Cows, Cornstalks and Nightshade
With corn harvest in full swing and grass pasture grazing season winding down, it is that time of year when beef producers start sending cattle out to cornstalks; an economical way to extend the grazing season. While agronomic tillage practices and herbicide programs have reduced problem broadleaf weeds and grasses, nightshade seems to be a hard one to control. Nightshade can be toxic to animals (livestock and pets), and especially horses. While not a high risk, still a risk that beef producers should be aware of and manage cattle appropriately.
Black nightshade is a low-branching annual, 1 to 2 feet tall with triangular stems that bear oval, thin-textured, alternate leaves with wavy margins. The tiny white flowers, borne in drooping clusters on lateral stalks between the leaves, resemble tomato flowers. The berry fruit is green when immature, purplish-black when ripe. Bitter nightshade resembles black nightshade except that it is a perennial with climbing stems, the lower leaves are lobed at the base, the flowers are purple and the ripe fruit is red. Silverleaf nightshade, another perennial, gets its common name because of its silvery appearance caused by the numerous fine hairs. The stems and parts of the leaves have short stiff spines, and flowers appear at the end of branches and are pale to deep blue or lavender in color. Horse nettle, a perennial, has yellowish spines on its stem and leaves, and sometimes is hairy. Petals are united with 5 points at the margin, and flowers are light purple to white. Other nightshade family members include: buffalo bur, ornamental Jerusalem cherry, eggplant and the common white potato.
Nightshades commonly grow in fields, open woods, waste areas, pastures, along roadsides and around farm buildings. Nightshade berries are eaten by birds and deer and are spread through their droppings. This makes the plant virtually impossible to isolate and eliminate.
All parts of the plant contain toxic glycoalkaloids, especially the berries. The highest concentration of toxins is in immature berries. The plant is not that palatable and generally is eaten when other forage is not available. Curious or bored pets are particularly at risk. The plant may be a contaminant in hay, where it will still have some reduced toxicity.
Classical signs of nightshade problems are in the gastrointestinal tract and the central nervous system, i.e. abdominal pain, vomiting, diarrhea, incoordination, weakness, difficulty breathing, depression, convulsions and death is possible, although rare. Contact a veterinarian immediately if nightshade poisoning is suspected.
Some management options to reduce nightshade-poisoning risk:
Defer grazing those cornstalks with higher levels of nightshade
Keep a closer watch on livestock grazing nightshade invested areas
Allow hard frosts to wilt plants and cause berries to drop
Do not over graze nightshade infested cornstalks
Fence livestock out of areas dense with nightshade
A good website for information and color photos of nightshade is: http://www.vth.colostate.edu/poisonous_plants/.
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