I must say, that would be a rather interesting experience. Although I have heard there is a certain way to do it, or you just end up agitating the poor cow.
Needless to say, I never have. Despite my godparents owning a farm, and my grandmother living in a rural area, but I don't think she had room for a cow, so she had a pig running around.
I wouldn't mind giving it a try though, I'd probably end up laughing or hurting it. XD;