Solanine concentrations can be high, especially in berries, and doses as small as 0.1 percent to 0.3 percent BW of silverleaf
nightshade berries are toxic.
Signs of poisoning include anorexia, salivation, abdominal pain, diarrhea, dilation of pupils, dullness, depression, weakness,
progressive paralysis, prostration and rarely death. Treatment generally is symptomatic and most animals quickly recover when
exposure is discontinued.
Ricinus communis (castor bean)
Castor bean is an ornamental or weed found mostly in southern states. Poisoning usually occurs when animals are fed concentrates
that are contaminated with castor-bean seeds. The toxin, ricin, inhibits protein synthesis (ribosome function) and also may
be antigenic, causing anaphylaxis in sensitive animals. The seeds or beans are highly toxic, especially to horses; 0.1 mg/kg
BW of well-chewed or ground seeds can be lethal.
Most animals develop clinical signs of poisoning 12 to 48 hours after ingestion. Signs include dull appearance, depression,
anorexia, thirst, weakness, colic, trembling, sweating, incoordination, difficult breathing, progressive CNS depression, fever,
bloody diarrhea, convulsions and death. Treatment is palliative to reduce absorption, including activated charcoal, cathartics
and supportive care. Poisoning often is fatal; many animals die without early intervention.
Convolvulus arvensis (field bindweed, morning glory — Photo 5)
Photo 5: Convolvulus arvensis (field bindweed, morning glory) is a noxious invasive perennial weed. It is prostrate, with
alternative leaves and white, funnel-shaped flowers. It has both seeds and extensive rhizome systems, making it difficult
Bindweed is an invasive, noxious weed that invades many pastures and paddocks. Horses grazing extensively on bindweed may
develop diarrhea, colic, gastrointestinal ulceration and intestinal thickening and fibrosis. The resinoid convolvulin and
several tropane alkaloids have been proposed as potential toxins. Little information is available on the required dose or
duration of exposure that will produce toxicity. Because poisoning appears to be irreversible, care should be taken to control
its spread, minimize its availability to horses and insure that other forages are available.
Juglans nigra (black walnut).
J. cinerea (butternut).
J. regia (English walnut).
Walnut shavings (>20 percent) used for bedding consistently causes laminitis in horses. Some also develop digestive problems.
Signs of laminitis develop in just over eight hours of exposure (depression, anorexia, stocking up, colic). Most animals recover
if exposure is discontinued.
Additional precautions to minimize absorption and minimize the effects of laminitis include washing legs, cooling fluids,
hoof wraps and pads and possibly anti-inflammatory agents.
Berteroa incana (hoary alyssum — Photo 6)
Photo 6: Berteroa incana (hoary alyssum) is a European weed that grows along roads and waste areas throughout North America.
It is an erect, branching annual that grows up to 1 m tall. The alternating leaves are narrow and smooth and the stems are
haired. Flowers are white and produce round, flattened seed pods that contain brown seeds.
Hoary alyssum is found in many northern states and Canada. It commonly grows in disturbed areas and can invade pastures and
hay fields. Most poisoning occurs in prepared and dried hay, within hours after exposure. Horses develop fever, distal limb
edema (stocking up), colic, bloody diarrhea, laminitis, abortion, dystocia, anorexia, dehydration and death. Post-mortem changes
are those of laminitis.
Treatment includes removing exposure, treating for laminitis and monitoring pregnant mares for abortion.