Don't forget to get good advice regarding worming your horses successfully and making sure that the pasture is as good as you can make it.
As soon as you see any sign of this yellow flowering plant, please remove it with its roots intact and burn it. Never leave pulled up plants in the field or near it and if you neighbour has lots growing near your horse's field, it will go to seed and, depending on which way the wind blows, could affect your horse's grazing.
It is widely accepted that the plant loses its unpleasant taste when it dies but it is still just as dangerous. This means that ragwort found in hay or haylage, or leaves that have fallen off a plant in the field and died, can very easily be eaten unknowingly and will be just as harmful as a living plant.
After flowering, most of the plants die and the seeds germinate in the area where the mature plant had been. One plant can produce many thousand of seeds which are covered with a downy substance so they can be easily dispersed by prevailing winds. They can also be spread by water or by you and your animals.