Bovine, Ovine, and Caprine RANKL (Receptor Activator of Nuclear Factor κB Ligand, also known as TNFSF11, TRANCE, or OPGL) is a cytokine belonging to the tumor necrosis factor (TNF) superfamily, which includes related ligands such as TNF-α, Fas ligand (FasL), CD40 ligand (CD40L), and TRAIL that regulate immune signaling, cell survival, and apoptosis. In cattle (Bos taurus), sheep (Ovis aries), and goats (Capra hircus), the RANKL protein is identical at the amino acid level, reflecting strong evolutionary conservation and indicating similar biological functions across these ruminant species. RANKL is expressed primarily by osteoblasts, stromal cells, activated T lymphocytes, and other immune cells, and it binds to its receptor RANK (receptor activator of NF-κB) on osteoclast precursors and mature osteoclasts. This interaction activates intracellular signaling pathways including NF-κB, MAPK, and NFATc1, promoting osteoclast differentiation, activation, and bone resorption. RANKL activity is tightly regulated by osteoprotegerin (OPG, TNFRSF11B), a soluble decoy receptor that binds RANKL and prevents interaction with RANK, thereby controlling bone remodeling. In ruminants, RANKL signaling is important for skeletal development, bone turnover, and calcium homeostasis, particularly during physiological states such as growth, pregnancy, and lactation, when mineral metabolism is highly regulated. Because bone metabolism and mineral balance are critical for livestock growth, reproductive health, and dairy production, bovine, ovine, and caprine RANKL is studied in research on bone biology, osteoclast regulation, and metabolic disorders affecting skeletal health in ruminant species.