In the old Confederacy, terran marines were mostly criminals or rebels who had undergone mandatory neural resocialization. Freed from any previous allegiances or ideologies, these fearless soldiers stood ready to defend Confederate interests with their lives but exhibited an annoying tendency toward petty larceny, vandalism, and occasional cannibalism. Confederate authorities were unable to requisition enough reliable troopers in this way, and eventually recruiters turned to a new source of fresh meat for the grinder.
The obscure planet of Azeroth was found to harbor a dizzying selection of humans, mutants, and aliens in a state of perpetual superstition and conflict. The most physically imposing of these warrior races were the so-called 'tauren,' an anthropomorphic bovine genotype with super-human stamina, overpowered racial combat abilities, and bizarrely well-developed horticultural skills.
While most tauren were satisfied with their agrarian culture and primitive existence, the Confederacy was able to lure away large numbers of young bulls for a life of adventure and violence along the galactic rim. Other tauren referred to these adventurers as 'mad cows,' and they were ostracized from the rest of their kine. The newly created tauren marines didn't care--they got neat-looking armor and big guns to own everyone else with. These beefy new soldiers are now an integral part of the Confederate military, and have managed to horn in on the roles traditionally filled by firebats and other infantry units.
http://www.starcraft2.com/features/terran/taurenmarine.xml
