Sheep preferentially graze ragwort over grass. So they are continually biting off the growing points, killing the plant, but not taking in any significant amount of the toxin. You don't even have to graze it tight. In the example above, the 30 acres was for cattle grazing all summer so had a decent depth of sward on it. No good turning the sheep on when you can see it of course. You have to have them on from new year.Hmm. Surely sheep get a build up of toxins in the end? It's a dry field making it very attractive to extend the back end grazing for yearling cattle. So could I really keep it bitten down hard with ewes and shearlings until August, allow a recovery of grass growth and safely graze cattle until Christmas?
Hence my weed wiper suggestion, I know a man who hires them and travels out that way, its supposed to work well.spot spray at floret stage with headland polo ( not technically allowed on hls ) or bit labour intensive. I know some one who dipped a gloved hand with glysophate and applied to weeds that way .not technical spraying.