Genomic characteristics of performance traits and adaptation to heat stress in desert Barki sheep

Abstract. The Barki sheep is well adapted to desert conditions with intense solar radiation, low precipitation, and feed shortages. This review highlights advances in the genomic characterization of Barki sheep and outlines prospects for genetic improvement. Studies on the genomic architecture of their growth traits have identified multiple candidate genes, many of which overlap with those reported in other sheep breeds, suggesting the existence of shared biological pathways for growth regulation. Reproduction performance has been linked to genomic mutations in key loci, with limited evidence of polymorphisms in other genes, reflecting possible breed-specific selection pressures. Genomic studies have further revealed candidate genes related to milk production, although milk yield remains modest. Heat stress represents a major challenge for desert livestock, and the physiological responses of Barki sheep are evident through changes in the respiration rate, gas exchange, and breathing intensity. Candidate genes associated with heat tolerance are involved in multiple signaling and transduction pathways that regulate cellular and biochemical responses to heat stress, highlighting the strong adaptive capacity of the breed. Population-based genomic studies have shown that Barki sheep cluster closely with other Egyptian breeds but remain genetically distinct from exotic populations, underscoring their local adaptation. The considerable within-breed genetic variation provides opportunities for selection to improve lamb growth rates while maintaining moderate ewe size, lean meat, and heat resilience. Overall, genomic evidence indicates that Barki sheep represent a valuable model for climate-resilient livestock production. Owing to their unique adaptation to desert conditions and the availability of identified candidate genes for growth, reproductive performance, milk production, and heat tolerance, these genes provide a foundation for accurate genomic prediction. Future breeding programs should focus on their strengths to improve productivity while safeguarding their adaptive performance.