Pearce Pastures
Barn Babe
There are some plants that are listed as toxic that would have to be ingested in large quantities for a serious reaction. Then there are others that only require a small amount for an issue to arise (Azalea, Rhododendron). Buttercup is a toxic plant but 1) if they have plenty of browse, they might not touch it or may not eat enough for a reaction and 2) you could possibly have a few kids go out with gloves and a wheelbarrow and rip it out by the roots and reduce the volume of it in your pasture.