Pigmen agrow cause intense lag 1.9

I have build a pigmen farm to get some XP and Gold and when i got agrow from them , it cause insane lag and the server stop and message in console is:

Can't keep up! Did the system time change, or is the server overloaded? Running 2528ms behind, skipping 50 tick(s)
A single server tick took 60,00 seconds (should be max 0,05)
Considering it to be crashed, server will forcibly shutdown.

video to demonstrate the bug : https://www.youtube.com/watch?v=ozmEIX2AGGM