Advances in Equine Genomics: Decoding the Genetic Architecture of Morphology, Performance, Behavior, and Adaptation.

The genus Equus, encompassing horses, donkeys, and extinct relatives, has evolved over approximately 55 million years from small, multi-toed ancestors to the modern horse. Selective breeding has produced over 600 distinct horse breeds optimized for diverse traits such as size, conformation, performance, and adaptability. In the past two decades, rapid advances in equine genomics have significantly deepened our understanding of the molecular basis of these traits. The integration of high-throughput sequencing, genome-wide association studies (GWAS), and single-nucleotide polymorphism (SNP) genotyping has revealed key genes and genomic regions associated with body size, coat color and texture, performance, behavior, and environmental adaptation. Variants in genes such as MC1R, ASIP, KIT, PAX3, and KRT25 govern pigmentation and coat characteristics, while DRD4, COMT, and SLC6A4 are associated with behavioral attributes like trainability, fear response, and sociability. Athletic traits arise from complex genetic interactions affecting muscle composition, gait, speed, and stamina. Furthermore, genomic studies highlight adaptations to diverse environments, including hypoxia tolerance, heat resistance, and endurance in harsh terrains, demonstrating the species' remarkable plasticity. Collectively, these findings emphasize how evolutionary processes and human-driven selection have shaped the genetic diversity, adaptability, and enduring success of equines across ecological and functional landscapes.