Leptin is an adipocyte-specific protein that junctions as an ad ipostat. Leptin is impli cated mainly in the regulation of feeding behav iour and the. hypothalamic pituitary adrenal axis ( HPA). Leptin correlate closely with the degree of adiposity and decrease acutely w ith caloric restri ction. In this study , we tested the bov ine leptin expression in different tissues of cows using RT-PCR analysis. Moreover, bovine leptin cloning and purification was carried out throughout this study. The obtained results indicated that bovine lepti11 was highly expressed in the adipose tissue mammary gland and not ex pressed in any other organs tested. Also bovine leptin was cloned into pGEM-T easy vector and expressed into expression vector then transfected into expression host cells. The protein jrom the induced cells was purified and confirmed using western blot anal ysis and SDS-PAGE. The results in this study suggest that bov ine leptin besides its role inther egulation of energy homeostasis play s a role in mammary gland growth and de velopment