As fall approaches, it is important to remind horse owners about the dangers posed by leaves from some maple trees. Horse owners who board horses or have just found new stable accommodations may not remember to check on tree varieties. The green leaves from fallen limbs are also toxic as they wilt and dry.
Source: Equus, September 2016, page 30.
Wilted or dried red maple leaves are extremely dangerous to horses. They contain concentrated amounts of gallic acid and other identified toxins that cause Heinz body anemia, a breakdown of the red blood cells that prevents them from carrying oxygen. The kidneys, liver and other organs may also be damaged. As little as a pound or two of leaves can be fatal.