Feed fresh and you should be ok, pigs are pretty cute about what to eat.
I have seen "ragwort is poisonous to pigs" mentioned several times in forums, but so far have found no authoritative source or studies into this. Clearly horses are highly sensitive to it, but I don’t know what dose would harm a pig. For instance alcohol is poisonous to humans!
If anyone knows of a written text from a “reaserch” source this would be good to share with forum members.
I certainly know of people keeping pigs in areas that have (or more accurately after the pigs have been there had) ragwort with no issues.