Ok, so the solution for sheep is threefold.
1. Garlic acts as a natural dewormer
2. mix DE in with the minerals at a rate of 1/4 DE to the mineral mix.
3. Rotate them on pasture, and don't let them stay on the same pasture more than 21 days. 1 week is much better. then rest the paddock for at least 2 months for the worms to die off.
learned this from Skyline Farms