It is moving onto rangelands. Poison-hemlock is found at roadsides, on edges of cultivated fields, along creekbeds and irrigation ditches, and in waste areas. How It Affects Livestock Poison-hemlock ingestion frequently is fatal. Sheep may be poisoned by eating as little as 100 to 500 gm of green leaves. Cattle that eat 300 to 500 gm may be poisoned.
Signs usually appear within an hour after an animal eats the plant.
Animals die from respiratory paralysis in 2 to 3 hours. Convulsions, which are common in western water hemlock poisoning, seldom occur with poison-hemlock. Skeletal deformities or cleft palate may be induced in offspring of cows, sheep, goats, and pigs that eat poison-hemlock during gestation. Susceptible stages of gestation when animals should not be exposed to this plant include 40 to 70 days in cows and 30 to 60 days in sheep, goats, and pigs. Palate and skeletal deformities in calves are indistinguishable from the lupine-induced crooked calf disease.