I know nothing about it, but I encourage you to investigate further:
Tansy Mustard
Toxic agent
The toxic agent is unknown. Large quantities of the plant must be consumed before poisoning occurs. Tansy mustard also accumulates toxic levels of nitrate. Cattle are the only kind of livestock reported to be poisoned. The first clinical sign is partial or complete blindness (blind staggers). Animals wander aimlessly until exhausted, or may stand pushing their head against a solid object for hours. Next, or along with blindness, comes an inability to use the tongue or to swallow (paralyzed tongue). Cattle may stand at water unable to drink, or try unsuccessfully to graze.
