Reproductive system of animal is very easy but its difficult to understand the normal and rhythmic physiological change due to hormone. Its true that without proper health and nutritional status an animal can't yield a good animal. So modern theriogenologists are heart and soul trying to develop the reproductive performance from grass level.There is general agreement among animal scientists that the single most important cause of economic losses in the animal industries is reproductive inefficiency. The new advanced technologies and advance knowledge about reproductive hormones described in this book have the potential to add to the desired developments in farm animal reproduction. Further developments in advanced reproductive technologies is the hour of need as the farm animals offers greater future potential for economic development. These knowledge about reproductive hormones will be valuable research tools enabling scientists to gain deeper understanding of livestock reproduction.