Bovine Thrombopoietin (TPO) (also known as THPO or megakaryocyte growth and development factor, MGDF) is a hematopoietic cytokine that plays a central role in the regulation of platelet production and megakaryocyte development in cattle (Bos taurus). TPO belongs to the class I cytokine family, which also includes erythropoietin (EPO), granulocyte colony-stimulating factor (G-CSF), and prolactin, cytokines that regulate blood cell development through related receptor-mediated signaling mechanisms. Bovine TPO is primarily produced by the liver, with additional expression in the kidney, bone marrow stromal cells, and other tissues, and exerts its effects by binding to the c-Mpl receptor (MPL, CD110) on hematopoietic stem cells and megakaryocyte progenitor cells. Activation of the TPO receptor stimulates intracellular signaling pathways including JAK2/STAT, MAPK, and PI3K/AKT, which promote megakaryocyte proliferation, maturation, and platelet formation, while also supporting hematopoietic stem cell survival and self-renewal. In cattle, thrombopoietin plays an important role in maintaining normal platelet counts and hemostasis, and it contributes to recovery of platelet production following bone marrow stress, inflammation, or blood loss. Because TPO regulates platelet generation and stem cell maintenance, bovine thrombopoietin is studied in research on hematopoiesis, platelet biology, and bone marrow function, with relevance to understanding blood cell development and immune responses in livestock.