Egyptian Barki desert sheep are widely distributed along the northwestern coast and represent an important source of income for Bedouin communities. The breed is primarily valued for its adaptability to harsh desert conditions, but it also has several economically important traits related to reproduction and meat production and quality (Aboulnaga and Abdelsabour, 2023). Barki sheep are named after the city of Barka in Libya and are spread across the coastal zone of the Western Desert (CZWD). They are raised under an extensive system; graze on natural rangelands and bushes sustained by limited rainfall; and follow a transhumant management pattern, moving to neighboring cultivated areas seeking feed and water. The breed is well adapted to arid and semiarid conditions, enduring high temperatures, intense solar radiation, low precipitation, and feed shortages. Compared to other Egyptian breeds, this is a fat-tailed, coarse-wool sheep with good fertility and mothering ability but relatively low growth performance (Fahmy et al., 1969). Barki sheep are thus characterized by their ability to survive, reproduce, and maintain productivity under harsh desert conditions (Aboul-Naga et al., 2022). There is a pressing need to understand the genetic and genomic basis of these adaptive traits to improve their performance sustainably.

The development of molecular genetics and its associated techniques have facilitated deeper insights into the genetic mechanisms underlying livestock traits. Different approaches, including candidate gene approaches, genome-wide association studies (GWASs), and selection signature analyses, have been used to identify quantitative trait loci (QTL) related to economically important traits. The candidate gene approach targets genes thought to be responsible for a given phenotype, whereas GWAS and selection signatures identify putative genes or chromosomal regions across the entire genome that influence trait variation (Beuzen et al., 2000).

Barki sheep have been the focus of several scientific investigations aiming to estimate genetic parameters for economically important traits (Melak et al., 2019; Sallam et al., 2019), to characterize genes or single-nucleotide polymorphisms (SNPs) associated with performance traits (Aboul-Naga et al., 2021; Abousoliman et al., 2020), and to assess their genetic diversity relative to other sheep breeds (Kim et al., 2016; Mwacharo et al., 2017). Despite these advances, knowledge gaps remain in elucidating the genomic architecture and biological pathways underlying their adaptation. Previous studies have identified several candidate genes associated with heat tolerance and productive traits. However, the border genomic mechanisms and regulatory networks supporting these adaptations remain insufficiently characterized. Specifically, limited attention has been given to the interactions among genes, the functional roles of identified variants in shaping their physiological responses, and the genomic basis of reproductive efficiency under chronic heat stress. Furthermore, most published work has relied on single-gene approaches, underscoring the need for system-level genomic studies that can capture the complexity of their adaptive responses.

The study of Barki sheep genomics holds both economic and ecological importance for production in arid and semiarid regions. Climate change projections indicate rising temperatures and expanding desertification, emphasizing the urgency of characterizing the genetic basis of heat tolerance. The Barki sheep represents a valuable genetic resource due to its ability to sustain productivity under high thermal loads, efficiently utilize limited feed resources, and support the livelihoods of the pastoral and smallholder communities in marginal environments. Clarifying these genomic mechanisms in the breed can directly help in identifying breeding and conservation strategies across comparable dryland systems.

From an economic perspective, understanding the genomic basis of these adaptations could facilitate the development of genomic selection programs aimed at enhancing productivity without compromising adaptive traits, support the design of breeding strategies to introduce heat tolerance into other populations, and strengthen conservation efforts targeting genetic diversity threatened by climate change. Ecologically, Barki sheep raised under a low-input production system offer a sustainable model for livestock rearing in fragile ecosystems, highlighting the potential to balance food security goals with environmental stewardship.

This review addresses the urgent need to link genomic knowledge with climate adaptation in livestock. Advancing our understanding of the genomic foundations of adaptive traits in Barki sheep makes it possible to design breeding programs that not only increase food security but also safeguard the genetic resources crucial for long-term resilience in challenging environments. The outcomes are directly relevant for communities in dryland regions worldwide that depend on livestock as a primary source of livelihood and nutrition.

Several studies have investigated the genetic basis of growth performance in Barki sheep via diverse approaches, such as whole-genome sequencing (WGS), partial sequencing, single-strand conformational polymorphism (SSCP), and kompetitive allele-specific polymerase chain reaction (KASP) genotyping (Table 1). Collectively, these studies have identified multiple genes associated with birth, weaning, and 6-month weights, including ADRβ3, CLPN3, PRKAG3, CLPN, LEP, MSTN, EYA2, GDF2, GDF10MEF2B, SLCI6A7, TBX15, IG3, TFAP2B, TNNC2, CPXM2, IGFBP3, and GH (Saleh et al., 2022). Among these genes, the ADRβ3 gene has received particular attention. In this context, Ibrahim (2014) demonstrated its association with growth traits such as marketing weight and body measurements in Barki sheep, which is consistent with earlier findings in New Zealand sheep breeds (Horrell et al., 2009; Forrest et al., 2003). Similarly, the CLPN3 gene was reported to influence the birth, weaning, and marketing weights of Barki lambs (Shehata et al., 2014). This finding aligns with broader evidence linking an SNP in intron 11 of the CLPN3 gene to birth weight across different sheep breeds (Chung et al., 2007) and to retail meat cuts (Bickerstaffe et al., 2008).

