A way to keep animals from escaping in minecraft

[coolthxmcdoom]

So, recently on the minecraft server, a few people were saying that all of their animals had escaped from their farms, even though their farms were completely fenced in. Since I have had problems with my animals escaping before, I decided to test a bit and figure out the best way to keep animals in their pens.

After testing a few different methods I read about, such as making the fence taller or to place blocks on top of the fence, only one method seemed to keep all types of animals in with little to no escapes.

The method is to simply make the animals pen area one block lower than the blocks the fence is on. This may sound kinda strange but I've tried it on two separate farms (one with different pens for each animal) and so far none have escaped.

I'm still not completely sure why this works, but I believe that it has something to do the fact that the animals no longer jump repeatedly into the fence.

Here's a few examples of the way the fence is placed:

My Farm:
http://i.imgur.com/mvGkO.jpg
http://i.imgur.com/6sTLZ.png
http://i.imgur.com/Wi0Li.png

BloodyIron's Farm:
http://i.imgur.com/L4iQn.png