Beware of Poisonous Trees in Pastures

With all the unsettled weather we have had lately, a word or two of caution may be in order regarding protecting horses from potentially poisonous plants they may encounter after a storm, particularly a storm that blows trees down. Wild Cherry and Red Maple trees are common across the southeastern United States, growing naturally in forested areas and along fence rows.  Most of the time, these trees provide a lot of shade, for which our horses are grateful during the hot summer months.  However, if a Cherry or a Red Maple tree gets blown down during a storm, suddenly the our horses are served a new dish of leaves that they find pretty tasty.  In this case, though, those tasty leaves are also pretty deadly. 

Cherry tree leaves, seeds, and buds contain cyanogenic glycoside and amygdalin.  Wilted wild cherry tree leaves, like those on a blown-down tree or broken limb, are highly toxic and can kill horses if they eat the parts of the tree that contain the poison.  The cyanide potential is greatest three to four days after branches have been broken off or blown down. Horses can show signs within an hour of eating wilted leaves. Clinical signs include severe respiratory distress, even sudden death.  Dry leaves are not hazardous to horses.

Red Maple leaves cause a significant breakdown of red blood cells when too many are eaten.  Treatment is extremely difficult, expensive, and largely unsuccessful. Horses will eat leaves from trees or branches that get blown down, or will eat wilting leaves that fall into or get blown into the pasture.  Clinical signs, which include weakness, depression, increased heart and respiratory rates, dark red urine, yellow colored mucus membranes, occur one to three days following ingestion of leaves or bark. The breakdown of red blood cells is a cause of death.

Consider the formula of lots of rainfall = looser soil around the tree roots.  Add in high wind velocities, and conditions are right for trees to get blown down.  Just be aware and check pastures next to wooded areas to make sure that there are no trees blown down.  If there are, don’t let the horses near until it has been verified that the blown down tree(s) are not Wild Cherry or Red Maple.  By the way, in addition to removing blown-down trees, be sure to bring along the fence-mending tools.  Trees that get blown down during a storm almost always fall across a fence.

Dr. Richard Mansmann of the NCSU College if Veterinary Medicine has a paper titled “Stupid Trees to Have Around Horses” that folks may want to take a look at for more information.

Red Maple Leaves in their Fall Color

Wild Cherry in Bloom.