I have created an identical world in both version 1.7.10 as well as snapshot 14w32d. Both on creative mode. It would seem that the new rabbits have taken the place of almost all horses in this seed. Horses now seem to be very rare and almost non existent. I encourage you to look in as many plains as possible to see how widespread this seems.
Here is the seed I used: 1630353705672252276
Here are the coordinates of a plains biome to verify this: x: 968 Y:72 Z:-255
Screenshots attached.
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.