Consumption of nightshades (from the Solanaceae family) is toxic to horses. Nightshades are a large group of plants which contain a variety of toxic alkaloids which are known for their adverse effects on the horse's nervous system and digestive tract. The two toxins which most frequently affect horses include glycoalkaloids and tropane alkaloids. Nightshades can present as small trees or small, weedy, erect shrubs. Many have white to purple flowers which produce round, fleshy, green berries that mature into a yellow or black color.

What Are Nightshade Plants

Common nightshade species that are often responsible for poisonings include Carolina horse nettle (Solanum carolinense), Hairy nightshade (S. physalifolium), Silverleaf nightshade (S. elaeagnifolium), Black nightshade (S. nigrum), American nightshade (S. americanum), and Jimsonweed (Datura spp). There are more than 70 species of native and introduced Solanum spp in North America alone. Nightshades are poisonous in both fresh and dried form, and sometimes are found in contaminated hay from a variety of grass species. They can also contaminate grain and grass cubes.