Forgot to add, there has not been any fertilizer or pesticides used in the area she was in for at least 5 years.
Ingesting a toad would do that....
Couple of suggestions:
1) Search “neurotoxin symptoms of dogs”. You will find most of what you just described your dog having. The next question is what exactly is she getting into.
2) Go to a petcare/veterinary website and search for dog neurotoxins. Your dog might be ingesting some sort of mushroom or other plant either directly or indirectly (by eating a rodent that has eaten the plant). Hay itself can have various rusts and fungi. Has it been unusually wet before the is problem started?
3) Don’t let your dog run in that field until you sort it out. Even if you do, you probably can’t do anything to round up every plant or critter. It’s quite possible that each episode causes more damage, and that some substances might build up in her system, doing fatal damage.
I give my animals liquid silver biotics and also the silver ASAP gel. All by American Labs.