There are many things horses should never eat. Certainly, toxic plants rank high on the list of things to avoid, but other substances, organisms, and chemicals can pose risks as well…American, English, Japanese, and Western yew are ornamental evergreen hedge-type plants that grow red berries in the fall. They are commonly used in landscaping across much of North America. As little as a mouthful or two of yew can be lethal, says Sarah Ralston, VMD, PhD, professor in Rutgers University’s Department of Animal Sciences. The plant’s alkaloid toxin taxine causes cardiac and respiratory failure, often within minutes. “It’s not uncommon for horses to be found dead with the plant still in their mouth,” Ralston says.