The fermented beverage made from mare’s milk in Central Asia is called kumis. It is a traditional dairy drink of the Eurasian steppes, especially associated with Kazakh, Kyrgyz, Mongolian, Bashkir, Kalmyk, and Yakut communities.
Kumis is made by fermenting raw, unpasteurized mare’s milk for hours or days. Lactobacilli bacteria acidify the milk, while yeasts convert some of its sugars into alcohol and carbon dioxide, giving the drink a tart flavor, mild alcoholic strength, and gentle carbonation. Its alcohol content is commonly about 0.7–2.5%.
Kumis is related to kefir, but the two are not the same: kefir traditionally uses solid kefir grains, whereas kumis uses a liquid starter culture. Mare’s milk contains more lactose than cow’s or goat’s milk, which helps fermentation. Traditional production used horse-hide containers that were periodically churned or agitated.