At this time of the year we see the emergence of many weeds amongst our pastures, many of which can have negative impacts on horse health. Although most weeds are generally avoided by horses, in tough dry conditions horses may consume weeds.

Paterson’s Curse (Echium plantagineum)

Paterson’s Curse (Echium plantagineum) is a common weed in our area, seen to paint our pastures purple with its flowers in late spring. Unfortunately, this weed is toxic to horses, containing compounds called pyrrolizidine alkaloids. Chronic poisoning from these toxic compounds in horses is the most common effect, resulting from grazing small amounts over time. This leads to damage of the liver and signs such as weight loss, decreased appetite, lethargy and photosensitisation (redness and swelling of the skin) may be seen. Signs may be seen years after grazing pasture with Paterson’s curse. In horses with suspected poisoning, liver function can be assessed by blood testing.

Flatweed (Hypochoeris radicata)

Flatweed (Hypochoeris radicata) may look like a harmless yellow dandelion but unfortunately has been connected to a devastating disease in horses. It is associated with stringhalt – a disease that damages long nerves in the body and commonly affects the hind legs of horses, resulting in sudden uncontrolled exaggerated flexion of one or both legs. Cases in horses range from mild (subtle changes when the horse steps back) to severe (flexion of hind legs so exaggerated that they may hit the belly when moving). Muscle wastage and paralysis of the larynx causing “roaring” may also be seen. Unfortunately the exact toxin in the plant causing this disease is still unknown.

If you suspect these weeds may be in your pasture or are worried your horse may be affected please contact us at the clinic on (02) 6238 1133 for advice.