The Development of Horns in Bovidae and the Genetic Mechanisms Underpinning This Process

Horns in Bovidae, including bovines, sheep, and goats, are evolutionarily conserved cranial structures derived from cranial neural crest cells and composed of a bony core, dermis, epidermis, and keratinous sheath. Their development follows a shared trajectory across species, progressing through placode, fleshy, and mature stages. Genetic regulators such as RXFP2, FOXL2, HOXD1, and TWIST1 have been identified as pivotal determinants controlling horn morphogenesis, sexual dimorphism, and the polled phenotype. This review synthesizes current advances in the evolutionary origins, morphological progression, and genetic regulation of horn formation in bovines, sheep, and goats to provide a comprehensive understanding of horn formation and variation. These findings lay the groundwork for future efforts to manipulate horn traits through genetic selection or genome editing, with implications for animal welfare and breeding.