[Theoria]

Kumis/airag is easier on people who are lactose intolerant. Horse milk in general will give ya the runs. Bigly.

[familyop]

Yep.

All Mongolian Recipes
Airag
Fermented Mare’s Milk
(often known by its Russian name “Kumys”)
https://www.mongolfood.info/en/recipes/airag.html
[Excerpt:]
“Fermentation destroys the lactose in milk, converting it into lactic acid, ethanol, and carbon dioxide. This makes Airag acceptable for lactose intolerant people, which includes many Mongolians.”