Page 804 - The Veterinary Care of the Horse

Ragwort (Senecio jacobaea – tansy ragwort, and Senecio vulgaris

– groundsel)
VetBooks.ir The tansy ragwort plant has a 2-year life cycle. In its first year, it has a dark green rosette

form that grows amongst the grass. In the second year it flowers and grows to between 30 cm
and 1 m (1 ft and 3 ft) high. The characteristic yellow flowers of the ragwort plant are a

common sight on horse-sick pastures and roadsides during the summer months (July–
September) (Figure 17.21). The plant contains toxic pyrrolizidine alkaloids which cause
irreversible liver damage. In the UK, the spread of this plant is meant to be controlled by law.

Figure 17.21 Ragwort

The growing plant tastes very bitter and horses usually avoid it unless other grazing is
scarce. However, once it is cut and dried, the plant becomes palatable. It is most dangerous

when baled with the hay or if pulled up and left to wilt where horses are able to eat it.

CLINICAL SIGNS

The effects of the alkaloids are cumulative and signs are not usually seen until some time

after consumption of the plant begins. In some cases the signs are delayed and may not