If you begin to believe you are a cow, then you are experiencing Lycanthropy : http://en.wikipedia.org/wiki/Clinical_ly...
..or you're just a troll
In either case, you should seek medical help. Species dysphoria can be associated with a need to "escape" and might be correlated to other mental illnesses. Trolling might be a result of the same thing, but there is not sufficient data on that subject.
Perhaps you were a cow in the past life
I must admit it would be nice to live care-free for a while
Yes I understand that it is weird but I think it would be so cool to live life as a cow. I want to know if there is a name for this or if I am the only person out there that wants to be a part of a different species.