The bark, leaves, and berries of western juniper trees in Oregon can cause abortions in late-term pregnant cattle.

The percentage of the abortion-causing compounds varied from tree to tree in a location, as well as between locations across Oregon, but did not appear to vary across time.

Cattle producers who winter cattle in pastures with western juniper trees should take cautions such as denying late-term pregnant cattle access to these pastures, providing adequate feed and shelter, maintaining pregnant cattle in good body condition, changing calving schedules to late spring or early fall, and, if abortions do occur, seeking veterinary care for any postpartum complications.