Other genes have also been highlighted for their roles in growth regulation. The PRKAG3 gene is associated with pre-weaning gain, marketing weight, the muscle index, and the mass index (Ibrahim, 2015), whereas the CLPN gene influences birth weight, final weight, and average daily gain (Mahrous et al., 2016). The leptin (LEP) gene has emerged as a strong candidate for growth-related traits, with polymorphisms significantly associated with weaning weight and pre-weaning average daily gain (Abousoliman et al., 2020). Its well-established role in regulating feed intake and energy metabolism further supports its biological relevance (Tahmoorespur et al., 2010; Choudhary et al., 2005).

More recently, WGS-based studies have expanded the list of candidate genes. Abousoliman et al. (2021a) detected several potential candidate genes associated with weaning weight and average daily gain in Barki lambs, such as EYA2, GDF2, GDF10, MEF2B, SLCI6A7, TBX15, TFAP2B, TNNC2, CPXM2, IG3, TFAP2B, TNNC2, and CPXM2. These genes are functionally linked to key biological processes, such as metabolism, growth, organ morphogenesis, skeletal muscle development, and cell proliferation and differentiation, highlighting their potential as molecular markers across different sheep breeds. Additional evidence was provided by Saleh et al. (2022) and Ibrahim et al. (2023), who reported associations between the IGFBP3, GH, HSP90, AB1HSF1, ST1P1, and ATP1A1 genes and growth traits including birth, weaning, 6-month weights, and average daily gain.

Taken together, these findings demonstrate that Barki lamb growth performance is influenced by a complex set of genes with pleiotropic roles in growth, metabolism, and muscle development. The convergence of evidence across studies and breeds underscores the potential of these loci as genetic markers for improving prediction strategies in Barki sheep.

Barki sheep exposed to heat stress (HS) presented a significant increase in respiration rate (RR) and minute ventilation volume (MVV) and a decrease in tidal volume (TV) and gas exchange (shallow, rapid panting) (Elbeltagy et al., 2015b). Changes in RR and gas volume were more pronounced in terms of the incidence of deep breaths observed, whereas changes in thermal parameters were less detectable. Within the breed, medium-sized desert sheep appeared to be more compatible with the prevailing hot and dry conditions, highlighting possible interbreed variations in terms of heat adaptation. Consistent results were reported for Barki populations raised at different locations in the CZWD (Table 4).

At the genomic level, increasing evidence from several studies has highlighted the genetic variants and candidate genes that contribute to the remarkable adaptation of Barki sheep to HS (Table 5). Kim et al. (2016) identified 18 genes in two regions on chromosomes 6 and 12, each spanning one gene, CSN3 and PCDH9, respectively. In addition, seven candidate regions were identified across chromosomes 1, 3, 7, 10, 12, 13, 17, 19, and 21. Two of these regions, located on chromosomes 3 and 13, each contained a single gene (TRHDE and BMP2, respectively). In total, 119 genes were detected, many of which are involved in multiple signaling and signal transduction pathways regulating diverse cellular and biochemical processes. Genes under selection were linked to traits such as thermotolerance (FGF2, GNAI3, and PLCB1), body size and development (BMP2, BMP4, GJA3, and GJB2), energy and digestive metabolism (MYH, TRHDE, and ALDH1A3), and nervous and autoimmune responses (GRIA1, IL2, IL7, IL21, and IL1R1). Moreover, eight candidate genes with selection signatures were identified on a conserved syntenic segment on chromosome 10, providing strong evidence for natural selection acting in the Barki environment. Gene expression studies further support these genomic findings. In this context, Younis (2020) revealed that the expression levels of the HSP70 and HSP90 genes were downregulated in Barki sheep but upregulated in Aboud Leik southern local sheep. They recommended the use of HSP70 and HSP90 expression profiles as reference markers for selecting animals with improved adaptability in arid conditions.

