On Fri, 10 Aug 2007 20:25:17 +0100, Robert
wrote:

snip[

A really good, balanced source of information on the pros and cons of
ragwort is the Natural England/English Nature information note,
primarily aimed at farmers and land managers but very useful to anyone
interested.
http://tinyurl.com/26kwaw

Which contains the following:

Many grazing animals are at risk from the toxic effects of consuming
ragwort by grazing the plant and consuming it in forage. Horses are
especially susceptible. Cattle, sheep, goats and pigs, especially of
adapted breeds, will avoid eating ragwort when it is growing but are
more at risk when plants are wilted or dying. Signs of ragwort
poisoning may be slow to develop and may not become apparent for
several days, weeks or months. Signs may appear after consumption of
the plant has ceased. Poisoning can develop quickly and animals can
die within a few days of showing clinical symptoms. Liver damage is
irreversible and there is no effective treatment