Do cows understand dancing? Because in this video:
https://is-the-cow-video-bad.tumblr.com/post/673758901271986176/pretty-typical-dairy-calf-set-up-these-babies-are
I noticed that the calves seem to jump side to side while looking at the keeper. Your addition of "They seem happy" implies that this isn't an aggressive behavior, so what are they doing?
Cows jump around as a sort of playbowing behavior so based on that and my own experience dancing around my cows like a weirdo that would be my guess