What I found interesting is the article in Wikipedia that mentions the following:
"Gardeners who use dung as fertilizer should check to make certain that the animal source has not grazed on picloram treated hay, as the dung still has broadleaf killing potency."
I know of a version of picloram (Tordon) as being used in Montana to control the noxious weed "Russian Knapweed." It is true that if horses ate in the area sprayed their fecal matter still had a herbicidal effect on other areas where the horses left their fecal matter. So we must be careful as to where we get our manures from.
"Learn from the mistakes of others, you won't live long enough to make them all yourself. One of them will be your last."