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American pokeweed (Phytolacca americana) is a common, highly toxic weed that grows in most areas of the Unites States, particularly along the East Coast. It is native to parts of North America, South America, New Zealand, among other places. Sometimes called inkberry, pokeweed is a beautiful plant with small white flowers and large purple berries containing a pink-colored juice.
Pokeweed is toxic to humans and most animals, particularly horses and cattle, but causes significant harm only when consumed in large amounts. This herbaceous perennial is often mistaken for another type of toxic plant, nightshade; however, the two plants are quite dissimilar in appearance. Pokeweed may reach heights of 8-10 feet, while nightshade tops out at two feet. Nightshade is green in color, while pokeweed stems are reddish-pink. While all parts of pokeweed are toxic to horses, the roots and seeds contain the largest amounts of the toxin compounds, phytolaccatoxin, pokeberry genin and jaligonic acid. The berries have the lowest concentration of poison, though in large amounts, horses may experience respiratory distress and some colicky symptoms following consumption. Eating the stems, leaves and roots may cause significant gastrointestinal illness, including colic and bloody diarrhea. In rare cases, especially when horses are relying on pokeweed during times of drought, horses have displayed symptoms such as uncoordinated movements, tremors, irregular heartbeat, full body sweating, and even sudden death.
As with most poisonous plants, horses do not typically find pokeweed to be palatable. While some horse owners insist that their horses do not mind its pungent taste, pokeweed is typically only eaten when healthy forage is unavailable. Come spring, it’s green shoots may attract some horses, but, after experiencing burning to the tongue and symptoms of gastric distress, most leave the pokeweed alone. Unfortunately, during a time of drought, pokeweed is strong enough to endure the dry conditions, and may appeal to hungry livestock. The longer the pokeweed plant endures, the stronger its toxicity. As always, if you think your horse has consumed anything toxic, contact your veterinarian immediately.
Pokeweed (Phytolacca americana), a highly toxic plant native to the eastern United States, can cause gastrointestinal and respiratory distress in horses.
As with most plant poisonings, diagnosis is based upon a generalized group of gastrointestinal symptoms such as diarrhea. In the case of pokeweed, some horses may experience dangerous, if not fatal, respiratory distress typified by heavy breathing, gasping, flaring of the nostrils and snorting. Some horses will have staining around the lips and nose due to consuming the pokeweed berries. Necropsy will be conducted in the case of death.
The easiest way to develop a diagnosis of plant poisoning is by knowing the plants and trees that grow on your property, and noting the horse’s eating patterns. If your horse is having diarrhea or gastrointestinal distress, it’s likely tied to the area your horse is doing the predominance of grazing. Your veterinarian may ask to see plant samples.
In most cases, treatment will be supportive in nature and focus on resolving dehydration and stomach upset. IV/subcutaneous fluids are usually given, as well as medication (such as Pepto Bismal and simethicone) to resolve cramping and bouts of diarrhea. In most cases, symptoms resolve within 24 hours. Respiratory distress may be alleviated with administration of supplemental oxygen. Remove hay and grain per the veterinarian’s instructions. Symptoms typically recede within 24-36 hours.
Avoid future instances of poisoning by increasing your awareness of the trees and plants that inhabit the pasture. Remove any suspicious plants. Check for invasive weeds and seasonal plants. Do not forget to examine grass-clippings that may blow over from other properties. Bring samples of unknown plants to the veterinarian. Have hay and feed tested for signs of contamination.
For the safety of adults, children and animals, pokeweed should always be removed from pastures. A careful hand-pulling may be all that is necessary in cases of little growth, but since the plant is toxic to humans, wear gloves. Good pasture management, including consistent summer mowing and weed removal, will usually suffice in keeping pokeweed under control. Owners report that pokeweed growth seems to occur overnight, so daily weed-walks are recommended to insure safety. Pokeweed grows wildly throughout horse pastures, and even crosses the fence line where horses reach for forage. Effective pasture maintenance will account for this growth pattern.
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