Lambsquarters Poisoning in Horses

Lambsquarters Poisoning in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost
Lambsquarters Poisoning in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Lambsquarters Poisoning?

This annual herb is found in disturbed soils in many areas. Eaten in large amounts, they can cause sickness and death. The toxic parts of the plant are the leaves and the stems. The high levels of nitrates and oxalate content are thought to be responsible for most cases of poisoning. Symptoms usually show from between two to six hours after eating and if eaten in copious amounts can lead to the demise of your horse.

The lambsquarters plant contains high levels of nitrates and oxalates which causes a significant reduction in calcium uptake if your horse consumes a large amount.

Symptoms of Lambsquarters Poisoning in Horses

  • Respiratory problems such as breathing difficulties and shallow breathing 
  • Lack of energy to perform
  • Resistance to exercise 
  • Tremors
  • Weakness 
  • General distress and discomfort
  • Excessive drooling 
  • Abnormal gait 
  • Diarrhea 
  • Colic 


  • The type of poisoning from lambsquarters is not really understood that well although high concentrates of nitrates and oxalates are the cause
  • It depends on the stage of the plant growth as to the toxicity of the plant; with lambsquarters, a drought concentrates the poisons
  • If your horse is strong and healthy, he may be more resistant to the toxin than an older or younger horse 
  • Caution in early spring when grazing as weeds outcompete pasture 
  • Considered dangerous in all seasons


Causes of Lambsquarters Poisoning in Horses

  • Lambsquarters can be a problem when the plants grow under drought conditions and high nitrogen fertilisers where they will accumulate nitrates
  • Because of hunger in over grazed paddocks or drought conditions your horse will be more susceptible to eating a new plant 
  • Lack of clean water makes it hard for your horse to metabolise and excrete poison 
  • Improving your pasture grazing by rotational or strip grazing will help


Diagnosis of Lambsquarters Poisoning in Horses

In nearly all cases of poisonings, your horse is going to require immediate veterinary assistance. Look around your pasture or the area where your horse was stabled to isolate any unusual or possible plants that may have caused the problem. In some pastures, any balding patches of earth  are an open invitation for rogue weeds to take over and once they have a hold they can spread quickly through the field. If you suspect a plant, remove it and show the veterinarian in order to get it identified so that you know what you are dealing with. 

Most horses will not usually graze toxic plants because of their unpalatable taste, but occasionally if feed is in short supply or they are lacking certain minerals in their diet, they may experiment with unknown plants which is not a good thing. Although the symptoms of the toxic weeds can be similar, the methodology of treatment can vary. The veterinarian will evaluate the clinical signs that your horse is exhibiting such as breathing difficulties and drooling, which can confirm the diagnosis.

Keep in mind that the age of your horse and his health can influence the way they deal with the poisoning. If your horse is a mature horse but has a damaged liver or kidneys or is suffering from parasitic infections, the immune system will be less capable of coping with additional stress. Therefore, blood tests and a fecal sample may be taken by the veterinarian to verify organ function or the presence of parasites.



Treatment of Lambsquarters Poisoning in Horses

One way that your veterinarian may treat your horse once they have diagnosed the poisoning is to attempt to wash out your horse’s stomach in hopes of removing the offending plant that was consumed. Activated charcoal can be used to absorb the poison to prevent it being absorbed into your horse’s body. Obviously, it depends on the time factor of how long it has been between eating the lambsquarters and noticing your horse is not well. The quicker the time between the two the better. The less time the poison has to get into the system the better. 

Laxatives may be an option to use if the time factor was short, it may help to speed the plant material through the system and expel it quicker. It is easier to prevent this happening to your horse than treatment and aftercare. By maintaining close pasture control and having a program to eradicate weeds that infiltrate from windblown sources and take hold, it will be more economical and less stressful than dealing with a loved equine that is suffering from the toxic effects of the plant. 



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Recovery of Lambsquarters Poisoning in Horses

Recovery depends on the amount of plant eaten, and the time since it was eaten. The earlier it is noticed, the easier on your horse. If your horse has had its stomach washed, or other treatments, it may be feeling a bit low and it would be best to keep it stabled and cared for with quality feed and clean water until it recovers. Your veterinarian will be able to advise about diet and exercise, and will probably come to visit regularly until your horse shows a full recovery. Management relies on a commitment to care of your pastures and being ever vigilant to noticing noxious weeds that creep in. it also requires careful use of herbicides and fertilisers used on the grasslands, and allowing adequate time for the absorption into the field prior to grazing.



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