Ragwort poisoning is actually quite rare. You only really need worry about hay. Animals naturally avoid toxic plants. It takes far far more than a mouthful to poison a horse. The problem is that some people have wanted to talk up the problem for their own profit.
Did you know that the toxins in ragwort occur in lots of other plants? 3% of the world's plants contain them.

Several myths have been repeated in this thread. not only does it take far far more than a mouthful to do damage it most certainly isn't illegal to have it growing on your land.


See the following sites
Ragwort - Is it as bad as you think?

It gives scientific references for every point and gives a useful list of myths.

and

Ragwort, Myths and Facts

The latter site is written by a Dutch horse owner. ( This is the English language version)
She was a member of a group that wanted to eradicate ragwort because they believed it was seriously dangerous, but she asked some scientists for help and they explained that most of the stories going around were false. She was so upset by the untruths that were being told that she wrote the site to correct all the false stories.