Space Cow

From Mass Effect Wiki

Space Cows are thin oxygen-breathing herbivores with four legs and two vestigial forelimbs.

There is no distinction between the sexes visible to players of the game, in particular no mammary glands. Either their females lie in hiding somehow, or else (more likely) the space "cows" are not mammals.

They naturally browse in herds. There are feral herds on Chasca, Nodacrux, and Ontarom.

Cows have a dialog option that does nothing. They are labeled as cows, by extension, from the Shifty Looking Cow at Ontarom.

[edit] Speculation on origins

The space cow planets are in the Maroon Sea and the Kepler Verge, both relatively near to each other on the same spiral arm. Each world has a history; turians from the Bostra Outpost landed on Ontarom while others from the Thracia Colony landed at Nodacrux (although these turians appear not to have settled them, and may not even have been aware of Chasca, where the Protheans settled long enough to leave ruins behind). Chasca is now being colonised by humans. The common thread linking all three worlds is the human ExoGeni Corporation: cataloguing Ontarom, supplying Chasca and involved at Nodacrux.

The space cows are arguably natives of Ontarom, domesticated and spread by ExoGeni to local systems in a characteristic display of budget, practicality and ecological salvage. If so, then they and the other wildlife on Ontarom have the same chirality as humans, and are inedible to turians and quarians.