ok, interesting in case anyone else ever looks for something... from 'gardenbanter.co.uk':
'No actually it isn't s poison that is stored in the liver. The damage is
cumulative but the poison disappears. There is actually very very little
risk from ragwort at all. It can cause poisoning in very very rare cases
but that is usually caused by it being present in hay.
There are a whole series of thresholds before any damage is done at all so,
contrary to what you may have read, small doses have no effect at all.
I know that there is a lot of stuff around telling you that Ragwort is
dangerous but it all comes from a few dodgy sources who have been
publicising it for their own interests. It is almost a classic example of
how to deceive people with bad science. Since I got interested in this I
have spent a lot of time checking scientific papers to get at the truth.
Some of the bad science has even got repeated in government press releases!
For more details on the science see www.ragwortfacts.com/
There is little risk to animals like rabbits and Guinea pigs for unless it
is dried it tastes and smells so awful to them that they won't touch it.
In fact one of the signs that a place is being overgrazed, by rabbits or
anything else, is that ragwort its growing there in abundance.'
Will keep an eye on them nonetheless!