Posterior pituitary releases a hormone named oxytocin (OT) that causes contraction of smaller ducts and myoepithelial cells surrounding the alveoli of mammary glands. The milking process is allowed to be managed by an exogenous OT by its vital role in neuro hormonal milk-ejection process. OT increases milk yield by ↑ gland output, which is not due to residual milk removal. OT also improves the persistency of lactation. Receptor blockade of oxytocin causes milk ejection inhibition. OT injections cause increased OT blood levels which results in the prolonged myoepithelial and alveolar contractions that ultimately increase milk yield. Milk composition especially protein, fat, lactose and mineral concentration are influenced by exogenous OT administration. It affects the cell maintenance and mammary metabolism along with its proven physiological role in the milk ejection reflex. OT effects are not manifested through effects on cell remodeling. Observed effects of OT administration on reproductive anomalies are anestrous, the development of corpus-luteum cysts, follicular ovarian cysts, delayed age at puberty, repeated estrous cycles, dystocia, abortions, dead fetuses and retention of the fetal membranes. OT administered exogenously or secreted endogenously, establishes in minutes the desired effects and metabolized to inactive products rapidly in the body. Irrespective of whether OT is ingested with milk or secreted into the milk, it is degraded readily by gut-enzymes so that it doesn’t reach the circulation in biologically-active form so there seems to be less or no harm in consumption of milk from OT-treated-animals. But OT has remarkable effects on milk quality, composition and reproductive health of the dairy animals so it’s use in dairy industry should be discouraged.