When two or more animals collide (or are touching) in water, and the player moves more than 16 blocks away from them, there is a massive FPS drop. However, when the sound is off this issue does not occur.
How to Reproduce:
Make sure sound is set above 0%! Dig a 1x1 hole 2 deep. Place water in the bottom. Spawn two or more chickens (more will make it worse) in the hole. Walk 16-18 blocks away, while observing FPS and sound CPU usage on the debug chart.
Attached is a video of reproducing the bug.