What is the best herbicide to spray on pastures to attempt to kill some pretty thick patches of thistles? It would be best if the herbicide has no grazing restrictions for non-lactating animals but I could deal with it if I had to pull the animals out for a week or so if need be. There are some soybean fields relatively close to these pastures so I guess drift is somewhat of a concern but I assume anything worth spraying will have some 2,4D in it?

Is Grazon P+D the best choice or are they better ones out there?