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
Spring parsley grows on well-drained soils, on rolling foothills, and with sagebrush, piñon pines, and junipers. It occurs at elevations of 1500 to 3500 meters. This is one of the first plants to begin growing in early spring. It flowers from late April to June and disappears by early summer. It is considered a noxious weed and often invades pastures and rangelands.
How It Affects Livestock
Sheep are affected if they are exposed to direct sunshine after eating as much as 200 gm of the green plant. "Sunburn" varies from slight to severe; blisters form on areas of the sheep's body not covered by wool. In advanced poisoning, all the white areas of the body may be affected. Ewes are especially susceptible to spring parsley poisoning during March, April, and May. It is one of the first spring plants to emerge, and ewes may eat it soon after lambing. The udder and teats become so painful that the ewe will not allow the lamb to nurse. Newborn lambs die of starvation and dehydration. Surviving lambs usually are stunted from lack of milk.
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
Ewes and cows may refuse to allow young to nurse
Scabs form after blistering
Reddening and blistering of exposed areas of the body (nose, udder, external
How to Reduce Losses
To reduce losses from spring parsley, keep sheep and cattle off infested ranges in early spring until other plants appear. There is no known treatment for light-skinned animals that are affected by eating spring parsley, but they recover spontaneously if kept in the shade.
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.