What plants found in fields are poisonous for horses?

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Did you know that some of the plants that grow in our fields and pastures can be poisonous for horses? Here is some essential information on how to identify them and the symptoms they cause.

Poisonous plants for horses: identifying them to avoid accidental poisoning

There are around seventy species of plants that are more or less poisonous for horses. Fortunately, horses, these noble and intelligent animals, generally know how to recognise plants that are not good for them. However, this is not always the case for the humans looking after them. Intoxication or poisoning by plants can occur if a plant is inadvertently incorporated into the stable fodder. Once cut and dried, these plants are more difficult for the horse to identify, and can sometimes be even more poisonous.

As it is hard to remember the entire list of these plants, a smartphone app that lists the seventy most dangerous plants for your horse is available to help you: the Agroscope Swiss National Stud has developed the Toxiplant app, available free of charge from Apple Store, with photos of the plants, typical symptoms of poisoning, and essential first aid.

The most poisonous plants for horses in fields

While some plants will only cause digestive discomfort, other plants are much more dangerous and can lead to death if they are ingested in too great a quantity. As horses cannot vomit, once the plant has been swallowed, there is no going back! As such, be attentive to the poisonous plants that your horse may be exposed to. Here is an excerpt of the most toxic plants with their symptoms:

  • Absinthe has dramatic consequences, especially on mares in foal, from 500 g (causes abortion);
  • Ranunculaceae: aconite, pulsatile anemone, adonis, buttercups, and ficaria are all poisonous for horses with more or less serious consequences if ingested; Aconite is fatal from 300g, and causes paralysis of the pharynx, diarrhoea, and anuria;
  • Hellebores: 60g will cause death after the onset of cramps and inevitable paralysis;
  • Spurge is deadly from 50g, but horses rarely go near it;
  • Foxgloves are dangerous from 200g of fresh leaves, but 25g of dried leaves is sufficient to cause fatal cardiac arrest. Initial symptoms are bloody diarrhoea and dizziness;
  • Belladonna is toxic from 10g, causes convulsions and can lead to death from 120g;
  • Henbane is toxic from 10g, fatal from 125g, and causes convulsions;
  • Black nightshade contains alkaloids in its seeds. It causes irritation of the mucous membranes and profuse diarrhoea.

Atypical myopathy caused by the sycamore

Atypical myopathy (AM) is one of the diseases of pastures that is very present in France and Europe. Usually fatal (70% of cases), this disease is characterised by severe degeneration of the postural, respiratory and cardiac (myocardial) muscles.

In the majority of cases, the symptoms appear suddenly: difficulty or inability to stand up, muscle stiffness, tremors, sweating, very dark urine (coffee colour), congestion of the mucous membranes.

The cause of the disease was clearly identified in 2013: it is caused by the ingestion of a toxin, hypoglycin A. This toxin is found in the flowers, fruit (also called samaras), and seedlings of the sycamore (Acer pseudoplatanus).

The disease generally peaks in the spring, when seeds germinate, producing seedlings, and in the autumn. The wind disperses the samaras, which increases their proliferation in the surrounding hedges and thickets.

Depending on the season, also watch out for crocuses and daffodils in spring, common ragwort and poppies in summer, and brugmansia and autumn crocuses. These wild flowers nicely decorate pastures but are the enemies of horses.

In general, always carefully choose the plants that will make up your horse’s feed crops.

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