Any milk I had while in the Mongolian countryside was boiled first.
Also, is airag safe to drink, at least from an infectious disease perspective?
The following suggests that airag can give you diarrhoea:
The national drink of Mongolia is also a staple in celebrations,
though it's slightly less alcoholic and more...unique. Known as Airag,
this is a summer seasonal drink made from fermented mare's milk. It
is, to put it mildly, an acquired taste. At first, it feels like
you're drinking milk that's gone bad, but rest assured, 3 million
Mongolians can't be wrong, it is drinkable. Be sure to get a small
amount or ask for a taste before you get a whole cup, drinking too
much, when you're not used to it, might give you diarrhoea.
Ironically, I didn't get diarrhoea from drinking airag in Mongolia, but got it a few months later after having lassi in an Indian restaurant while on holiday in Orange in my home state of NSW, Australia. At least with airag, if you're old enough to drink it, you're old enough to hopefully not get killed by it.