There is No Cow Level

[420]

Well, there usually is no cow level. However, from May 15-21 there will be one accessible in the Act 1 area The Wilds.

http://us.battle.net/d3/en/blog/19083832/debunking-the-cowspiracy-5-14-2015

-420

[420]

If you go to the page linked above and click on that face with the glowing blue eyes at the top center you can see a video of the event. It's a Cow Goblin that spawns in random areas (like any other gob) and opens a portal to the cow level.

-420

[cuchulann]

Found it. Not a very large area but it is packed full of cows, and chests. Also the health globes that drop are t-bone steaks, yum!