Type of animal spawns

Put the summary of the bug you're having here

What I expected to happen:
When I create a new world, I always like to have a small pig, cow and chicken farm. But this is not working very well in the 1.5.2 patch.
I expected that around me (maximum 1000 blocks range) are cows, sheep, pigs and chickens so I can make the little farms....*

What actually happened was...:
In normal and creative mode, there is always 1 or 2 kinds of animals unfindable. I restarted so many survival games just because I mostly can't find chickens. And if it aren't the chickens I can't find it are the sheep.

What I see in creative mode is that all animal spawns are 1 or 2 types of animals. I know chickens mostly spawn in a forest but with this patch that's not the case anymore. Now there are plenty of animals, but only 1 or 2 kinds.

Steps to Reproduce:
1. Just create a new world. ( there is a slight chance all animals close by, but 90% of the time they aren't. )