believe they are yaks, but not the longhaired ones you see further up in the Himalayas.
Thanks for the pictures. I agree with radson. Those are definitely dzos rather than yaks.
If curious, it's easy to tell.
Now that I think about it though, I did see a yak in the Annapurna region. It was up at one of the Dhalagiri basecamps at the base of the Dhalagiri Icefall. That's a lot higher up than Marpha though.