The problem with ragwort is it is a tough sod of a weed. It is more poisonous dried than it is fresh and the seeds can stay dormant in the ground for 20 years before they grow!

You want to get it before it starts flowering, and a ragfork is the best at getting it up. Also it is a myth that sheep are immune to it. It is not worth taking the risk as it is a horrible way for an animal to go as its liver shuts down.