2,4 D toxicity?

Question:Is 2,4 D toxic for long time if it gets onto a haystack?
just found out neighbor is spraying 2,4 D and last fall i had two ponies die within a week of each other - fall down, unable to get up and died within hours? First to die was the smallest, the the next bigger one. Can find info for grazing withholding but not for if it gets onto already cut grass (haybales) Hoping to find out before i have have to feed from the stack !

Answers:
sue your neighbor