Chicken and Duck Basic Fibroblast Growth Factor (FGF2, also known as bFGF) is a heparin-binding growth factor belonging to the fibroblast growth factor (FGF) family, which includes more than 20 related proteins involved in cell proliferation, differentiation, angiogenesis, and tissue repair. In chickens (Gallus gallus) and ducks (Anas spp.), the FGF2 protein is identical at the amino acid level, indicating strong evolutionary conservation and suggesting similar biological functions across these avian species. FGF2 is produced by fibroblasts, endothelial cells, macrophages, and other stromal and epithelial cells, where it contributes to tissue development, vascular formation, and wound healing. FGF2 signals through fibroblast growth factor receptors (FGFR1–FGFR4) in the presence of heparan sulfate proteoglycans, activating intracellular pathways such as MAPK/ERK, PI3K–AKT, and PLCγ, which promote cell proliferation, migration, and angiogenesis. In avian biology, FGF2 plays important roles in embryonic development, feather follicle formation, and tissue regeneration. Because chickens are widely used as animal models for developmental biology, avian FGF2 has been studied in chicken embryo models of limb and vascular development, helping researchers understand growth factor signaling pathways that regulate tissue patterning and angiogenesis across vertebrate species.