No cows in minecraft pe world

Solution 1:

You need to be in a plains or forest biome in order for them to spawn, a rain forest biome doesn't work. If you are looking at a desperate resource for milk you can always use spawn eggs to bring in cows and pigs.

Solution 2:

If you're on survival then I'm afraid that you can't spawn them easily. I've heard that you create a large room then put fences around inside the room, cover the floor with torches then they should spawn. But I don't think it works(I haven't tried). The way I do it is make a world on creative, choose the cow egg, touch the ground where you want the cow then go to the chat and type in /survival. Once you've done that you'll need to make a bucket then hold it on the cow for a second, your bucket should automatically become a milk bucket. Hope that this helps!