|Spring Parsley (Cymopterus watsonii)
Spring parsley causes a severe "sunburn" or photosensitivity in sheep and cattle. The plant also is known as Cymopterus and wild carrot. Animals do not die from eating spring parsley, but losses occur when affected ewes or cows with blistered, sore udders refuse to nurse their young. Lamb losses often are high; calf losses usually are low.
Spring parsley causes primary photosensitization similar to St. Johnswort. This differs from other causes of secondary or heptogenic photosensitization such as that seen in bighead, caused by horsebrush. Hepatic photosensitization is caused by the inability of the liver to metabolize and excrete chlorophyll metabolites (phylloerythrin). The photoactive toxins in spring parsley have been identified as furocoumarins, xanthotoxin and bergapten.
Spring parsley is a perennial that grows 8-12 cm tall. It gets its name from the finely divided leaves that resemble parsley. Small white or cream-colored flowers are borne in umbrella-like clusters about one inch across. The plant has a long taproot. Spring parsley is a member of the carrot family. Plants are poisonous from early spring until they mature and dry in early summer.
Where and When It Grows
How It Affects Livestock
Cattle are affected if they are exposed to direct sunlight after eating about one pound of the green plant. White areas on the body become "sunburned". Cows refuse to let calves nurse. In severe poisoning, all the white areas of the body may blister, and animals may lose weight rapidly. Sheep and cattle recover gradually after they stop eating spring parsley.
Signs of Poisoning
How to Reduce Losses
Spring parsley can be controlled by spraying plants in the bud to early bloom stages of growth with an amine salt of 2,4-D applied at the rate of 1.0 kg per acre of acid equivalent. Follow all precautions for handling herbicides.