There are an abundant amount of them in the plains biome. Reason? Cows spawn anywhere near grass. The plains biome has a lot of grass. Good luck!
Cows mostly spawn in the Snowy Biomes, so what seed you have shouldn't matter.
As of Pocket Edition 0.3.0, cows have been part of Minecraft Pocket Edition. If you have that version or above, then there should be cows.
To get cows to follow you in Minecraft PE you need to have wheat in your hand.
Forest biomes of all types, try the tropical forest as well.
Mostly, they can be found next to lava.
Grass
Amost everywhere in India. Mostly in Punjab, Haryana, Himachal pradesh etc.
All the normal animals like chickens and cows can be found as well as ocelots in a jungle which can be tamed to be as cats.
Magma Cubes are found in the Nether, mostly around Nether Fortresses.
Cows fall from minecraft!
Leather is harvested by killing cows.
Holstein-Friesian are the most popular breed of cattle found. Many farms keep these milk cows.