author(s)
Prasanna Pal, Satarupa Ghosh, Sonika Grewal, Jyotimala Sahu and Anjali Aggarwal

abstract
During lactation, milk production starts increasing until the animal reaches peak yield and thereafter starts declining. So, a better production can be achieved if the animal has lactation persistency i.e. the ability to produce milk at a relatively constant level throughout the lactation. It actually depends upon the mammary cell population and their secretory activity. If these are maintained properly, the animal can continue production for a longer period. Several factors especially hormones affect the proliferation and death of these cells and also their secretory activity. Hormones like growth hormone, insulin-like growth factor-I, thyroid hormones, cortisol, prolactin, insulin, progesterone, estrogen and oxytocin play a major role. So, the objective of this review is to discuss the role of the hormones in lactation persistency so that it can be improved and higher production can be obtained.