Animals going through fences

Put the summary of the bug you're having here

What I expected to happen was...:
Describe what you thought should happen here
Animals to not magically move through fences (lol)

What actually happened was...:
Describe what happened here
Animals magically moved through fences

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...Log in
3. ...Play (No mods or resource packs)