The mountain laurel, also called the mescalbean sophora, can be poisonous to cattle, sheep, and goats. The U.S. Forest Service Web site includes this statement: "Mescalbean sophora's seeds, leaves, and flowers are poisonous to cattle, sheep, and goats. Cattle are most susceptible to poisoning by leaves, while goats and sheep are more tolerant. Affected animals often recover if placed on a high-quality diet." The seeds have such a hard coat on them that if swallowed whole, they will pass through the digestive tract intact with no effect on the animal that ingests them. The seed itself is highly toxic and if chewed and swallowed can be fatal.
For more information, see the U.S. Forest Service Web site: www.fs.fed.us/database/feis/plants/tree/sopsec/all.html.