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What is Buffalo Bur Poisoning?

Buffalo bur contains a glycoalkaloid that affects the digestive tract and the central nervous system. The stems, leaves and unripe berries of buffalo bur are extremely toxic and can be fatal to all equines.

Buffalo bur is an aggressive weed that is native to the western plains east of the Rocky Mountains from North Dakota to Mexico. It can be found throughout the United States and also in other countries including Russia and Australia.

Buffalo bur is also known as mala mujer, horned nightshade, Colorado bur or by it’s scientific name, solanum rostratum. It is a creeping perennial vine that has dark green lobed leaves and yellow flowers. The plant has sharp, stinging spines. The seed pods are green and furry and are surrounded by sharp spines. Due to its thorny appearance, generally, buffalo bur is not eaten unless a horse is desperate for forage.

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Symptoms of Buffalo Bur Poisoning in Horses

Buffalo bur poisoning will affect the central nervous system of your horse, therefore it is important to seek immediate veterinary attention should you suspect that your horse has ingested buffalo bur. Things to watch for include:

  • Nausea
  • Abdominal pain
  • Diarrhea
  • Dilated pupils
  • Apathy
  • Drowsiness
  • Labored breathing
  • Dry mouth 
  • Trembling
  • Loss of coordination
  • Progressive weakness leading to paralysis
  • Prostration
  • Unconsciousness
  • Respiratory paralysis leading to sudden death

Causes of Buffalo Bur Poisoning in Horses

Buffalo bur contains the toxin solanine which is a glycoalkaloid. The highest concentration of solanine is found in the leaves, stems and unripe berries of the buffalo bur. When solanine is hydrolyzed, or mixed with water, the toxicity rises significantly.

Your horse is most likely to eat buffalo bur when turned into a pasture where the plants are abundant but other forage is limited. Depending on the soil and climate, the toxicity of the buffalo bur may be diminished or increased. Generally, buffalo bur that is found closer to the Rocky Mountains is less toxic than when found in other regions. The berries of the buffalo bur are extremely toxic when they are still green. When the berries are ripe and no longer green, they are almost harmless unless large quantities are eaten.

Diagnosis of Buffalo Bur Poisoning in Horses

Your veterinarian will begin their examination by checking your horse’s mouth. Many times when horses have been eating buffalo bur some of the spines or thorns are left behind on the lips and tongue. This will give your veterinarian a good clue as to what is ailing your horse.

A full examination will be conducted as well as a feed analysis. It is a good idea to have samples of your horse’s feed, including their hay, available for your veterinarian. A fecal exam, urinalysis and complete blood count will also be done to eliminate certain diseases.

Once it is determined that your horse is suffering from some form of plant poisoning and if the laboratory testing is inconclusive as to which plant, your veterinarian may go on the hunt. They will be searching for any poisonous plants that can cause the symptoms that your horse is presenting. Finding the exact cause of the plant poisoning will make it much easier for your veterinarian to treat your horse.

Treatment of Buffalo Bur Poisoning in Horses

After your veterinarian makes a definitive diagnosis of buffalo bur poisoning, a treatment plan can be put in place. Generally, horses will recover from buffalo bur poisoning if they are removed from the plants and then symptomatically treated. However, there are cases where more intensive treatments are needed because there are an excessive amount of toxins within the horse’s body.

In extreme cases, your horse may need to be hospitalized and given supportive care including fluid and nutritional therapy. In these cases, the symptoms are treated as they present and a parasympathomimetic drug is administered. This is usually pilocarpine and will relieve most clinical signs of buffalo bur poisoning.

Recovery of Buffalo Bur Poisoning in Horses

Once your veterinarian finishes assessing your horse, they will be able to give you a more exact prognosis. But, generally, horses that are diagnosed with buffalo bur poisoning have a good prognosis with limited to no long term effects. 

It is always easier to prevent buffalo bur poisoning from occurring rather than risking your horse’s health. You should never allow your horse to graze in a pasture where buffalo bur grows. If you notice that your pasture has buffalo bur, mow the plants down, dry them and burn them to keep seeds from being transported to other places and keep your pasture from becoming heavily infested. Buffalo bur is a very prolific seed producer. If you are unable to burn the dried plants then use an herbicide to treat them before the plants reach the fruiting stage.