Horsetail (Equisetum arvense) is not poisonous to dogs, but is toxic to livestock. Sheep, goats and cattle exhibit signs of poisoning after eating fresh horsetail. Ingesting dried horsetail leads to poisoning in horses. Signs of horsetail poisoning are weakness, weight-loss, clumsiness, breathing difficulties and in severe cases, death.
About this Author
Amy Deemer began her writing career in 1992. She began writing online content in 2009 and writes primarily for Answerbag and Garden Guides. Deemer enjoys researching and writing about flowers, plants and gardening. Deemer has an Associate of Arts in liberal studies from Westmoreland Community College.