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Common groundsel Horsetail
Ergot |
A wide variety of plants may be poisonous to horses. Toxic plants grow in
most areas of the country. It is important for horse owners to develop the
ability to recognize poisonous plants in their own area, because some
horses will not avoid consuming them. Information concerning recognition
and management of toxic plant growth can be obtained from local
veterinarians and agricultural extension agents.
Some of the more common poisonous plants in the western United
States include the common groundsel, which can cause permanent liver
damage, and yellow star
thistle, which affects the brain. Oleander, a
common ornamental in the west, is highly toxic to horses, causing
convulsions, diarrhea, colic, irregular heartbeat, and death.
The yew, a common ornamental plant in many areas of the country, is
sufficiently toxic that consumption of only 3 or 4 ounces of the plant may
cause death by stopping the heart. Another common ornamental plant toxic
to horses is the horsetail, which can produce a deficiency of vitamin B.
Signs of horsetail intoxication include weakness, decreased appetite, and
loss of coordination. The seeds of a number of legumes, such as some beans
and peas, also can be toxic for horses. The clinical signs depend on the
toxin in the particular seed and may involve many organ systems. A variety
of sorghum plants, such as Sudan
grass, can cause incoordination and
staggering as well as bladder inflammation.
Ingestion of tall fescue by pregnant mares can result in a variety
of reproductive disorders, including abortion, difficulties during birth,
thickened or retained fetal membranes, depressed milk production, and an
increased risk of foal death. The problem with fescue is actually not the
plant itself but a fungus that grows on the plant. Identification and
removal of infected plants are necessary to prevent the disease. Pastures
should be replanted wit fungus-free fescue seed. Another disease-causing
fungus associated with plants ergot, which infects the seeds of a variety
of cereal grains and can cause abortion, gangrene (death and decay of
tissue, usually caused by loss of blood supply and subsequent invasion of
bacteria), and neurologic disorders. Another fungus, Aspergillums
flavus, produces a toxin (alflatoxin) in grains and peanuts, causing
decreased growth and severe liver disease.
In general, the signs of plant intoxication depend on the
particular plant and the amount of toxin ingested. Preventing exposure to
poisonous plants in the best defense against their toxic effects. If
consumption of a toxic plant is suspected, a veterinarian should be
consulted immediately. |
