Cow
From Memory Alpha, the free Star Trek reference
A cow is an Earth mammal used in agriculture, primarily for its milk. Cows are also rasied to be slaughtered and eaten.
In 2376, Tom Paris turned Harry Kim's holodeck date, Maggie O'Halloran, into a cow as a prank, unknowingly causing the people of the Fair Haven holoprogram to believe that Paris and Kim were evil spirits. (VOY: "Spirit Folk")
