Oxytocin is a neurohormone produced in the hypothalamus that acts primarily as a neuromodulator in the brain and central nervous system. Oxytocin is synthesized in many organs other than nervous system that included the pancreas, thymus, adrenal gland, testis and ovary, and is known to exert paracrine function in these tissues. It is released in the systemic circulation to exert multiple central and peripheral functions, including milk ejection during lactation, uterine smooth muscle contraction during labour, control of social and sexual behaviours, regulation of natriuresis and control of cardiovascular homeostasis. This book focuses on the use of oxytocin in dairy practice, where oxytocin injections are administered to cattle before milking to cure disturbed milk ejection caused by reduced oxytocin release. Oxytocin is administered at supraphysiological dose to facilitate removal of residual milk. This book demonstrates the effects of regular administration of oxytocin on animal physiology, milk composition, plasma cortisol and insulin; and will add new research and knowledge to the hazardous effects of oxytocin that it contributes to the lactating animals.