That's right: a male cow. Either:
There is a precedent. In the mid-90s, there was an ad campaign for Boddington's (a newly plasticised version of what had once been a fairly decent beer) which featured an animated male cow. They were pretty funny, actually. Example: http://www.youtube.com/watch?v=95sC_DNTZFI
Or maybe the studio deliberately emphasised the maleness of the cow as to avoid the various Falwells of Middle America calling for boycotts of their "lesbian-biker-cow" film?
You left out d) that the immoral, Godless Hollywood wants to advance the homosexual agenda by feminising male animals.