You're probably well aware of the dangers ornamental yews and red maple trees pose to your horse, but some common fruits and vegetables can also be toxic. If your horse were to go foraging in your garden, which of the following produce has the potential to poison him?
POP QUIZ ANSWER:
All of the above!
Each of these plants, if eaten in sufficient quantities, is potentially toxic to horses. The leaves and fruit of the Guatemalan avocado (not the smooth-skinned Mexican variety) contain a still-unidentified toxin that can cause congestive heart failure and swelling of the lips, mouth, head and neck leading to respiratory distress. Eaters of large quantities of onions might develop Heinz body anemia, the same disorder that affects--and usually kills--horses who feed on red maple leaves. Ingestion of a few wild onions along with pasture grass won't produce this fatal anemia. The leaves of potato and tomato plants contain alkaloids that cause central-nervous-system stimulation followed by depression, weakness and sometimes colic and diarrhea. A ripe potato or tomato won't poison a horse, but green, rotting or sprouted fruits and roots contain those dangerous alkaloids.