My Dutch pig has a tumor on its neck.

It is normal for a pig to have a cyst on its neck. Almost every pig has it. When cysts get bigger, they will rupture. Then the pus inside will be squeezed out and the wound will heal. But your pig should be coccidiosis, a parasitic disease, which is usually undetectable and will only develop an hour or two before death. So it's hard to find. Now he has a seizure. It's too late to save it. I'm sorry for your loss. I hope the pig will live happily in heaven.