The only ways to stop dog worms getting into sheep are
a) keep the dogs worm free by worming
b) pick up all dog poo
c) don’t allow dogs on the ground the sheep will graze
You cannot treat the ground and you cannot treat the sheep.
We use a+b.
While we are on the subject - does anyone know how long the ground would remain contaminated? We have one area where our holiday guests walk their dogs, but are thinking about bringing some of this back to grazing. We don’t know, however, how long we need to give it after the last dog walks there before we let the livestock on.