Signs and lesions of nightshade poisoning:

  • Labored breathing and expiratory grunt
  • Salivation and nasal discharge
  • Body temperature may be slightly elevated
  • Yellow discoloration of the skin may occur in chronic poisoning
  • Apathy, drowsiness, progressive weakness, paralysis, and trembling
  • Increased heart rate
  • Fat may be yellowed and gelatinous
  • Gall bladder may be distended
  • Gastrointestinal irritation including inflammation, hemorrhage and ulceration

There are several species of nightshades that are toxic to horses, cattle, swine, sheep and poultry. The genus includes annual and perennial herbs and shrubs that can be found throughout the U.S.

The principal species that serve as examples of the genus are black nightshade (Solanum nigrum), silverleaf nightshade (S. eleagnifolium), and buffalo burr (S. rostratum). Black nightshade is an introduced herbaceous annual weed that can be found growing mostly on disturbed soils and waste areas in the eastern U.S. and into the Midwest. Silverleaf nightshade is a perennial with long creeping rootstocks. Buffalo burr is an annual native to the Great Plains and introduced to the West Coast.

The toxins include a combination of a number of sugars and at least six different steroidal amines combined to form a variety of glycoalkaloids. One example is the toxin solanine. Potatoes are included with this group because the vines are toxic and tubers that have been exposed to light can be toxic to livestock. Drying does not destroy the toxin.

Nightshade species are not very palatable to livestock. However, these plants often grow as weeds in hay and silage crops and small grains where they can be harvested with the crop and then fed to livestock.

Where and when nightshades grow:

Black nightshade (both the native and introduced varieties) is an annual 6 in. to 3 ft. tall. Leaves are simple, ovate to lanceolate, entire to sinuate-dentate. Flowers are white; berries are black when ripe. It grows peripherally in moist areas of fields and pastures of disturbed loamy or gravelly soils throughout the U.S.

Silverleaf nightshade is a perennial that grows 1 to 3 feet tall with white, hairy leaves and stems. Leaves are simple, thick, lanceolate to linear, entire to sinuate. Stems and ribs usually have short stiff spines. Flowers are violet or blue; berries are yellow or orange. Silverleaf nightshade grows in fields, pastures, and roadsides from Missouri to Texas and California.

Buffalo burr is an annual spiny weed 1-2 ft. tall. Leaves are irregularly round-lobed or once or twice pinnately deeply lobed; veins are spiny. Flowers are yellow, and the berries are enclosed. Native to the Great Plains and introduced to the West Coast, buffalo burr grows in old fields, overgrazed pastures and roadsides.

How nightshades affect livestock:

Nightshades are generally unpalatable and are not grazed by livestock except under the stress of overgrazing or in contaminated hay and grain. Poisoning by this group of plants does not always end in death. In acute poisoning, the nervous symptoms develop rapidly. Death or recovery occurs within a few hours to 1 or 2 days. Death apparently is related to the paralysis. Chronic poisoning is accompanied by emaciation, rough hair coat, anorexia, constipation and ascites.

How to reduce loss:

Losses can be kept at a minimum by good pasture management and weed control. Harvested forage such as hay, grain or silage can be contaminated with nightshades. Contaminated forage can be fed if it is diluted (mixed) with nightshade-free forage: an on/off feeding strategy should be used. Animals being fed this diluted forage should be kept under close surveillance and immediately removed from the contaminated feed if signs of poisoning appear. Submit a sample to the Poisonous Plant Research Lab for analysis.