Furanocoumarins are found in all growth stages of the plant, when eaten fresh or dried in hay. The toxic dose of wild parsnip is not known. Severe sunburn (photosensitivity) occurs in livestock ingesting furanocoumarins if they are exposed to UV light after ingestion. Severe sunburn occurs on the white or other light skinned areas, but not the black, brown, or other dark skinned areas because melanin in the dark skin absorbs the UV light and prevents it from reacting with the furanocoumarins.

Treatment includes removing the plant source and moving animals to an area where shade is available. Topical treatments can be used for skin lesions resulting from the sunburn. People should wear gloves and long sleeved shirts if pulling or working around wild parsnip as they too can suffer sever sunburn from contact with wild parsnip.

Waterhemlock (Cicuta species) is a perennial weed that is commonly found in moist ditches (Figure 4). The plant is two to seven feet tall, with hollow stems that are branched at the top and often mottled with purple spots. Waterhemlock has white flowers that are borne in umbrella shaped clusters called umbles. Leaves have a lacy appearance and smell like parsnip when crushed. The tap root resembles a small white carrot.

Waterhemlock contains the short chain alcohols cicutoxin and cicutol, with virtually all cicutoxin and cicutol confined to the roots. Even though the concentration of cicutoxin and cicutol decrease after the plant dries, waterhemlock can still be toxic in hay. Root fragments can also be present in the hay if uprooted during the harvesting process. Death is reported in animals ingesting about two grams of waterhemlock root per kg body weight or about two pounds per 1,000 pound animal. Animals are most commonly found dead after ingestion of waterhemlock. Rarely, violent seizures are observed. Animals that survive for 8 hours after the onset of clinical signs are more likely to recover, unless they have complications from seizures. There is no specific antidote.