»[survival] how to make sheeps not despawn?

hi, so i've been trying to make a wool farm by having all sheeps from a different color. My problem is when I am close to completing them the message about clearing entities come up and apparently more than half of my sheep are despawned in the process. is there any way to prevent this? like by using name tag on my sheep? thanks

 

There's a limit of 8 entities per chunk. If you had more than 8 sheeps crowded within a chunk, chances are entity clears will despawn the excess. Try spacing your sheeps out across different chunks

 

You can make many farms
but make sure that they aren't close to each other like this
Farm-----------------Farm------------------Farm-----------etc...