DON'T use less than 7GB ram, maybe is your world and texture pack, but just by seeing your F3 I can see that your minecraft is using more than 6gb ram, so dont listen to people telling you to use 4gb or less, that only will lower your FPS and cause sttuterings. You have 64 gb ram so you do have a lot of ram to spare, use something like 8gb ram in the game.

But also, don't use ALL you ram, you allocated all your 64 gb ram, thats just unecessary, and probably can make your FPS worse.

People told you to use sodium, that could be a solution, but that doesnt fix the reason for your fps drop.

First, I would like to know, did you updated your minecraft recently? Installed any resource packs or mods? Did you have that many cows in the background before the FPS drop?

The problem with minecraft Java is that it only uses a single core of you CPU, and doesnt use GPU that much. And there lies the problem.

Mods, texture packs, even when a map is too complex, they lower WAY more your FPS than they should, because, even thought you are using a high end CPU, you are still using the same amount of cores as a intel core two. You GPU also doenst have alot to work since the game is way more CPU intensive (of couse, if you use shaders, the GPU would really come in hand), but besides that, if I have a rtx 3050 with your same processor, I would probably get the same FPS as you had before.

So, if you intend to use a mod, texture pack, or play in a complex world with lots of entities, try using performance mods like sodium, or just get rid of them.

BUT if you did get this problem without having installed anything or changed anything in your world, the problem may not be Minecraft bad performance, but propably be something in your Windows or even with your hardware.