In summer, women milked the mares, sometimes as often as eight or nine times daily. Much of the milk was allowed to ferment, producing an alcoholic drink known as airag (or koumiss).
Some of the Mongol Khans and members of the elite consumed vast quantities of liquor, including airag, prompting one scholar to attribute the fall of the Mongol Empire in part to the increasing problem of alcoholism among its leaders.
Contemporary Mongolia continues to face a high incidence of alcoholism.
"Dietary Decadence and Dynastic Decline in the Mongol Empire," by John Masson Smith [PDF], in Journal of Asian History, 34/1 (2000). Reprinted with permission from publisher, Harrassowitz Publishing House.