Put the summary of the bug you're having here

Lag should not appear outside the pen of rabbits and surrounding rabbits.

Client wasn't lagging however the rabbits started lagging outside pen. Other mobs did not lag.

Steps to Reproduce:
1. Make a small very small pen of fence. 4x3
2. Spawn about 300 rabbits
3. Spawn 10 rabbits outside pen.
4. Should see rabbits become slow and almost sence lag (not on client.)