian Black, Turkish Grey Steppe, South Anatolian Red, and South Anatolian Yellow, whereas East Anatolian Red and Zavot were distinct from the other native and cosmopolitan cattle breeds. TreeMix algorithm under the assumption of one and two migration events revealed a migration route from Anatolian clade to Anatolian Black, while a second migration edge was drawn from Brown Swiss to East Anatolian Red. This study demonstrates the importance of national conservation studies in the native breeds whose population size has dramatically decreased. In addition, SNP arrays and next-generation sequencing platforms are recommended for future studies to reveal the genetic variation of other local Turkish livestock species to arrange effective conservation programs.

This study aimed to reveal the genetic variability of mitochondrial DNA (mtDNA) displacement-loop (D-loop) region in 62 animals belonging to three native Turkish cattle breeds, namely Anatolian Black (AB), East Anatolian Red (EAR) and Zavot (ZAV), and to conduct phylogenetic relationship analyses to obtain deeper information on their genetic origin and breeding history by comparison of 6 taurine and 11 indicine breeds, together with 66 polymorphic sites, a total of 31 haplotypes, of which 15, 10 and 6 were detected in AB, EAR and ZAV, respectively. Mean nucleotide and haplotype diversity were 0.01 and 0.891, respectively, whereas the genetic differentiation derived from Wright's F_ST index was 0.174 across the breeds. A significant level of total variation (17.42 %) was observed among breeds in molecular variance analysis. Six main haplogroups (T, T1, T2, T3, Q and I2) were detected in Anatolian cattle populations, where T3 was the most frequent among breeds (43.55 %), whereas I2, an indicine specific haplogroup, was observed only in ZAV. At the breed level, phylogenetic analyses supported by 198 sequences of 17 cattle breeds and 3 outgroup species retrieved from the GenBank clustered native Turkish cattle breeds with the taurine group rather than the indicine one, as expected. However, indicine admixture at low frequency (8.89 %) was detected in the ZAV breed for the first time due to more likely gene flow from indicine cattle breeds raised in neighbour countries, particularly Iran. This finding should be further investigated in all native Turkish and indicine cattle breeds from nearby countries to clarify gene flow and indicine admixture in Anatolian cattle.

Next-generation sequencing (NGS) technologies have revolutionized livestock genomics by enabling rapid, high-resolution genotyping of local populations with thousands of single nucleotide polymorphisms (SNPs), offering unprecedented accuracy and cost efficiency. This study presents the first comprehensive genomic assessment of the Denizli (DNZ) and Gerze (GRZ) chicken breeds, comparing them to commercial broiler and layer hybrid lines using the double digest restriction-site associated DNA sequencing (ddRADseq) technique. A total of 94,208 bi-allelic SNPs were common between DNZ and GRZ, while 33,284 SNPs were retained among all populations after the quality filtering process. Genetic diversity parameters were higher in native Turkish chicken breeds compared to hybrid lines in which minor allele frequency (MAF) was higher than 0.3 in DNZ and GRZ while it was lower than this value in commercial hybrid lines. Notably, DNZ displayed the highest observed (0.386) and expected (0.375) heterozygosity, whereas the broiler hybrid line showed the lowest heterozygosity (0.254), suggesting inbreeding depression (FIS = 0.241). The negative inbreeding coefficient values occurring due to random mating were observed in DNZ and GRZ chicken breeds, while this value was estimated at 0.118 in the layer hybrid line. Population structure analyses such as principal component analyses (PCA), genetic distance-based neighbor-joining (NJ) tree, ADMIXTURE, and TreeMix algorithm revealed that DNZ and GRZ were genetically distinct from both each other and commercial hybrid lines. The results of this study confirm that comprehensive conservation strategies are efficient approaches to keeping genetic variability at an optimal level without inbreeding. Moreover, this study demonstrates the efficacy of ddRADseq in generating high-throughput genotypic data, providing a cost-effective framework for genomic diversity and population structure studies in indigenous chicken breeds.