Bovine IL-17A (Interleukin-17A) is a pro-inflammatory cytokine belonging to the IL-17 family that plays a critical role in host defense and inflammatory responses in cattle (Bos taurus). IL-17A is produced primarily by Th17 cells, as well as by γδ T cells-which are abundant in ruminants-and other innate lymphoid cell populations in response to microbial infection and inflammatory stimulation. It acts on epithelial, endothelial, and stromal cells to induce expression of pro-inflammatory cytokines, chemokines (such as CXCL8), and antimicrobial peptides, thereby promoting neutrophil recruitment and enhancing mucosal and barrier immunity. In healthy cattle, basal IL-17A expression is generally low, but levels increase during bacterial and fungal infections, mastitis, respiratory disease, enteric infections, and parasitic challenges. IL-17A has been implicated in immune responses to pathogens such as Mycobacterium bovis, bovine respiratory disease complex agents, and gastrointestinal nematodes. In veterinary and agricultural research, bovine IL-17A serves as an important biomarker of Th17-mediated immunity and neutrophilic inflammation, providing insight into host-pathogen interactions, vaccine responses, and inflammatory disease mechanisms in cattle.