Similarly, Aboul Naga et al. (2021) studied six genes associated with oxidative stress responses in different farm animals. The expression levels of these genes differed between low-tolerance (LT) and high-tolerance (HT) Barki sheep under exercise heat stress (EHS). While the SOD gene was expressed at lower levels in HT sheep, other genes (GST, CAT, HSP70, BLF, and LACT) were expressed at higher levels in HT animals than in LT animals. Aboul-Naga et al. (2022) reported that 46 SNPs are significantly associated (P≤0.001) with heat tolerance. These SNPs, located mainly between OAR7_60745094.1 and OAR7_60704536.1, had effects ranging from 0.57 to 1.47 units, either positive or negative. Gene ontology analysis revealed that the associated genes participate in calcium and manganese binding and/or transport, epidermal growth, and cell adhesion, with additional roles for epidermal growth factor (EGF)-domain-related genes, kinases, growth, and collagen-containing extracellular matrix proteins. Among the most significant SNPs were variants in the MYO5A, PRKG1, GSTCD, and RTN1 genes (P≤0.0001). Notably, MYO5A encodes a protein widely distributed in the melanin-producing neural crest of the skin. Further associations identified SNPs in the PLCB1, STEAP3, KSR2, UNC13C, PEBP4, and GPAT2 genes. The involvement of genes linked to pigmentation and tail fat deposition suggests a functional basis for why near-eastern sheep breeds outperform temperate breeds under HS in hot, dry environments. These findings further imply that climate change may drive shifts in livestock distribution in arid regions, favoring sheep over cattle and goats over sheep, highlighting the importance of utilizing local breeds naturally selected under desert conditions.

Additional evidence emphasizes the role of season-specific responses. Abu Rawash et al. (2022) reported nonsignificant seasonal differences in tolerance gene expression in Barki sheep. However, they reported summer upregulation of IL2 and IL6 alongside winter upregulation of HSP70, suggesting distinct roles; HSP70 is a molecular marker for cold adaptation, and IL2 and IL6 are involved in heat adaptation. These results illustrate that Barki sheep withstand HS by adjusting their physiological parameters while maintaining stable blood plasma constituents. In addition, Ibrahim et al. (2023) investigated the associations between Barki lamb performance and nucleotide sequence variations in growth- and efficiency-related genes (GB1CAST, GB2LEP, GB1MYLK4, GB1MEF2B, and GB2TRPV1). The SNPs identified for growth were strongly correlated with heat tolerance, indicating that selection for growth and heat tolerance may be achieved simultaneously. They recommended exploiting this genetic variance as a proxy marker for breeding Barki sheep resilient to both environmental stress and production demands.

Genomic diversity in Egyptian sheep has been investigated via both genomic and microsatellite markers, providing complementary perspectives on population structure. Studies based on genome-wide SNP data (Kim et al., 2016; Mwacharo et al., 2017; Aboul-Naga et al., 2022) revealed that Egyptian breeds tend to cluster closely together and remain clearly separated from the exotic breeds (Table 6). Within this broader pattern, Egyptian sheep were more closely related to western Asian fat-tailed breeds than to European breeds. The Barki breed was distinguished from other Egyptian populations, reflecting its unique genetic background.

Microsatellite-based studies (Elbeltagy et al., 2015a; Mahfouz et al., 2008; El Nahas et al., 2008; Sallam et al., 2012; Othman et al., 2015; Othman et al., 2016; Germot et al., 2022) largely support these findings while offering a finer resolution in terms of the relationships among local breeds. These studies consistently reported two main clusters: one comprising Ossimi and Rahmani sheep and another divided into two subclusters, with Barki forming one branch and Saidi and Suhagi forming the other. This pattern indicated that Barki sheep are genetically closer to Saidi and Suhagi than to Ossimi and Rahmani, which are closely related to each other. Within the Barki population, subpopulation analysis revealed two genetic groups: Hammam and Negila on one side and Matrouh and Salloum on the other. Despite these subdivisions, the overall genetic distances between subpopulations were limited, reflecting a good degree of genetic similarity. Together, these findings illustrate how both genome-wide and microsatellite approaches converge into a consistent picture of Egyptian sheep diversity while also highlighting the unique genetic profile of the Barki breed.

This review highlights the unique adaptive capacity of Barki sheep and combines current knowledge on their productive performance, physiological resilience, and genomic potential. Previous studies have largely provided descriptive accounts of breed characteristics; the combination presented here emphasizes the strategic role of Barki sheep in supporting livestock production in arid and semiarid regions. Despite their importance, research on Barki sheep remains fragmented, with limited genomic resources and few efficient evaluations of productivity–resilience trade-offs. Addressing these gaps is critical for designing effective breeding and conservation strategies. Integrating genomic tools with traditional selection schemes offers a promising pathway to accelerate genetic improvement while preserving adaptive traits that safeguard survival under climate stress. The evidence summarized in this review underscores the need for coordinated efforts to establish and expand the reference population, refine genomic prediction approaches tailored to performance and adaptive traits, and implement community-based breeding programs. These initiatives would directly strengthen the sustainable improvement of Barki sheep and offer transferable strategies for enhancing the resilience of other indigenous breeds in arid production systems.