What you're looking at is the sound spam problem. And depending on the size of the space you're holding those poor chickens in, they could also be producing a massive amount of hit-box checks. I encourage you to build a machine which'll keep the number of chickens to a reasonable number and your problem will vanish.when do u start lagging normaly, i had 1000 chickens and that was too much even though i have pretty decent computer, normal?
how can u improve that? if my base gets bigger and and have a few more chunk loaders my max would be reached fast.
Updating LWJGL can help but it is still very noisy.
I'd love to know what you had 1000 chickens, as that may be part of the issue. Are you attempting to product a machine that can automatically make cakes, and send them to you via an ender chest? Perhaps you are stocking up a massive egg cannon?
500 skeletons is usually enough for my computer to start becoming sluggish, and my computer is fairly modern, so I'd say it is a "normal" level of slowness. Good luck!