Home > Crops & Livestock > Livestock > Horses > Pasture and Forages > Toxicants in Feeds, Hay and Forages [Image: Baling alfalfa hay] Conscientious owners should be aware that there can be potentially toxic substances in feeds. Poisonous Plants for Louisiana Livestock in the Fall [Image: Senna occidentalis] Images of major poisonous plants are presented to assist livestock owners with plant recognition. Toxic effects are also mentioned. Digestive System A horse has an unusual digestive system and its needs differ because of its athleticism.