Sometimes, when faced with a sea of yellow it must be a little tempting to hack it all down and start again.
STOP RIGHT THERE!
There are 2 main reasons why this is a dreadful idea and will actually make things worse. Admittedly, by cutting down the plants before they seed, you will prevent the spread of newly formed seeds, but when a ragwort plant base is damaged, and this can also happen when they get damaged when horses trample them, it can cause the plant to change its habit from bi-ennial to perennial- that it, it will return year after year, and not die at the end of its 2 year cycle. Not really what you had in mind was it?
How were you thinking of cutting the ragwort down? If you truly are faced with a forest of the stuff, it may be that you are thinking of cutting by machine, a ride on mower, tractor etc. If you have to cut it, do it one plant at a time and bag it as you go.
The most important reason why cutting the down ragwort is not a good idea is that usually people choose this option because there is so much and therefore use the mechanical option. What happens to all the chipped and chopped up bits? There they lie on the pasture just waiting to be eaten when they've wilted and lost their bitter taste. Once it's all wilted or dead, it won't taste so bad, but will be just as deadly to your horse. I'm sure that often, the horses will be kept off the land, but there will still be plenty of plant debris that will be consumed once they return. Did you know that the Ragwort Plant doesn't have to actually shed the seed naturally for the seed to germinate and grow? Once the Ragwort Seeds hit the floor, its open season! It is all a bit of a disaster waiting to happen.
If you do wish to remove Ragwort by digging, please make sure that you remove all plant debris from the field and dispose of it properly.